Difference between revisions of "Rpi Low-level peripherals"

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The Rpi allows peripherals to access the CPU by exposing the in and outputs. The production board has a 26-pin 1.27mm (50mil) expansion header, arranged in a 2x13 strip. They provide 8 GPIO pins plus access to I2C, SPI, UART), as well as +3V3, +5V and GND supply lines.  Pin one is column 0 on the bottom row. <ref>http://www.raspberrypi.org/archives/384</ref>
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#REDIRECT [[RPi Low-level peripherals]]
 
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Voltage levels are 3v3.  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.
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It is also possible to reconfigure some of the pins to provide a second I2C interface. [no-ref]
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Kernel boot messages go to the UART at 115200bps.
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'''Pinout:'''
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{| border="1" style="text-align:center;"
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| '''Top Row''' || bgcolor="red" | <span style="color:white">5V0</span> || DNC || bgcolor="black" | <span style="color:white">GND</span> || bgcolor="yellow" | TXD || bgcolor="yellow" | RXD || bgcolor="lime" | GPIO1 || DNC || bgcolor="lime" | GPIO4 || bgcolor="lime" | GPIO5 || DNC || bgcolor="lime" | GPIO6 || bgcolor="purple" | <span style="color:white">SPI_CE0_N</span> || bgcolor="purple" | <span style="color:white">SPI_CE1_N</span>
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|-
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| '''Bottom Row''' || bgcolor="orange" | 3V3 || bgcolor="cyan" | SDA0 || bgcolor="cyan" | SCL0 || bgcolor="lime" | GPIO7 || DNC || bgcolor="lime" | GPIO0 || bgcolor="lime" | GPIO2 || bgcolor="lime" | GPIO3 || DNC || bgcolor="purple" | <span style="color:white">SPI_MOSI</span> || bgcolor="purple" | <span style="color:white">SPI_MISO</span> || bgcolor="purple" | <span style="color:white">SPI_SCLK</span> || DNC
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|}
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{| border="1"
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! Colour legend
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|-
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| bgcolor="red" | <span style="color:white">+5V</span>
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|-
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| bgcolor="orange" | +3.3V
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|-
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| Do not connect
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|-
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| bgcolor="yellow" | UART
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|-
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| bgcolor="lime" | GPIO
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|-
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| bgcolor="purple" | <span style="color:white">SPI</span>
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|-
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| bgcolor="cyan" | I2C
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|}
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Colour-coded Image: https://sites.google.com/site/burngatehouse/home/drawings/GPIOs.gif
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==Power pins==
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::''see also [[Rpi power]]''
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Maximum permitted current draw from the 3v3 pin is 50mA.
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Maximum permitted current draw from the 5v pin is the USB input current (usually 1A) minus any current draw from the rest of the board, or about 650 mA. <ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1536#postid-21841</ref>
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==General Purpose Input/Output (GPIO)==
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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. For more information see:[http://en.wikipedia.org/wiki/GPIO the wikipedia article].
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On the production board, all the UART, SPI and I2C pins can be reconfigured as GPIO pins, to provide a total of 17 GPIO pins.<ref>http://www.raspberrypi.org/archives/384</ref>
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At least some of the GPIO pins support PWM.<ref>http://twitter.com/#!/Raspberry_Pi/status/140548306886602752</ref>
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Each GPIO can interrupt, high/low/rise/fall/change.<ref>http://www.raspberrypi.org/archives/384#comment-5217</ref>
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It is also possible to reconfigure some of the pins to provide an ARM JTAG interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.1</ref>
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It is also possible to reconfigure some of the pins to provide an I2S or PCM interface.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1288.2</ref>
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===Driver support===
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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>
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The Foundation will not include a SPI driver in the initial release, we hope the community might write one.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1278.0</ref>
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The Foundation will not include an I2C driver in the initial release, we hope the community might provide one, standard linux I2C drivers should work with minimal modification.<ref>http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1202</ref>
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===Code examples===
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Here, some code examples should be shown.
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==MIPI CSI-2==
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On the production board, we bring out the MIPI CSI-2 interface to pads for an unpopulated 15-way flat flex connector
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==DSI==
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On the production board, we bring out the DSI interface to pads for an unpopulated 15-way flat flex connector
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==CEC==
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HDMI-CEC is supported by hardware but some driver work will be needed and currently isn't exposed into Linux userland.
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Eben notes that he has seen CEC demos on the Broadcom SoC they are using.
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== References ==
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<references/>
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Latest revision as of 20:17, 28 January 2012