Difference between revisions of "RPi Low-level peripherals"

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==Introduction==
 
==Introduction==
In addition to the familiar USB, Ethernet and HDMI ports, the R-Pi offers lower-level interfaces intended to connect more directly with chips and subsystem modules. These GPIO (general purpose I/O) signals on the 2x13 header pins include SPI, I2C, serial UART, 3V3 and 5V power. These interfaces are not "plug and play" and require care to avoid miswiring. The pins use a 3V3 logic level and are not tolerant of 5V levels, such as you might find on a 5V powered Arduino. Not yet software-enabled are the flex cable connectors with CSI (camera serial interface) and DSI (display serial interface), and a serial link inside the HDMI connector called CEC. (consumer electronics control)
+
In addition to the familiar USB, Ethernet and HDMI ports, the Raspberry Pi offers the ability to connect directly to a variety of electronic devices. These include:
 +
* Digital outputs: turn lights, motors, or other devices on or off
 +
* Digital inputs: read an on or off state from a button, switch, or other sensor
 +
* Communication with chips or modules using low-level protocols: [http://www.corelis.com/education/SPI_Tutorial.htm SPI], [http://i2c.info/ I²C], or [https://learn.sparkfun.com/tutorials/serial-communication serial UART]
  
==General Purpose Input/Output (GPIO)==
+
Connections are made using GPIO ([https://en.wikipedia.org/wiki/General-purpose_input/output "General Purpose Input/Output"]) pins. Unlike USB, etc., these interfaces are not "plug and play" and require care to avoid miswiring. The Raspberry PI GPIOs use 3.3V [https://learn.sparkfun.com/tutorials/logic-levels/all logic levels], and can be damaged if connected directly to 5V levels (as found in many older digital systems) without level-conversion circuitry.
[[File:GPIOs.png|thumb|254px|right|The layout of the Raspberry Pi Revision 1 P1 pin-header seen from the top, containing pins useable for general purpose I/O. Colour coded to the table. [https://sites.google.com/site/burngatehouse/home/drawings/GPIOs2.gif Source] ]]
+
  
General Purpose Input/Output (a.k.a. GPIO) is a generic pin on a chip whose behavior (including whether it is an input or output pin) can be controlled (programmed) through software.
+
Note that no analogue input or output is available. However, add-on boards such as the [[Rpi Gertboard]] provide this capability.
  
The Raspberry Pi allows peripherals and expansion boards (such as the [[Rpi Gertboard]]) to access the CPU by exposing the inputs and outputs.
+
=== Links ===
 +
* For further specific information about the Raspberry Pi's BCM2835 GPIOs, see: [[RPi BCM2835 GPIOs]].
 +
* Sample code in many different languages is on the [[RPi GPIO Code Samples]] page
 +
* To connect devices to the serial port (UART), see the [[RPi Serial Connection]] page.
 +
* Sample circuits for interfacing the GPIOs with other electronics are shown on the [[RPi GPIO Interface Circuits]] page.
 +
<br>
 +
= General Purpose Input/Output (GPIO) =
  
For further general information about GPIOs, see:[http://en.wikipedia.org/wiki/GPIO the wikipedia article].
+
== Model A and B (Original) ==
  
The production Raspberry Pi board has a 26-pin 2.54&nbsp;mm (100&nbsp;mil)<ref>http://www.raspberrypi.org/forum/features-and-requests/easy-gpio-hardware-software/page-3/#p31907</ref> expansion header, marked as P1, arranged in a 2x13 strip. They provide 8 GPIO pins plus access to I²C, SPI, UART), as well as +3.3&nbsp;V, +5&nbsp;V and GND supply lines. Pin one is the pin in the first column and on the bottom row. <ref>http://www.raspberrypi.org/archives/384</ref>
+
=== P1 Header ===
 +
 
 +
{|
 +
|-
 +
| [[File:Pi-GPIO-header-26-sm.png|thumb||right|26-pin GPIO header layout. Note that Rev 1 PCBs had different assignments for pins 3, 5, and 13]]. | [[File:RPi_P1_header.png|thumb|450px|left]]
 +
|}
 +
 
 +
The Raspberry Pi Model A and B boards have a 26-pin 2.54&nbsp;mm (100&nbsp;mil)<ref>[http://www.raspberrypi.org/forum/features-and-requests/easy-gpio-hardware-software/page-3/#p31907 raspberrypi.org]</ref> expansion header, marked as P1, arranged in a 2x13 strip. They provide 8 GPIO pins plus access to I²C, SPI, UART), as well as +3.3&nbsp;V, +5&nbsp;V and GND supply lines. Pin one is the pin in the first column and on the bottom row. <ref>[http://www.raspberrypi.org/archives/384 raspberrypi.org]</ref>
 +
 
 +
'''Revision 1 PCBs:''' Raspberry Pis with a revision 1 PCB (September 2012 or earlier) have a different pin assignment on the P1 connector:
 +
* P1 pin 3 is GPIO 0 / SDA0 (not GPIO 2)
 +
* P1 pin 5 is GPIO 1 / SCL0 (not GPIO 3)
 +
* P1 pin 13 is GPIO 21 (not GPIO 27)
 +
 
 +
Revision 1 PCBs also do not have the P5 header (see below). See [http://www.raspberrypi.org/archives/1929#comment-31646 this discussion] for more details of the changes between Rev 1 and Rev 2 PCBs.
 +
 
 +
=== P2 header ===
 +
The P2 header is the VideoCore JTAG and used only during the production of the board. It cannot be used as the ARM JTAG <ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894</ref>. This connector is unpopulated in Rev 2.0 boards.
 +
 
 +
[[File:RPi_P2_header.png]]
 +
 
 +
Useful P2 pins:
 +
* Pin 1 - 3.3V (same as P1-01, 50 mA max current draw across both of them)
 +
* Pin 7 - GND
 +
* Pin 8 - GND
 +
 
 +
=== P3 header ===
 +
The P3 header, unpopulated, is the LAN9512 JTAG <ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894</ref>.
 +
 
 +
[[File:RPi_P3_header.png]]
 +
 
 +
Useful P3 pins:
 +
* Pin 7 - GND
 +
 
 +
=== P5 header ===
 +
The P5 header was added with the release of the Revision 2.0 PCB design.
 +
 
 +
[[File:RPi_P5_header.png]]
 +
 
 +
===P5 Header pinout, top row===
 +
As seen from the back of the board:
 +
{| border="1" style="text-align:center;"
 +
| '''Pin Number''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 +
|-
 +
| P5-01 || bgcolor="red" | <span style="color:white">5V0</span> || Supply through input poly fuse
 +
|-
 +
| P5-03 || bgcolor="lime" | GPIO28 || || bgcolor="cyan" | I2C0_SDA || ALT2 = PCM_CLK
 +
|-
 +
| P5-05 || bgcolor="lime" | GPIO30 || || || ALT2 = PCM_DIN ALT3 = UART0_CTS ALT5 = UART1_CTS
 +
|-
 +
| P5-07 || bgcolor="black" | <span style="color:white">GND</span>
 +
|}
 +
 
 +
===P5 Header pinout, bottom row===
 +
As seen from the back of the board:
 +
{| border="1" style="text-align:center;"
 +
| '''Pin Number''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 +
|-
 +
| P5-02 || bgcolor="orange" | 3.3&nbsp;V || 50&nbsp;mA max (combined with P1)
 +
|-
 +
| P5-04 || bgcolor="lime" | GPIO29 || || bgcolor="cyan" | I2C0_SCL || ALT2 = PCM_FS
 +
|-
 +
| P5-06 || bgcolor="lime" | GPIO31 || || || ALT2 = PCM_DOUT ALT3 = UART0_RTS ALT5 = UART1_RTS
 +
|-
 +
| P5-08 || bgcolor="black" | <span style="color:white">GND</span>
 +
|}
 +
 
 +
[[File:Male-slanted2small.jpg|150px|thumb|left|Slanted P5 header]]
 +
 
 +
Note that the connector is intended to be mounted on the bottom of the PCB, so that for those who put the connector on the top side, the pin numbers are mirrored. Pin 1 and pin 2 are swapped, pin 3 and 4, etc.
 +
 
 +
An alternative way to attach this header is on top, [http://raspi.tv/2013/the-leaning-header-of-pi5a-how-best-to-solder-a-header-on-p5 at a slant away from the P1 header.]
 +
 
 +
The new header can provide a second I²C channel (SDA + SCL) and handshake lines for the existing UART (TxD and RxD), or it can be used for an I2S (audio codec chip) interface using the PCM signals CLK, FS (Frame Sync), Din and Dout.
 +
 
 +
Note that the connector is placed JUST off-grid with respect to the P1 connector.
 +
 
 +
=== P6 header ===
 +
The P6 header was added with the release of the Revision 2.0 PCB design.
 +
 
 +
[[File:RPi_P6_header.png]]
 +
 
 +
===P6 Pinout===
 +
{| border="1" style="text-align:center;"
 +
| '''Pin Number''' || '''Pin Name Rev2''' || '''Hardware Notes'''
 +
|-
 +
| P6-01 || RUN || Short to ground to reset the BCM2835
 +
|-
 +
| P6-02 || bgcolor="black" | <span style="color:white">GND</span>
 +
|}
 +
 
 +
A reset button can be attached to the P6 header.<ref>[http://raspi.tv/2012/making-a-reset-switch-for-your-rev-2-raspberry-pi raspi.tv]</ref> Momentarily shorting the two pins of P6 together will cause a soft reset of the CPU (which can also 'wake' the Pi from halt/shutdown state).
 +
 
 +
== Model A+, B+ and B2 ==
 +
 
 +
{|
 +
|-
 +
| [[File:A_plus_hdr_sm.jpg|thumb|Model A+]] || [[File:B_plus_hdr_sm.jpg|thumb|Models B+, B2]] || [[File:Pi-GPIO-header.png|thumb|Connector pinout]]
 +
|}
 +
 
 +
<br>The Raspberry Pi Model A+ and B+ boards, and the Pi 2 Model B, have a 40-pin header marked J8, arranged as 2x20 pins. The first 26 pins are the same as P1 on the A/B boards, with the remaining 14 pins providing additional GPIO and ground pins, and an EEPROM ID feature for auto-configuration with add-on "HAT" boards.<ref>[http://www.raspberrypi.org/wp-content/uploads/2014/04/bplus-gpio.png raspberrypi.org]</ref>
 +
 
 +
== Interfacing with GPIO pins ==
  
 
'''GPIO voltage levels are 3.3&nbsp;V and are not 5&nbsp;V tolerant. There is no over-voltage protection on the board''' - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board.
 
'''GPIO voltage levels are 3.3&nbsp;V and are not 5&nbsp;V tolerant. There is no over-voltage protection on the board''' - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board.
  
All the GPIO pins can be reconfigured to provide alternate functions, SPI, [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM], I²C and so. At reset only pins GPIO 14 & 15 are assigned to the alternate function UART, these two can be switched back to GPIO to provide a total of 17 GPIO pins<ref>http://www.raspberrypi.org/archives/384</ref>. Each of their functions and full details of how to access are detailed in the chipset datasheet <ref>http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf</ref>.
+
All the GPIO pins can be reconfigured to provide alternate functions, SPI, [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM], I²C and so. At reset only pins GPIO 14 & 15 are assigned to the alternate function UART, these two can be switched back to GPIO to provide a total of 17 GPIO pins<ref>[http://www.raspberrypi.org/archives/384 raspberrypi.org]</ref>. Each of their functions and full details of how to access are detailed in the chipset datasheet <ref>[http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf raspberrypi.org]</ref>.
  
Each GPIO can interrupt, high/low/rise/fall/change.<ref>http://www.raspberrypi.org/archives/384#comment-5217</ref><ref>http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf</ref> There is currently no support for GPIO interrupts in the official kernel, howewer a patch exists, requiring compilation of modified source tree.<ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=7509</ref> The 'Raspbian "wheezy"' <ref>http://www.raspberrypi.org/downloads</ref> version that is currently recommended for starters already includes GPIO interrupts.
+
Each GPIO can interrupt, high/low/rise/fall/change.<ref>http://www.raspberrypi.org/archives/384#comment-5217</ref><ref>http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf</ref> There is currently no support for GPIO interrupts in the official kernel, however a patch exists, requiring compilation of modified source tree.<ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=7509</ref> The 'Raspbian "wheezy"' <ref>http://www.raspberrypi.org/downloads</ref> version that is currently recommended for starters already includes GPIO interrupts.
  
 
GPIO input hysteresis (Schmitt trigger) can be on or off, output slew rate can be fast or limited, and source and sink current is configurable from 2&nbsp;mA up to 16&nbsp;mA. Note that chipset GPIO pins 0-27 are in the same block and these properties are set per block, not per pin. See [http://www.scribd.com/doc/101830961/GPIO-Pads-Control2 GPIO Datasheet Addendum - GPIO Pads Control]. Particular attention should be applied to the note regarding SSO (Simultaneous Switching Outputs): to avoid interference, driving currents should be kept as low as possible.
 
GPIO input hysteresis (Schmitt trigger) can be on or off, output slew rate can be fast or limited, and source and sink current is configurable from 2&nbsp;mA up to 16&nbsp;mA. Note that chipset GPIO pins 0-27 are in the same block and these properties are set per block, not per pin. See [http://www.scribd.com/doc/101830961/GPIO-Pads-Control2 GPIO Datasheet Addendum - GPIO Pads Control]. Particular attention should be applied to the note regarding SSO (Simultaneous Switching Outputs): to avoid interference, driving currents should be kept as low as possible.
  
The available [[RPi_BCM2835_GPIOs|alternative functions]] and their corresponding pins are detailed below. These numbers are in reference to the chipset documentation and may not match the numbers exposed in Linux. Only fully usable functions are detailed, for some alternative functions not all the necessary pins are available for the funtionality to be actually used.
+
The available [[RPi BCM2835 GPIOs|alternative functions]] and their corresponding pins are detailed below. These numbers are in reference to the chipset documentation and may not match the numbers exposed in Linux. Only fully usable functions are detailed, for some alternative functions not all the necessary pins are available for the funtionality to be actually used.
  
 
There is also some information on the [[RPi Tutorial Easy GPIO Hardware & Software|Tutorial on Easy GPIO Hardware & Software]].
 
There is also some information on the [[RPi Tutorial Easy GPIO Hardware & Software|Tutorial on Easy GPIO Hardware & Software]].
  
Kernel boot messages go to the [[RPi_Serial_Connection|UART]] at 115200&nbsp;bit/s.
+
Kernel boot messages go to the UART at 115200&nbsp;bit/s - there are more details on the [[RPi Serial Connection|serial port]] page.
  
'''R-Pi PCB Revision 2 UPDATE:''' According to Eben at [http://www.raspberrypi.org/archives/1929#comment-31646] the R-Pi Rev.2 board being rolled out starting in September 2012 adds 4 more GPIO on a new connector called P5, and changes some of the existing P1 GPIO pinouts. On Rev2, GPIO_GEN2 [BCM2835/GPIO27] is routed to P1 pin 13, and changes what was SCL0/SDA0 to SCL1/SDA1: SCL1 [BCM2835/GPIO3] is routed to P1 pin 5, SDA1 [BCM2835/GPIO2] is routed to P1 pin 3. Also the power and ground connections previously marked "Do Not Connect" on P1 will remain as connected, specifically: P1-04:+5V0, P1-09:GND, P1-14:GND, P1-17:+3V3, P1-20:GND, P1-25:GND. According to this comment [http://www.raspberrypi.org/archives/2081#comment-33577] (and confirmed in this post [http://www.raspberrypi.org/archives/2233]) the P1 pinout is not expected to change in future beyond the current Rev.2 layout.
 
  
'''Header Pinout, top row:'''
+
 
 +
===P1 Header pinout, top row===
 
{| border="1" style="text-align:center;"
 
{| border="1" style="text-align:center;"
 
| '''Pin Number''' || '''Pin Name Rev1''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 
| '''Pin Number''' || '''Pin Name Rev1''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 
|-
 
|-
| P1-02 || bgcolor="red" | <span style="color:white">5V0</span> || bgcolor="red" | <span style="color:white">5V0</span> || Supply through input poly fuse
+
| P1-02 || bgcolor="red"  colspan="2" | <span style="color:white">5V0</span> || Supply through input poly fuse
|-
+
| &nbsp;
| P1-04 || bgcolor="red" | <span style="color:white">5V0</span> ||  bgcolor="red" | <span style="color:white">5V0</span> || Supply through input poly fuse
+
| &nbsp;
 
|-
 
|-
| P1-06 || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="black" | <span style="color:white">GND</span>
+
| P1-04 || bgcolor="red"  colspan="2" | <span style="color:white">5V0</span> || Supply through input poly fuse
 +
| &nbsp;
 +
| &nbsp;
 
|-
 
|-
 +
| P1-06 || bgcolor="black"  colspan="2" | <span style="color:white">GND</span>
 +
| &nbsp;
 +
| &nbsp;
 +
| &nbsp;
 
|-
 
|-
| P1-08 || bgcolor="lime" | GPIO 14 || bgcolor="lime" | GPIO 14 || Boot to Alt 0 -> || bgcolor="yellow" | UART0_TXD || ALT5 = UART1_TXD
+
| P1-08 || bgcolor="lime" colspan="2" | GPIO 14 || Boot to Alt 0 -> || bgcolor="yellow" | UART0_TXD || ALT5 = UART1_TXD
 
|-
 
|-
| P1-10 || bgcolor="lime" | GPIO 15 ||bgcolor="lime" | GPIO 15 || Boot to Alt 0 -> ||bgcolor="yellow" | UART0_RXD || ALT5 = UART1_RXD
+
| P1-10 || bgcolor="lime" colspan="2" | GPIO 15 || Boot to Alt 0 -> || bgcolor="yellow" | UART0_RXD || ALT5 = UART1_RXD
 
|-
 
|-
| P1-12 || bgcolor="lime" | GPIO 18 ||bgcolor="lime" | GPIO 18 || || || ALT4 SPI1_CE0_N ALT5 = PWM0
+
| P1-12 || bgcolor="lime" colspan="2" | GPIO 18 ||&nbsp; || PCM_CLK || ALT4 = SPI1_CE0_N ALT5 = PWM0
 
|-
 
|-
| P1-14 || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="black" | <span style="color:white">GND</span>
+
| P1-14 || bgcolor="black"  colspan="2" | <span style="color:white">GND</span>
 +
| &nbsp;
 +
| &nbsp;
 +
| &nbsp; 
 
|-
 
|-
| P1-16 || bgcolor="lime" | GPIO23 ||bgcolor="lime" | GPIO23 || || || ALT3 = SD1_CMD ALT4 = ARM_RTCK
+
| P1-16 || bgcolor="lime" colspan="2" | GPIO23 || || || ALT3 = SD1_CMD ALT4 = ARM_RTCK
 
|-
 
|-
| P1-18 || bgcolor="lime" | GPIO24 ||bgcolor="lime" | GPIO24 || || || ALT3 = SD1_DATA0 ALT4 = ARM_TDO
+
| P1-18 || bgcolor="lime" colspan="2" | GPIO24 || || || ALT3 = SD1_DAT0 ALT4 = ARM_TDO
 
|-
 
|-
| P1-20 || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="black" | <span style="color:white">GND</span>
+
| P1-20 || bgcolor="black"  colspan="2" | <span style="color:white">GND</span>  
 +
| &nbsp;
 +
| &nbsp;
 +
| &nbsp;
 
|-
 
|-
| P1-22 || bgcolor="lime" | GPIO25 ||bgcolor="lime" | GPIO25 || || || ALT4 = ARM_TCK
+
| P1-22 || bgcolor="lime" colspan="2" | GPIO25 || || || ALT3 = SD1_DAT1 ALT4 = ARM_TCK
 
|-
 
|-
| P1-24 || bgcolor="lime" | GPIO08 ||bgcolor="lime" | GPIO08 || || bgcolor="purple" | <span style="color:white">SPI0_CE0_N</span> ||
+
| P1-24 || bgcolor="lime" colspan="2" | GPIO08 || || bgcolor="purple" | <span style="color:white">SPI0_CE0_N</span> ||
 
|-
 
|-
| P1-26 || bgcolor="lime" | GPIO07 ||bgcolor="lime" | GPIO07 || || bgcolor="purple" | <span style="color:white">SPI0_CE1_N</span> ||  
+
| P1-26 || bgcolor="lime" colspan="2" | GPIO07 || || bgcolor="purple" | <span style="color:white">SPI0_CE1_N</span> ||  
 
|}
 
|}
  
 
+
===P1 Header pinout, bottom row===
'''Header Pinout, bottom row:'''
+
 
{| border="1" style="text-align:center;"
 
{| border="1" style="text-align:center;"
 
| '''Pin Number''' || '''Pin Name Rev1''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 
| '''Pin Number''' || '''Pin Name Rev1''' || '''Pin Name Rev2''' || '''Hardware Notes''' || '''Alt 0 Function''' || '''Other Alternative Functions'''
 
|-
 
|-
| P1-01 || bgcolor="orange" | 3.3&nbsp;V ||bgcolor="orange" | 3.3&nbsp;V || 50&nbsp;mA max (01 & 17)
+
| P1-01 || bgcolor="orange" colspan="2" | 3.3&nbsp;V || 50&nbsp;mA max (01 & 17)
 +
| &nbsp;
 +
| &nbsp;
 
|-
 
|-
| P1-03 || bgcolor="lime" | GPIO 0 ||bgcolor="lime" | '''GPIO 2'''|| 1K8 pull up resistor || bgcolor="cyan" | I2C0_SDA ||  I2C0_SDA / I2C1_SDA
+
| P1-03 || bgcolor="lime" | GPIO 0 || bgcolor="lime" | '''GPIO 2'''|| 1K8 pull up resistor || bgcolor="cyan" | I2C0_SDA / '''I2C1_SDA''' ||
 
|-
 
|-
| P1-05 || bgcolor="lime" | GPIO 1 ||bgcolor="lime" | '''GPIO 3'''|| 1K8 pull up resistor || bgcolor="cyan" | I2C0_SCL ||  I2C0_SCL / I2C1_SCL  
+
| P1-05 || bgcolor="lime" | GPIO 1 || bgcolor="lime" | '''GPIO 3'''|| 1K8 pull up resistor || bgcolor="cyan" | I2C0_SCL / '''I2C1_SCL''' ||
 
|-
 
|-
| P1-07 || bgcolor="lime" | GPIO 4 ||bgcolor="lime" | GPIO 4 || || || bgcolor="lime" | GPCLK0
+
| P1-07 || bgcolor="lime" colspan="2" | GPIO 4 || || GPCLK0 || ALT5 = ARM_TDI
 
|-
 
|-
| P1-09 || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="black" | <span style="color:white">GND</span>
+
| P1-09 || bgcolor="black"  colspan="2" | <span style="color:white">GND</span>
 +
| &nbsp;
 +
| &nbsp;
 +
| &nbsp; 
 
|-
 
|-
| P1-11 || bgcolor="lime" | GPIO17 || bgcolor="lime" | GPIO17 || || ||| ALT3 = UART0_RTS, ALT5 = UART1_RTS
+
| P1-11 || bgcolor="lime" colspan="2" | GPIO17 || || ||| ALT3 = UART0_RTS ALT4 = SPI1_CE1_N ALT5 = UART1_RTS
 
|-
 
|-
| P1-13 || bgcolor="lime" | GPIO21 || bgcolor="lime" | '''GPIO27''' || || PCM_DIN || ALT5 = GPCLK1
+
| P1-13 || bgcolor="lime" | GPIO21 || bgcolor="lime" | '''GPIO27''' || || PCM_DOUT / '''reserved''' || ALT4 = SPI1_SCLK ALT5 = GPCLK1 / '''ALT3 = SD1_DAT3 ALT4 = ARM_TMS'''
 
|-
 
|-
| P1-15 || bgcolor="lime" | GPIO22 || bgcolor="lime" | GPIO22 || || || ALT3 = SD1_CLK ALT4 = ARM_TRST
+
| P1-15 || bgcolor="lime" colspan="2" | GPIO22 || || || ALT3 = SD1_CLK ALT4 = ARM_TRST
 
|-
 
|-
| P1-17 || bgcolor="orange" | 3.3&nbsp;V ||bgcolor="orange" | 3.3&nbsp;V || 50&nbsp;mA max (01 & 17)
+
| P1-17 || bgcolor="orange" colspan="2" | 3.3&nbsp;V || 50&nbsp;mA max (01 & 17)
 +
| &nbsp;
 +
| &nbsp;
 
|-
 
|-
| P1-19 || bgcolor="lime" | GPIO10 || bgcolor="lime" | GPIO10 || || bgcolor="purple" | <span style="color:white">SPI0_MOSI</span> ||  
+
| P1-19 || bgcolor="lime"  colspan="2" | GPIO10 || || bgcolor="purple" | <span style="color:white">SPI0_MOSI</span> ||  
 
|-
 
|-
| P1-21 || bgcolor="lime" | GPIO9 || bgcolor="lime" | GPIO9 || || bgcolor="purple" | <span style="color:white">SPI0_MISO</span> ||
+
| P1-21 || bgcolor="lime" colspan="2" | GPIO9 || || bgcolor="purple" | <span style="color:white">SPI0_MISO</span> ||
 
|-
 
|-
| P1-23 || bgcolor="lime" | GPIO11 || bgcolor="lime" | GPIO11 || || bgcolor="purple" | <span style="color:white">SPI0_SCLK</span> ||  
+
| P1-23 || bgcolor="lime" colspan="2" | GPIO11 || || bgcolor="purple" | <span style="color:white">SPI0_SCLK</span> ||  
 
|-
 
|-
| P1-25 || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="black" | <span style="color:white">GND</span>
+
| P1-25 || bgcolor="black"  colspan="2" | <span style="color:white">GND</span>  
 +
| &nbsp;
 +
| &nbsp;
 +
| &nbsp;
 
|}
 
|}
  
Line 116: Line 247:
 
|}
 
|}
  
KiCad symbol: [[File:Conn-raspberry.lib]]
+
KiCad symbol: [[File:Conn-raspberry.lib]]<ref>http://www.raspberrypi.org/forum/projects-and-collaboration-general/gpio-header-pinout-clarification/page-2</ref>
  
<ref>http://www.raspberrypi.org/forum/projects-and-collaboration-general/gpio-header-pinout-clarification/page-2</ref>
+
Pin 3 (SDA0) and Pin 5 (SCL0) are preset to be used as an I²C interface. So there are 1.8&nbsp;kohm pulls up resistors on the board for these pins.<ref>http://www.raspberrypi.org/forum/features-and-requests/easy-gpio-hardware-software/page-6/#p56480</ref>
  
Pin 3 (SDA0) and Pin 5 (SCL0) are preset to be used as an I²C interface. So there are 1.8&nbsp;kilohm pulls up resistors on the board for these pins.<ref>http://www.raspberrypi.org/forum/features-and-requests/easy-gpio-hardware-software/page-6/#p56480</ref>
+
Pin 12 supports [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM].
  
Pin 12 supports [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM] .
+
It is also possible to reconfigure GPIO connector pins P1-7, 15, 16, 18, 22 (chipset GPIOs 4 and 22 to 25) to provide an ARM JTAG interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.1</ref> However ARM_TMS is not available on the GPIO connector (chipset pin 12 or 27 is needed). Chipset pin 27 is available on S5, the CSI camera interface however.
 
+
It is also possible to reconfigure GPIO connector pins P1-7, 15, 16, 18, 22 (chipset GPIOs 4 and 22 to 25) to provide an ARM JTAG interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.1</ref> However ARM_TMS isn't available on the GPIO connector (chipset pin 12 or 27 is needed). Chipset pin 27 is available on S5, the CSI camera interface however.
+
  
 
It is also possible to reconfigure GPIO connector pins P1-12 and 13 (chipset GPIO 18 and 21) to provide an I2S (a hardware modification may be required<ref name="I2S">[http://www.raspberrypi.org/forum/features-and-requests/sad-about-removal-of-i2s-why-was-this-change-made Forum:Sad about removal of I2S. Why was this change made?]</ref>) or PCM interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.2</ref> However, PCM_FS and PCM_DIN (chipset pins 19 and 20) are needed for I2S or PCM.
 
It is also possible to reconfigure GPIO connector pins P1-12 and 13 (chipset GPIO 18 and 21) to provide an I2S (a hardware modification may be required<ref name="I2S">[http://www.raspberrypi.org/forum/features-and-requests/sad-about-removal-of-i2s-why-was-this-change-made Forum:Sad about removal of I2S. Why was this change made?]</ref>) or PCM interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.2</ref> However, PCM_FS and PCM_DIN (chipset pins 19 and 20) are needed for I2S or PCM.
Line 131: Line 260:
  
 
===Referring to pins on the Expansion header===
 
===Referring to pins on the Expansion header===
 
+
The header is referred to as "The GPIO Connector (P1)".  To avoid nomenclature confusion between Broadcom signal names on the SoC and pin names on the expansion header, the following naming is highly recommended:
The header is referred to as "The GPIO Connector (P1)".  To avoid nomenclature confusion between Broadcom signal names on the SoC and pin names on the expansion header, the following naming is highly recommended.
+
 
+
 
* The expansion header is referred to as "Expansion Header" or "GPIO Connector (P1)"
 
* The expansion header is referred to as "Expansion Header" or "GPIO Connector (P1)"
 
* Pins on the GPIO connector (P1) are referred to as P1-01, etc.
 
* Pins on the GPIO connector (P1) are referred to as P1-01, etc.
 
* Names GPIO0, GPIO1, GPIOx-ALTy, etc. refer to the signal names on the SoC as enumerated in the Broadcom datasheet, where "x" matches BCM2835 number (without leading zero) and "y" is the alternate number column 0 to 5 on page 102-103 of the Broadcom document. For example, depending on what you are describing, use either "GPIO7" to refer to a row of the table, and "GPIO7-ALT0" would refer to a specific cell of the table.
 
* Names GPIO0, GPIO1, GPIOx-ALTy, etc. refer to the signal names on the SoC as enumerated in the Broadcom datasheet, where "x" matches BCM2835 number (without leading zero) and "y" is the alternate number column 0 to 5 on page 102-103 of the Broadcom document. For example, depending on what you are describing, use either "GPIO7" to refer to a row of the table, and "GPIO7-ALT0" would refer to a specific cell of the table.
* When refering to signal names, you should modify the Broadcom name slightly to minimize confusion. The Broadcom SPI bus pin names are fine, such as "SPI0_*" and "SPI1_*", but they didn't do the same on the I²C and UART pins. Instead of using "SDA0" and "SCL0", you should use "I2C0_SDA" and "I2C0_SCL"; and instead of "TX" or "TXD" and "RX" or "RXD", you should use "UART0_TXD" and "UART0_RXD".
+
* When refering to signal names, the Broadcom name should be modified slightly to minimize confusion. The Broadcom SPI bus pin names are fine, such as "SPI0_*" and "SPI1_*", but they did not do the same on the I²C and UART pins. Instead of using "SDA0" and "SCL0", "I2C0_SDA" and "I2C0_SCL" should be used; and "UART0_TXD" and "UART0_RXD" instead of "TX" or "TXD" and "RX" or "RXD".
  
 
===Power pins===
 
===Power pins===
Line 145: Line 272:
 
*Model A: 1000&nbsp;mA - 500&nbsp;mA -> max current draw: 500&nbsp;mA
 
*Model A: 1000&nbsp;mA - 500&nbsp;mA -> max current draw: 500&nbsp;mA
 
*Model B: 1000&nbsp;mA - 700&nbsp;mA -> max current draw: 300&nbsp;mA
 
*Model B: 1000&nbsp;mA - 700&nbsp;mA -> max current draw: 300&nbsp;mA
Be very careful with the 5&nbsp;V pins P1-02 and P1-04, because if you short 5&nbsp;V to any other P1 pin you may permanently damage your RasPi. Before probing P1, it's a good idea to strip short pieces of insulation off a wire and push them over the 5&nbsp;V pins so you don't accidentally short them with a probe.
+
Be very careful with the 5&nbsp;V pins P1-02 and P1-04, because if you short 5&nbsp;V to any other P1 pin you may permanently damage your RasPi. Before probing P1, it is a good idea to strip short pieces of insulation off a wire and push them over the 5&nbsp;V pins are not accidentally shorted with a probe.
  
 
=== GPIO hardware hacking ===
 
=== GPIO hardware hacking ===
 
 
The complete list of [[RPi_BCM2835_GPIOs|chipset GPIO pins]] which are available on the GPIO connector is: <blockquote>[[RPi_BCM2835_GPIOs#GPIO0|0]], [[RPi_BCM2835_GPIOs#GPIO1|1]], [[RPi_BCM2835_GPIOs#GPIO4|4]], [[RPi_BCM2835_GPIOs#GPIO7|7]], [[RPi_BCM2835_GPIOs#GPIO8|8]], [[RPi_BCM2835_GPIOs#GPIO9|9]], [[RPi_BCM2835_GPIOs#GPIO10|10]], [[RPi_BCM2835_GPIOs#GPIO11|11]], [[RPi_BCM2835_GPIOs#GPIO14|14]], [[RPi_BCM2835_GPIOs#GPIO15|15]], [[RPi_BCM2835_GPIOs#GPIO17|17]], [[RPi_BCM2835_GPIOs#GPIO18|18]], [[RPi_BCM2835_GPIOs#GPIO21|21]], [[RPi_BCM2835_GPIOs#GPIO22|22]], [[RPi_BCM2835_GPIOs#GPIO23|23]], [[RPi_BCM2835_GPIOs#GPIO24|24]], [[RPi_BCM2835_GPIOs#GPIO25|25]]</blockquote>
 
The complete list of [[RPi_BCM2835_GPIOs|chipset GPIO pins]] which are available on the GPIO connector is: <blockquote>[[RPi_BCM2835_GPIOs#GPIO0|0]], [[RPi_BCM2835_GPIOs#GPIO1|1]], [[RPi_BCM2835_GPIOs#GPIO4|4]], [[RPi_BCM2835_GPIOs#GPIO7|7]], [[RPi_BCM2835_GPIOs#GPIO8|8]], [[RPi_BCM2835_GPIOs#GPIO9|9]], [[RPi_BCM2835_GPIOs#GPIO10|10]], [[RPi_BCM2835_GPIOs#GPIO11|11]], [[RPi_BCM2835_GPIOs#GPIO14|14]], [[RPi_BCM2835_GPIOs#GPIO15|15]], [[RPi_BCM2835_GPIOs#GPIO17|17]], [[RPi_BCM2835_GPIOs#GPIO18|18]], [[RPi_BCM2835_GPIOs#GPIO21|21]], [[RPi_BCM2835_GPIOs#GPIO22|22]], [[RPi_BCM2835_GPIOs#GPIO23|23]], [[RPi_BCM2835_GPIOs#GPIO24|24]], [[RPi_BCM2835_GPIOs#GPIO25|25]]</blockquote>
  
(on the Revision2.0 RaspberryPis, this list changes to: [[RPi_BCM2835_GPIOs#GPIO2|2]], [[RPi_BCM2835_GPIOs#GPIO3|3]], [[RPi_BCM2835_GPIOs#GPIO4|4]], [[RPi_BCM2835_GPIOs#GPIO7|7]], [[RPi_BCM2835_GPIOs#GPIO8|8]], [[RPi_BCM2835_GPIOs#GPIO9|9]], [[RPi_BCM2835_GPIOs#GPIO10|10]], [[RPi_BCM2835_GPIOs#GPIO11|11]], [[RPi_BCM2835_GPIOs#GPIO14|14]], [[RPi_BCM2835_GPIOs#GPIO15|15]], [[RPi_BCM2835_GPIOs#GPIO17|17]], [[RPi_BCM2835_GPIOs#GPIO18|18]], [[RPi_BCM2835_GPIOs#GPIO22|22]], [[RPi_BCM2835_GPIOs#GPIO23|23]], [[RPi_BCM2835_GPIOs#GPIO24|24]], [[RPi_BCM2835_GPIOs#GPIO25|25]], [[RPi_BCM2835_GPIOs#GPIO27|27]])
+
(on the Revision2.0 RaspberryPis, this list changes to: [[RPi_BCM2835_GPIOs#GPIO2|2]], [[RPi_BCM2835_GPIOs#GPIO3|3]], [[RPi_BCM2835_GPIOs#GPIO4|4]], [[RPi_BCM2835_GPIOs#GPIO7|7]], [[RPi_BCM2835_GPIOs#GPIO8|8]], [[RPi_BCM2835_GPIOs#GPIO9|9]], [[RPi_BCM2835_GPIOs#GPIO10|10]], [[RPi_BCM2835_GPIOs#GPIO11|11]], [[RPi_BCM2835_GPIOs#GPIO14|14]], [[RPi_BCM2835_GPIOs#GPIO15|15]], [[RPi_BCM2835_GPIOs#GPIO17|17]], [[RPi_BCM2835_GPIOs#GPIO18|18]], [[RPi_BCM2835_GPIOs#GPIO22|22]], [[RPi_BCM2835_GPIOs#GPIO23|23]], [[RPi_BCM2835_GPIOs#GPIO24|24]], [[RPi_BCM2835_GPIOs#GPIO25|25]], [[RPi_BCM2835_GPIOs#GPIO27|27]], with [[RPi_BCM2835_GPIOs#GPIO28|28]], [[RPi_BCM2835_GPIOs#GPIO29|29]], [[RPi_BCM2835_GPIOs#GPIO30|30]], [[RPi_BCM2835_GPIOs#GPIO31|31]] additionally available on the [[#P5_header|P5 header]])
  
As noted above, GPIO00 and 01 (SDA0 and SCL0) have 1.8&nbsp;kilohm pull-up resistors to 3.3&nbsp;V.
+
As noted above, P1-03 and P1-05 (SDA0 and SCL0 / SDA1 and SCL1) have 1.8&nbsp;kohm pull-up resistors to 3.3&nbsp;V.
  
If 17 GPIOs aren't sufficient for your project, there are a few other signals potentially available, with varying levels of software and hardware (soldering iron) hackery skills:
+
If 17 GPIOs are not sufficient for a project, there are a few other signals potentially available, with varying levels of software and hardware (soldering iron) hackery skills:
  
 
GPIO02, 03, 05 and 27 are available on S5 (the CSI interface) when a camera peripheral is not connected to that socket, and are configured by default to provide the functions SDA1, SCL1, CAM_CLK and CAM_GPIO respectively.  SDA1 and SCL1 have 1K6 pull-up resistors to 3.3&nbsp;V.
 
GPIO02, 03, 05 and 27 are available on S5 (the CSI interface) when a camera peripheral is not connected to that socket, and are configured by default to provide the functions SDA1, SCL1, CAM_CLK and CAM_GPIO respectively.  SDA1 and SCL1 have 1K6 pull-up resistors to 3.3&nbsp;V.
Line 162: Line 288:
  
 
There are a few other chipset GPIO pins accessible on the PCB but are in use:
 
There are a few other chipset GPIO pins accessible on the PCB but are in use:
 
 
* GPIO16 drives status LED D5 (usually SD card access indicator)
 
* GPIO16 drives status LED D5 (usually SD card access indicator)
* GPIO28-31 are used by the board ID and are connected to resistors R3 to R10.
+
* GPIO28-31 are used by the board ID and are connected to resistors R3 to R10 (only on Rev1.0 boards).
 
* GPIO40 and 45 are used by analogue audio and support [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM]. They connect to the analogue audio circuitry via R21 and R27 respectively.
 
* GPIO40 and 45 are used by analogue audio and support [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM]. They connect to the analogue audio circuitry via R21 and R27 respectively.
 
* GPIO46 is HDMI hotplug detect (goes to pin 6 of IC1).
 
* GPIO46 is HDMI hotplug detect (goes to pin 6 of IC1).
 
* GPIO47 to 53 are used by the SD card interface.  In particular, GPIO47 is SD card detect (this would seem to be a good candidate for re-use).  GPIO47 is connected to the SD card interface card detect switch; GPIO48 to 53 are connected to the SD card interface via resistors R45 to R50.
 
* GPIO47 to 53 are used by the SD card interface.  In particular, GPIO47 is SD card detect (this would seem to be a good candidate for re-use).  GPIO47 is connected to the SD card interface card detect switch; GPIO48 to 53 are connected to the SD card interface via resistors R45 to R50.
  
=== P2 header ===
 
  
The P2 header is the VideoCore JTAG and used only during the production of the board. It cannot be used as the ARM JTAG <ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894</ref>. This connector is unpopulated in Rev 2.0 boards.
+
===Internal Pull-Ups & Pull-Downs===
 
+
The GPIO ports include the ability to enable and disable internal pull-up or pull-down resistors (see below for code examples/support of this):
Useful P2 pins:
+
* Pull-up is 50 kOhm - 65 kOhm
 
+
* Pull-down is 50 kOhm - 60 kOhm
* Pin 1 - 3.3V (same as P1-01, 50 mA max current draw across both of them)
+
* Pin 7 - GND
+
* Pin 8 - GND
+
 
+
=== P3 header ===
+
 
+
The P3 header, unpopulated, is the LAN9512 JTAG <ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894</ref>.
+
 
+
=== P5 header ===
+
 
+
The P5 header was added with the release of the Revision 2.0 PCB design.
+
 
+
* Pin 1 - 5V
+
* Pin 2 - 3V3
+
* Pin 3 - GPIO28
+
* Pin 4 - GPIO29
+
* Pin 5 - GPIO30
+
* Pin 6 - GPIO31
+
* Pin 7 - GND
+
* Pin 8 - GND
+
 
+
Note that the connector is intended to be mounted on the bottom of the PCB, so that for those who put the connector on the top side, the pin numbers are swapped. Pin 1 and pin 2 are  swapped, pin 3 and 4, etc.
+
 
+
Note that the connector is placed JUST off-grid with respect to the P1 connector.
+
 
+
=== P6 header ===
+
 
+
The P6 header was added with the release of the Revision 2.0 PCB design.
+
 
+
The P6 header can be used to connect a reset button to, which with the PI can be reset.
+
  
 
===Driver support===
 
===Driver support===
 
 
The Foundation will not include a GPIO driver in the initial release, standard Linux GPIO drivers should work with minimal modification.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1278.0</ref>
 
The Foundation will not include a GPIO driver in the initial release, standard Linux GPIO drivers should work with minimal modification.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1278.0</ref>
  
The community implemented SPI and I²C drivers <ref>http://www.bootc.net/projects/raspberry-pi-kernel/</ref>, which will be integrated with the new Linux pinctrl concept in a later version of the kernel. (On Oct.14,it was already included in the latest raspbian image.)A first compiled version as Linux modules is available to install on the 19/04/2012 Debian image, including 1-wire support<ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?p=86172#p86172</ref>. The I²C and SPI driver uses the hardware modules of the microcontroller and interrupts for low CPU usage, the 1-wire support uses bitbanging on the GPIO ports, which results in higher CPU usage.
+
The community implemented SPI and I²C drivers <ref>http://www.bootc.net/projects/raspberry-pi-kernel/</ref>, which will be integrated with the new Linux pinctrl concept in a later version of the kernel. (On Oct. 14 2012, it was already included in the latest raspbian image.) A first compiled version as Linux modules is available to install on the 19/04/2012 Debian image, including 1-wire support<ref>http://www.raspberrypi.org/phpBB3/viewtopic.php?p=86172#p86172</ref>. The I²C and SPI driver uses the hardware modules of the microcontroller and interrupts for low CPU usage, the 1-wire support uses bitbanging on the GPIO ports, which results in higher CPU usage.
  
 
GordonH<ref>http://www.raspberrypi.org/forum/general-discussion/wiring-for-the-raspberry-pis-gpio</ref> wrote a (mostly) Arduino compatible/style [https://projects.drogon.net/raspberry-pi/wiringpi/ WiringPi library] in C for controlling the GPIO pins.
 
GordonH<ref>http://www.raspberrypi.org/forum/general-discussion/wiring-for-the-raspberry-pis-gpio</ref> wrote a (mostly) Arduino compatible/style [https://projects.drogon.net/raspberry-pi/wiringpi/ WiringPi library] in C for controlling the GPIO pins.
Line 216: Line 309:
 
A useful tutorial on setting up I²C driver support can be found at [http://www.robot-electronics.co.uk/htm/raspberry_pi_examples.htm Robot Electronics] - look for the downloadable document rpi_i2c_setup.doc
 
A useful tutorial on setting up I²C driver support can be found at [http://www.robot-electronics.co.uk/htm/raspberry_pi_examples.htm Robot Electronics] - look for the downloadable document rpi_i2c_setup.doc
  
===Graphical User Interfaces===
+
==SPI==
====WebIOPi====
+
[http://code.google.com/p/webiopi/ WebIOPi] allows you to control each GPIO with a simple web interface that you can use with any browser. Available in PHP and Python, they both require root access, but Python version serves HTTP itself. You can setup each GPIO as input or output and change their states (LOW/HIGH). WebIOPi is fully customizable, so you can use it for home remote control. It also work over Internet. UART/SPI/I2C support will be added later. If you need some computing for your GPIO go to code examples below.
+
  
==GPIO Code examples==
+
There is one SPI bus brought out to the header: [[RPi_SPI]]
====GPIO Driving Example (C)====
+
[http://www.raspberrypi.org/forum/educational-applications/gertboard/page-4/#p31555 Gert van Loo & Dom, has provided] some tested code which accesses the GPIO pins through direct GPIO register manipulation in C-code.
+
(Thanks to Dom for doing the difficult work of finding and testing the mapping.)
+
Example GPIO code:
+
  
<pre>
+
==I²C==
//
+
//  How to access GPIO registers from C-code on the Raspberry-Pi
+
//  Example program
+
//  15-January-2012
+
//  Dom and Gert
+
//
+
  
 +
There are two I²C-buses on the Raspberry Pi: One on P1, and one on P5.
  
// Access from ARM Running Linux
+
Note that there's a bug concerning I²C-clock-stretching, so don't use I²C-devices which use clock-stretching directly with the Raspberry Pi, or use a workaround. Details about this bug can be found at:
  
#define BCM2708_PERI_BASE        0x20000000
+
* http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=13771
#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
+
* http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
 
+
 
+
#include <stdio.h>
+
#include <string.h>
+
#include <stdlib.h>
+
#include <dirent.h>
+
#include <fcntl.h>
+
#include <assert.h>
+
#include <sys/mman.h>
+
#include <sys/types.h>
+
#include <sys/stat.h>
+
 
+
#include <unistd.h>
+
 
+
#define PAGE_SIZE (4*1024)
+
#define BLOCK_SIZE (4*1024)
+
 
+
int  mem_fd;
+
char *gpio_mem, *gpio_map;
+
char *spi0_mem, *spi0_map;
+
 
+
 
+
// I/O access
+
volatile unsigned *gpio;
+
 
+
 
+
// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
+
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
+
#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
+
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
+
 
+
#define GPIO_SET *(gpio+7)  // sets  bits which are 1 ignores bits which are 0
+
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
+
 
+
void setup_io();
+
 
+
int main(int argc, char **argv)
+
{
+
  int g,rep;
+
 
+
  // Set up gpi pointer for direct register access
+
  setup_io();
+
 
+
  // Switch GPIO 7..11 to output mode
+
 
+
/************************************************************************\
+
  * You are about to change the GPIO settings of your computer.          *
+
  * Mess this up and it will stop working!                              *
+
  * It might be a good idea to 'sync' before running this program        *
+
  * so at least you still have your code changes written to the SD-card! *
+
\************************************************************************/
+
 
+
  // Set GPIO pins 7-11 to output
+
  for (g=7; g<=11; g++)
+
  {
+
    INP_GPIO(g); // must use INP_GPIO before we can use OUT_GPIO
+
    OUT_GPIO(g);
+
  }
+
 
+
  for (rep=0; rep<10; rep++)
+
  {
+
    for (g=7; g<=11; g++)
+
    {
+
      GPIO_SET = 1<<g;
+
      sleep(1);
+
    }
+
    for (g=7; g<=11; g++)
+
    {
+
      GPIO_CLR = 1<<g;
+
      sleep(1);
+
    }
+
  }
+
 
+
  return 0;
+
 
+
} // main
+
 
+
 
+
//
+
// Set up a memory regions to access GPIO
+
//
+
void setup_io()
+
{
+
  /* open /dev/mem */
+
  if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
+
      printf("can't open /dev/mem \n");
+
      exit (-1);
+
  }
+
 
+
  /* mmap GPIO */
+
 
+
  // Allocate MAP block
+
  if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
+
      printf("allocation error \n");
+
      exit (-1);
+
  }
+
 
+
  // Make sure pointer is on 4K boundary
+
  if ((unsigned long)gpio_mem % PAGE_SIZE)
+
    gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
+
 
+
  // Now map it
+
  gpio_map = (unsigned char *)mmap(
+
      (caddr_t)gpio_mem,
+
      BLOCK_SIZE,
+
      PROT_READ|PROT_WRITE,
+
      MAP_SHARED|MAP_FIXED,
+
      mem_fd,
+
      GPIO_BASE
+
  );
+
 
+
  if ((long)gpio_map < 0) {
+
      printf("mmap error %d\n", (int)gpio_map);
+
      exit (-1);
+
  }
+
 
+
  // Always use volatile pointer!
+
  gpio = (volatile unsigned *)gpio_map;
+
 
+
 
+
} // setup_io
+
 
+
</pre>
+
 
+
====GPIO Pull Up/Pull Down Register Example====
+
<pre>
+
  // enable pull-up on GPIO24&25
+
  GPIO_PULL = 2;
+
  short_wait();
+
  // clock on GPIO 24 & 25 (bit 24 & 25 set)
+
  GPIO_PULLCLK0 = 0x03000000;
+
  short_wait();
+
  GPIO_PULL = 0;
+
  GPIO_PULLCLK0 = 0;
+
</pre>
+
 
+
====GPIO Driving Example (Python)====
+
This uses the Python module available at http://pypi.python.org/pypi/RPi.GPIO
+
Any Python script that controls GPIO must be run as root.
+
<pre>import RPi.GPIO as GPIO
+
 
+
# Set up the GPIO channels - one input and one output
+
GPIO.setup(11, GPIO.IN)
+
GPIO.setup(12, GPIO.OUT)
+
 
+
# Input from pin 11
+
input_value = GPIO.input(11)
+
 
+
# Output to pin 12
+
GPIO.output(12, True)
+
 
+
# The same script as above but using BCM GPIO 00..nn numbers
+
GPIO.setmode(GPIO.BCM)
+
GPIO.setup(17, GPIO.IN)
+
GPIO.setup(18, GPIO.OUT)
+
input_value = GPIO.input(17)
+
GPIO.output(18, True)</pre>
+
 
+
 
+
====GPIO Driving Example (Java using the Pi4J Library)====
+
This uses the Java library available at http://www.pi4j.com/.
+
(Any Java application that controls GPIO must be run as root.)
+
 
+
Please note that the Pi4J library uses the WiringPi GPIO pin numbering scheme <ref>http://pi4j.com/usage.html#Pin_Numbering</ref> <ref>https://projects.drogon.net/raspberry-pi/wiringpi/pins/</ref>.  Please see the usage documentation for more details: http://pi4j.com/usage.html 
+
 
+
<pre>
+
 
+
public static void main(String[] args) {
+
 
+
    // create gpio controller
+
    GpioController gpio = GpioFactory.getInstance();
+
       
+
    // provision gpio pin #01 as an output pin and turn off
+
    GpioPinDigitalOutput outputPin = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_01, "MyLED", PinState.LOW);
+
   
+
    // turn output to LOW/OFF state
+
    outputPin.low();
+
 
+
    // turn output to HIGH/ON state
+
    outputPin.high();
+
 
+
 
+
    // provision gpio pin #02 as an input pin with its internal pull down resistor enabled
+
    GpioPinDigitalInput inputPin = gpio.provisionDigitalInputPin(RaspiPin.GPIO_02, "MyButton", PinPullResistance.PULL_DOWN);
+
 
+
    // get input state from pin 2
+
    boolean input_value = inputPin.isHigh();
+
}
+
</pre>
+
 
+
More complete and detailed examples are included on the Pi4J website at http://www.pi4j.com/.
+
 
+
The Pi4J library includes support for:
+
* GPIO Control
+
* GPIO Listeners
+
* Serial Communication
+
* I2C Communication
+
* SPI Communication
+
 
+
====GPIO Driving Example (Java)====
+
This uses the Java library available at https://github.com/jkransen/framboos. It does not depend on (or use) the wiringPi driver, but uses the same numbering scheme. Instead it uses the default driver under /sys/class/gpio that ships with the distro, so it works out of the box. Any Java application that controls GPIO must be run as root.
+
<pre>
+
public static void main(String[] args) {
+
  // reading from an in pin
+
  InPin button = new InPin(8);
+
  boolean isButtonPressed = button.getValue();
+
  button.close();
+
 
+
  // writing to an out pin
+
  OutPin led = new Outpin(0);
+
  led.setValue(true);
+
  led.setValue(false);
+
  led.close();
+
}
+
</pre>
+
 
+
====GPIO Driving Example (Java Webapp GPIO web control via http)====
+
This uses the Java Webapp available at https://bitbucket.org/sbub/raspberry-pi-gpio-web-control/overview. You can control your GPIO over the internet. Any Java application that controls GPIO must be run as root.
+
<pre>
+
 
+
host:~ sb$ curl 'http://raspberrypi:8080/handle?g0=1&g1=0'
+
{"g1":0,"g0":1}
+
 
+
</pre>
+
 
+
====GPIO Driving Example (Bash shell script)====
+
The export and unexport of pins must be done as root.
+
To change to the root user see below:  To change back, the word exit must be entered.
+
<pre>sudo -i</pre>
+
Export creates a new folder for the exported pin, and creates files for each of its control functions. Upon creation, the control files can be read by all users (not just root), but can only be written to by user root, the file's owner. Nevertheless, once created, it is possible to allow users other than root, to also write inputs to the control files, by changing the ownership or permissions of these files. Changes to the file's ownership or permissions must initially be done as root, as their owner and group is set to root upon creation. Typically you might change the owner to be the (non root) user controlling the GPIO, or you might add write permission, and change the group ownership to one of which the user controlling the GPIO is a member. By such means, using only packages provided in the recommended rasbian distribution, it is possible for Python CGI scripts, which are typically run as user nobody, to be used for control of the GPIO over the internet from a browser at a remote location.
+
<pre>
+
#!/bin/sh
+
 
+
# GPIO numbers should be from this list
+
# 0, 1, 4, 7, 8, 9, 10, 11, 14, 15, 17, 18, 21, 22, 23, 24, 25
+
 
+
# Note that the GPIO numbers that you program here refer to the pins
+
# of the BCM2835 and *not* the numbers on the pin header.
+
# So, if you want to activate GPIO7 on the header you should be
+
# using GPIO4 in this script. Likewise if you want to activate GPIO0
+
# on the header you should be using GPIO17 here.
+
 
+
# Set up GPIO 4 and set to output
+
echo "4" > /sys/class/gpio/export
+
echo "out" > /sys/class/gpio/gpio4/direction
+
 
+
# Set up GPIO 7 and set to input
+
echo "7" > /sys/class/gpio/export
+
echo "in" > /sys/class/gpio/gpio7/direction
+
 
+
# Write output
+
echo "1" > /sys/class/gpio/gpio4/value
+
 
+
# Read from input
+
cat /sys/class/gpio/gpio7/value
+
 
+
# Clean up
+
echo "4" > /sys/class/gpio/unexport
+
echo "7" > /sys/class/gpio/unexport
+
</pre>
+
 
+
====GPIO Driving Example (Shell script - take 2)====
+
You need the wiringPi library from
+
https://projects.drogon.net/raspberry-pi/wiringpi/download-and-install/. Once installed, there is a new command '''gpio''' which can be used
+
as a '''non-root''' user to control the GPIO pins.
+
 
+
The man page <pre>man gpio</pre> has full details, but briefly:
+
 
+
<pre>
+
  gpio -g mode 17 out
+
  gpio -g mode 18 pwm
+
 
+
  gpio -g write 17 1
+
  gpio -g pwm 18 512
+
</pre>
+
 
+
The '''-g''' flag tells the '''gpio''' program to use the BCM GPIO pin numbering
+
scheme (otherwise it will use the wiringPi numbering scheme by default).
+
 
+
The gpio command can also control the internal pull-up and pull-down
+
resistors:
+
 
+
<pre>
+
  gpio -g mode 17 up
+
</pre>
+
 
+
This sets the pull-up resistor - however any change of mode, even
+
setting a pin that's already set as an input to an input will remove
+
the pull-up/pull-down resistors, so they may need to be reset.
+
 
+
Additionally, it can export/un-export the GPIO devices for use by
+
other non-root programms - e.g. Python scripts. (Although you
+
may need to drop the calls to GPIO.Setup() in the Python scripts, and
+
do the setup separately in a little shell script, or call the '''gpio''' program
+
from inside Python).
+
 
+
<pre>
+
  gpio export 17 out
+
  gpio export 18 in
+
</pre>
+
 
+
These exports GPIO-17 and sets it to output, and exports GPIO-18
+
and sets it to input.
+
 
+
And when done:
+
 
+
<pre>
+
  gpio unexport 17
+
</pre>
+
 
+
The export/unexport commands always use the BCM GPIO pin numbers regardless of the
+
presence of the '''-g''' flag or not.
+
 
+
If you want to use the internal pull-up/down's with the /sys/class/gpio mechanisms,
+
then you can set them after exporting them. So:
+
 
+
<pre>
+
  gpio -g export 4 in
+
  gpio -g mode 4 up
+
</pre>
+
 
+
You can then use GPIO-4 as an input in your Python, Shell, Java, etc. programs without the use
+
of an external resistor to pull the pin high. (If that's what you were after - for example, a simple push
+
button switch taking the pin to ground.)
+
 
+
A fully working example of a shell script using the GPIO pins
+
can be found at http://project-downloads.drogon.net/files/gpioExamples/tuxx.sh.
+
 
+
====GPIO Driving Example (C)====
+
This must be done as root. To change to the root user:
+
<pre>sudo -i</pre>
+
You must also get and install the bcm2835 library, which supports
+
GPIO and SPI interfaces. Details and downloads
+
from  http://www.open.com.au/mikem/bcm2835
+
 
+
<pre>
+
 
+
// blink.c
+
//
+
// Example program for bcm2835 library
+
// Blinks a pin on an off every 0.5 secs
+
//
+
// After installing bcm2835, you can build this
+
// with something like:
+
// gcc -o blink -l rt blink.c -l bcm2835
+
// sudo ./blink
+
//
+
// Or you can test it before installing with:
+
// gcc -o blink -l rt -I ../../src ../../src/bcm2835.c blink.c
+
// sudo ./blink
+
//
+
// Author: Mike McCauley (mikem@open.com.au)
+
// Copyright (C) 2011 Mike McCauley
+
// $Id: RF22.h,v 1.21 2012/05/30 01:51:25 mikem Exp $
+
 
+
#include <bcm2835.h>
+
 
+
// Blinks on RPi pin GPIO 11
+
#define PIN RPI_GPIO_P1_11
+
 
+
int main(int argc, char **argv)
+
{
+
    // If you call this, it will not actually access the GPIO
+
    // Use for testing
+
//    bcm2835_set_debug(1);
+
 
+
    if (!bcm2835_init())
+
return 1;
+
 
+
    // Set the pin to be an output
+
    bcm2835_gpio_fsel(PIN, BCM2835_GPIO_FSEL_OUTP);
+
 
+
    // Blink
+
    while (1)
+
    {
+
// Turn it on
+
bcm2835_gpio_write(PIN, HIGH);
+
+
// wait a bit
+
delay(500);
+
+
// turn it off
+
bcm2835_gpio_write(PIN, LOW);
+
+
// wait a bit
+
delay(500);
+
    }
+
 
+
    return 0;
+
}
+
</pre>
+
 
+
====GPIO Driving Example (Perl)====
+
This must be done as root. To change to the root user:
+
<pre>sudo su -</pre>
+
Supports GPIO and SPI interfaces.
+
You must also get and install the bcm2835 library. Details and downloads
+
from  http://www.open.com.au/mikem/bcm2835
+
You must then get and install the Device::BCM2835 perl library from CPAN
+
http://search.cpan.org/~mikem/Device-BCM2835-1.0/lib/Device/BCM2835.pm
+
<pre>
+
use Device::BCM2835;
+
use strict;
+
 
+
# call set_debug(1) to do a non-destructive test on non-RPi hardware
+
#Device::BCM2835::set_debug(1);
+
Device::BCM2835::init()
+
|| die "Could not init library";
+
 
+
# Blink pin 11:
+
# Set RPi pin 11 to be an output
+
Device::BCM2835::gpio_fsel(&Device::BCM2835::RPI_GPIO_P1_11,
+
                            &Device::BCM2835::BCM2835_GPIO_FSEL_OUTP);
+
 
+
while (1)
+
{
+
    # Turn it on
+
    Device::BCM2835::gpio_write(&Device::BCM2835::RPI_GPIO_P1_11, 1);
+
    Device::BCM2835::delay(500); # Milliseconds
+
    # Turn it off
+
    Device::BCM2835::gpio_write(&Device::BCM2835::RPI_GPIO_P1_11, 0);
+
    Device::BCM2835::delay(500); # Milliseconds
+
}
+
 
+
 
+
</pre>
+
 
+
 
+
==== GPIO Driving Example (C#) ====
+
RaspberryPiDotNet library is available at https://github.com/cypherkey/RaspberryPi.Net/.
+
The library includes a GPIOFile and GPIOMem class. The GPIOMem requires compiling Mike McCauley's bcm2835 library above in to a shared object.
+
 
+
<pre>
+
using System;
+
using System.Collections.Generic;
+
using System.Linq;
+
using System.Text;
+
using RaspberryPiDotNet;
+
using System.Threading;
+
 
+
namespace RaspPi
+
{
+
    class Program
+
    {
+
        static void Main(string[] args)
+
        {
+
            // Access the GPIO pin using a static method
+
            GPIOFile.Write(GPIO.GPIOPins.GPIO00, true);
+
 
+
            // Create a new GPIO object
+
            GPIOMem gpio = new GPIOMem(GPIO.GPIOPins.GPIO01);
+
            gpio.Write(false);
+
        }
+
    }
+
}
+
</pre>
+
 
+
 
+
====GPIO Driving Example (Ruby)====
+
 
+
This example uses the WiringPi Ruby Gem: http://pi.gadgetoid.co.uk/post/015-wiringpi-now-with-serial which you can install on your Pi with "gem install wiringpi"
+
 
+
<pre>
+
MY_PIN = 1
+
 
+
require 'wiringpi'
+
io = WiringPi::GPIO.new
+
io.mode(MY_PIN,OUTPUT)
+
io.write(MY_PIN,HIGH)
+
io.read(MY_PIN)
+
</pre>
+
  
 
==MIPI CSI-2==
 
==MIPI CSI-2==
  
On the production board<ref>http://www.raspberrypi.org/wp-content/uploads/2012/04/Raspberry-Pi-Schematics-R1.0.pdf</ref>, the Raspberry Pi Foundation design brings out the MIPI CSI-2 (Camera Serial Interface<ref>http://www.mipi.org/specifications/camera-interface</ref>) to a 15-way flat flex connector S5, between the Ethernet and HDMI connectors. A compatible camera has been discussed as working in tests and is planned for release at a later date.<ref>http://www.raspberrypi.org/forum/projects-and-collaboration-general/complex-camera-peripherials#p72602</ref>.
+
On the production board<ref>http://www.raspberrypi.org/wp-content/uploads/2012/04/Raspberry-Pi-Schematics-R1.0.pdf</ref>, the Raspberry Pi Foundation design brings out the MIPI CSI-2 (Camera Serial Interface<ref>http://www.mipi.org/specifications/camera-interface</ref>) to a 15-way flat flex connector S5, between the Ethernet and HDMI connectors. A compatible camera<ref>http://elinux.org/Rpi_Camera_Module</ref> with 5 Megapixels and 1080p video resolution was released in May 2013.
<!-- This is misleading as it implies that cheap cameras from other devices can be used. CSI appears to be a generic interface with secret device-specific requirements so these devices must have drivers to be relevant (and currently only the VideoCore has access to the CSI hardware).
+
 
+
is Sony sub-LVDS same as MIPI CSI-2? Sony IMX020 5Mbip module is available for $5-7 (SE K850i replacement camera).
+
 
+
Looks like Nokia N95 uses CSI-2 5Mpix camera module with autofocus. ~$15 replacement part.
+
-->
+
  
 
==DSI==
 
==DSI==

Latest revision as of 14:42, 3 July 2015


Back to the Hub.


Hardware & Peripherals:

Hardware and Hardware History.

Low-level Peripherals and Expansion Boards.

Screens, Cases and Other Peripherals.


Introduction

In addition to the familiar USB, Ethernet and HDMI ports, the Raspberry Pi offers the ability to connect directly to a variety of electronic devices. These include:

  • Digital outputs: turn lights, motors, or other devices on or off
  • Digital inputs: read an on or off state from a button, switch, or other sensor
  • Communication with chips or modules using low-level protocols: SPI, I²C, or serial UART

Connections are made using GPIO ("General Purpose Input/Output") pins. Unlike USB, etc., these interfaces are not "plug and play" and require care to avoid miswiring. The Raspberry PI GPIOs use 3.3V logic levels, and can be damaged if connected directly to 5V levels (as found in many older digital systems) without level-conversion circuitry.

Note that no analogue input or output is available. However, add-on boards such as the Rpi Gertboard provide this capability.

Links


General Purpose Input/Output (GPIO)

Model A and B (Original)

P1 Header

thumb 26-pin GPIO header layout. Note that Rev 1 PCBs had different assignments for pins 3, 5, and 13. |
RPi P1 header.png

The Raspberry Pi Model A and B boards have a 26-pin 2.54 mm (100 mil)[1] expansion header, marked as P1, arranged in a 2x13 strip. They provide 8 GPIO pins plus access to I²C, SPI, UART), as well as +3.3 V, +5 V and GND supply lines. Pin one is the pin in the first column and on the bottom row. [2]

Revision 1 PCBs: Raspberry Pis with a revision 1 PCB (September 2012 or earlier) have a different pin assignment on the P1 connector:

  • P1 pin 3 is GPIO 0 / SDA0 (not GPIO 2)
  • P1 pin 5 is GPIO 1 / SCL0 (not GPIO 3)
  • P1 pin 13 is GPIO 21 (not GPIO 27)

Revision 1 PCBs also do not have the P5 header (see below). See this discussion for more details of the changes between Rev 1 and Rev 2 PCBs.

P2 header

The P2 header is the VideoCore JTAG and used only during the production of the board. It cannot be used as the ARM JTAG [3]. This connector is unpopulated in Rev 2.0 boards.

RPi P2 header.png

Useful P2 pins:

  • Pin 1 - 3.3V (same as P1-01, 50 mA max current draw across both of them)
  • Pin 7 - GND
  • Pin 8 - GND

P3 header

The P3 header, unpopulated, is the LAN9512 JTAG [4].

RPi P3 header.png

Useful P3 pins:

  • Pin 7 - GND

P5 header

The P5 header was added with the release of the Revision 2.0 PCB design.

RPi P5 header.png

P5 Header pinout, top row

As seen from the back of the board:

Pin Number Pin Name Rev2 Hardware Notes Alt 0 Function Other Alternative Functions
P5-01 5V0 Supply through input poly fuse
P5-03 GPIO28 I2C0_SDA ALT2 = PCM_CLK
P5-05 GPIO30 ALT2 = PCM_DIN ALT3 = UART0_CTS ALT5 = UART1_CTS
P5-07 GND

P5 Header pinout, bottom row

As seen from the back of the board:

Pin Number Pin Name Rev2 Hardware Notes Alt 0 Function Other Alternative Functions
P5-02 3.3 V 50 mA max (combined with P1)
P5-04 GPIO29 I2C0_SCL ALT2 = PCM_FS
P5-06 GPIO31 ALT2 = PCM_DOUT ALT3 = UART0_RTS ALT5 = UART1_RTS
P5-08 GND
Slanted P5 header

Note that the connector is intended to be mounted on the bottom of the PCB, so that for those who put the connector on the top side, the pin numbers are mirrored. Pin 1 and pin 2 are swapped, pin 3 and 4, etc.

An alternative way to attach this header is on top, at a slant away from the P1 header.

The new header can provide a second I²C channel (SDA + SCL) and handshake lines for the existing UART (TxD and RxD), or it can be used for an I2S (audio codec chip) interface using the PCM signals CLK, FS (Frame Sync), Din and Dout.

Note that the connector is placed JUST off-grid with respect to the P1 connector.

P6 header

The P6 header was added with the release of the Revision 2.0 PCB design.

RPi P6 header.png

P6 Pinout

Pin Number Pin Name Rev2 Hardware Notes
P6-01 RUN Short to ground to reset the BCM2835
P6-02 GND

A reset button can be attached to the P6 header.[5] Momentarily shorting the two pins of P6 together will cause a soft reset of the CPU (which can also 'wake' the Pi from halt/shutdown state).

Model A+, B+ and B2

Model A+
Models B+, B2
Connector pinout


The Raspberry Pi Model A+ and B+ boards, and the Pi 2 Model B, have a 40-pin header marked J8, arranged as 2x20 pins. The first 26 pins are the same as P1 on the A/B boards, with the remaining 14 pins providing additional GPIO and ground pins, and an EEPROM ID feature for auto-configuration with add-on "HAT" boards.[6]

Interfacing with GPIO pins

GPIO voltage levels are 3.3 V and are not 5 V tolerant. There is no over-voltage protection on the board - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board.

All the GPIO pins can be reconfigured to provide alternate functions, SPI, PWM, I²C and so. At reset only pins GPIO 14 & 15 are assigned to the alternate function UART, these two can be switched back to GPIO to provide a total of 17 GPIO pins[7]. Each of their functions and full details of how to access are detailed in the chipset datasheet [8].

Each GPIO can interrupt, high/low/rise/fall/change.[9][10] There is currently no support for GPIO interrupts in the official kernel, however a patch exists, requiring compilation of modified source tree.[11] The 'Raspbian "wheezy"' [12] version that is currently recommended for starters already includes GPIO interrupts.

GPIO input hysteresis (Schmitt trigger) can be on or off, output slew rate can be fast or limited, and source and sink current is configurable from 2 mA up to 16 mA. Note that chipset GPIO pins 0-27 are in the same block and these properties are set per block, not per pin. See GPIO Datasheet Addendum - GPIO Pads Control. Particular attention should be applied to the note regarding SSO (Simultaneous Switching Outputs): to avoid interference, driving currents should be kept as low as possible.

The available alternative functions and their corresponding pins are detailed below. These numbers are in reference to the chipset documentation and may not match the numbers exposed in Linux. Only fully usable functions are detailed, for some alternative functions not all the necessary pins are available for the funtionality to be actually used.

There is also some information on the Tutorial on Easy GPIO Hardware & Software.

Kernel boot messages go to the UART at 115200 bit/s - there are more details on the serial port page.


P1 Header pinout, top row

Pin Number Pin Name Rev1 Pin Name Rev2 Hardware Notes Alt 0 Function Other Alternative Functions
P1-02 5V0 Supply through input poly fuse    
P1-04 5V0 Supply through input poly fuse    
P1-06 GND      
P1-08 GPIO 14 Boot to Alt 0 -> UART0_TXD ALT5 = UART1_TXD
P1-10 GPIO 15 Boot to Alt 0 -> UART0_RXD ALT5 = UART1_RXD
P1-12 GPIO 18   PCM_CLK ALT4 = SPI1_CE0_N ALT5 = PWM0
P1-14 GND      
P1-16 GPIO23 ALT3 = SD1_CMD ALT4 = ARM_RTCK
P1-18 GPIO24 ALT3 = SD1_DAT0 ALT4 = ARM_TDO
P1-20 GND      
P1-22 GPIO25 ALT3 = SD1_DAT1 ALT4 = ARM_TCK
P1-24 GPIO08 SPI0_CE0_N
P1-26 GPIO07 SPI0_CE1_N

P1 Header pinout, bottom row

Pin Number Pin Name Rev1 Pin Name Rev2 Hardware Notes Alt 0 Function Other Alternative Functions
P1-01 3.3 V 50 mA max (01 & 17)    
P1-03 GPIO 0 GPIO 2 1K8 pull up resistor I2C0_SDA / I2C1_SDA
P1-05 GPIO 1 GPIO 3 1K8 pull up resistor I2C0_SCL / I2C1_SCL
P1-07 GPIO 4 GPCLK0 ALT5 = ARM_TDI
P1-09 GND      
P1-11 GPIO17 ALT3 = UART0_RTS ALT4 = SPI1_CE1_N ALT5 = UART1_RTS
P1-13 GPIO21 GPIO27 PCM_DOUT / reserved ALT4 = SPI1_SCLK ALT5 = GPCLK1 / ALT3 = SD1_DAT3 ALT4 = ARM_TMS
P1-15 GPIO22 ALT3 = SD1_CLK ALT4 = ARM_TRST
P1-17 3.3 V 50 mA max (01 & 17)    
P1-19 GPIO10 SPI0_MOSI
P1-21 GPIO9 SPI0_MISO
P1-23 GPIO11 SPI0_SCLK
P1-25 GND      


Colour legend
+5 V
+3.3 V
Ground, 0V
UART
GPIO
SPI
I²C

KiCad symbol: File:Conn-raspberry.lib[13]

Pin 3 (SDA0) and Pin 5 (SCL0) are preset to be used as an I²C interface. So there are 1.8 kohm pulls up resistors on the board for these pins.[14]

Pin 12 supports PWM.

It is also possible to reconfigure GPIO connector pins P1-7, 15, 16, 18, 22 (chipset GPIOs 4 and 22 to 25) to provide an ARM JTAG interface.[15] However ARM_TMS is not available on the GPIO connector (chipset pin 12 or 27 is needed). Chipset pin 27 is available on S5, the CSI camera interface however.

It is also possible to reconfigure GPIO connector pins P1-12 and 13 (chipset GPIO 18 and 21) to provide an I2S (a hardware modification may be required[16]) or PCM interface.[17] However, PCM_FS and PCM_DIN (chipset pins 19 and 20) are needed for I2S or PCM.

A second I²C interface (GPIO02_ALT0 is SDA1 and GPIO03_ALT0 is SCL1) and two further GPIOs (GPIO05_ALT0 is GPCLK1, and GPIO27) are available on S5, the CSI camera interface.

Referring to pins on the Expansion header

The header is referred to as "The GPIO Connector (P1)". To avoid nomenclature confusion between Broadcom signal names on the SoC and pin names on the expansion header, the following naming is highly recommended:

  • The expansion header is referred to as "Expansion Header" or "GPIO Connector (P1)"
  • Pins on the GPIO connector (P1) are referred to as P1-01, etc.
  • Names GPIO0, GPIO1, GPIOx-ALTy, etc. refer to the signal names on the SoC as enumerated in the Broadcom datasheet, where "x" matches BCM2835 number (without leading zero) and "y" is the alternate number column 0 to 5 on page 102-103 of the Broadcom document. For example, depending on what you are describing, use either "GPIO7" to refer to a row of the table, and "GPIO7-ALT0" would refer to a specific cell of the table.
  • When refering to signal names, the Broadcom name should be modified slightly to minimize confusion. The Broadcom SPI bus pin names are fine, such as "SPI0_*" and "SPI1_*", but they did not do the same on the I²C and UART pins. Instead of using "SDA0" and "SCL0", "I2C0_SDA" and "I2C0_SCL" should be used; and "UART0_TXD" and "UART0_RXD" instead of "TX" or "TXD" and "RX" or "RXD".

Power pins

The maximum permitted current draw from the 3.3 V pins is 50 mA.

Maximum permitted current draw from the 5 V pin is the USB input current (usually 1 A) minus any current draw from the rest of the board.[18]

  • Model A: 1000 mA - 500 mA -> max current draw: 500 mA
  • Model B: 1000 mA - 700 mA -> max current draw: 300 mA

Be very careful with the 5 V pins P1-02 and P1-04, because if you short 5 V to any other P1 pin you may permanently damage your RasPi. Before probing P1, it is a good idea to strip short pieces of insulation off a wire and push them over the 5 V pins are not accidentally shorted with a probe.

GPIO hardware hacking

The complete list of chipset GPIO pins which are available on the GPIO connector is:
0, 1, 4, 7, 8, 9, 10, 11, 14, 15, 17, 18, 21, 22, 23, 24, 25

(on the Revision2.0 RaspberryPis, this list changes to: 2, 3, 4, 7, 8, 9, 10, 11, 14, 15, 17, 18, 22, 23, 24, 25, 27, with 28, 29, 30, 31 additionally available on the P5 header)

As noted above, P1-03 and P1-05 (SDA0 and SCL0 / SDA1 and SCL1) have 1.8 kohm pull-up resistors to 3.3 V.

If 17 GPIOs are not sufficient for a project, there are a few other signals potentially available, with varying levels of software and hardware (soldering iron) hackery skills:

GPIO02, 03, 05 and 27 are available on S5 (the CSI interface) when a camera peripheral is not connected to that socket, and are configured by default to provide the functions SDA1, SCL1, CAM_CLK and CAM_GPIO respectively. SDA1 and SCL1 have 1K6 pull-up resistors to 3.3 V.

GPIO06 is LAN_RUN and is available on pad 12 of the footprint for IC3 on the Model A. On Model B, it is in use for the Ethernet function.

There are a few other chipset GPIO pins accessible on the PCB but are in use:

  • GPIO16 drives status LED D5 (usually SD card access indicator)
  • GPIO28-31 are used by the board ID and are connected to resistors R3 to R10 (only on Rev1.0 boards).
  • GPIO40 and 45 are used by analogue audio and support PWM. They connect to the analogue audio circuitry via R21 and R27 respectively.
  • GPIO46 is HDMI hotplug detect (goes to pin 6 of IC1).
  • GPIO47 to 53 are used by the SD card interface. In particular, GPIO47 is SD card detect (this would seem to be a good candidate for re-use). GPIO47 is connected to the SD card interface card detect switch; GPIO48 to 53 are connected to the SD card interface via resistors R45 to R50.


Internal Pull-Ups & Pull-Downs

The GPIO ports include the ability to enable and disable internal pull-up or pull-down resistors (see below for code examples/support of this):

  • Pull-up is 50 kOhm - 65 kOhm
  • Pull-down is 50 kOhm - 60 kOhm

Driver support

The Foundation will not include a GPIO driver in the initial release, standard Linux GPIO drivers should work with minimal modification.[19]

The community implemented SPI and I²C drivers [20], which will be integrated with the new Linux pinctrl concept in a later version of the kernel. (On Oct. 14 2012, it was already included in the latest raspbian image.) A first compiled version as Linux modules is available to install on the 19/04/2012 Debian image, including 1-wire support[21]. The I²C and SPI driver uses the hardware modules of the microcontroller and interrupts for low CPU usage, the 1-wire support uses bitbanging on the GPIO ports, which results in higher CPU usage.

GordonH[22] wrote a (mostly) Arduino compatible/style WiringPi library in C for controlling the GPIO pins.

A useful tutorial on setting up I²C driver support can be found at Robot Electronics - look for the downloadable document rpi_i2c_setup.doc

SPI

There is one SPI bus brought out to the header: RPi_SPI

I²C

There are two I²C-buses on the Raspberry Pi: One on P1, and one on P5.

Note that there's a bug concerning I²C-clock-stretching, so don't use I²C-devices which use clock-stretching directly with the Raspberry Pi, or use a workaround. Details about this bug can be found at:

MIPI CSI-2

On the production board[23], the Raspberry Pi Foundation design brings out the MIPI CSI-2 (Camera Serial Interface[24]) to a 15-way flat flex connector S5, between the Ethernet and HDMI connectors. A compatible camera[25] with 5 Megapixels and 1080p video resolution was released in May 2013.

DSI

On the production board, the Raspberry Pi Foundation design brings out the DSI (Display Serial Interface[26]) to a 15-way flat flex connector labelled S2, next to Raspberry Pi logo. It has two data lanes and a clock lane, to drive a possible future LCD screen device. Some smart phone screens use DSI[27].

CEC

HDMI-CEC (Consumer Electronics Control for HDMI) is supported by hardware but some driver work will be needed and currently isn't exposed into Linux userland. Eben notes that he has seen CEC demos on the Broadcom SoC they are using.

libCEC with Raspberry Pi support has been included in OpenELEC and will be included in Raspbmc RC4.[28]

For more information about HDMI-CEC and what you could do with it on the Raspberry Pi please see the CEC (Consumer Electronics Control) over HDMI article.

References

  1. raspberrypi.org
  2. raspberrypi.org
  3. http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894
  4. http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5894
  5. raspi.tv
  6. raspberrypi.org
  7. raspberrypi.org
  8. raspberrypi.org
  9. http://www.raspberrypi.org/archives/384#comment-5217
  10. http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
  11. http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=7509
  12. http://www.raspberrypi.org/downloads
  13. http://www.raspberrypi.org/forum/projects-and-collaboration-general/gpio-header-pinout-clarification/page-2
  14. http://www.raspberrypi.org/forum/features-and-requests/easy-gpio-hardware-software/page-6/#p56480
  15. http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.1
  16. Forum:Sad about removal of I2S. Why was this change made?
  17. http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.2
  18. http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1536#postid-21841
  19. http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1278.0
  20. http://www.bootc.net/projects/raspberry-pi-kernel/
  21. http://www.raspberrypi.org/phpBB3/viewtopic.php?p=86172#p86172
  22. http://www.raspberrypi.org/forum/general-discussion/wiring-for-the-raspberry-pis-gpio
  23. http://www.raspberrypi.org/wp-content/uploads/2012/04/Raspberry-Pi-Schematics-R1.0.pdf
  24. http://www.mipi.org/specifications/camera-interface
  25. http://elinux.org/Rpi_Camera_Module
  26. http://www.mipi.org/specifications/display-interface
  27. http://en.wikipedia.org/wiki/Display_Serial_Interface
  28. http://blog.pulse-eight.com/2012/08/01/libcec-1-8-0-a-firmware-upgrade-and-raspberry-pi-support/