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Difference between revisions of "Talk:RPi Low-level peripherals"

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I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram.
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I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice used I suggest adding a photo that clearly labels the connector pins and the corner of the board is visible.
  
 
I see the pad for pin 1 on the board is square (visible on the solder side of the board). There is also a P1 designation on the component side of the board. By component side I mean the side with the through hole components.
 
I see the pad for pin 1 on the board is square (visible on the solder side of the board). There is also a P1 designation on the component side of the board. By component side I mean the side with the through hole components.
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--[[user:danpeirce|danpeirce]]

Revision as of 09:49, 20 August 2012

Save old header pinout table

Header Pinout:

Top Row 5V0 DNC GND UART0_TXD UART0_RXD GPIO1_PWM DNC GPIO4 GPIO5 DNC GPIO6 SPI_CE0_N SPI_CE1_N
Bottom Row 3V3 I2C0_SDA I2C0_SCL GPIO7 DNC GPIO0 GPIO2 GPIO3 DNC SPI_MOSI SPI_MISO SPI_SCLK DNC


Colour legend
+5V
+3.3V
Do not connect
UART
GPIO
SPI
I2C

Donster2k: "Kernel boot messages go to the UART at 115200bps." - This should be configurable as a kernel parameter. It is the bootloader that will always output to the uart on the header, correct?

Donster2k: What will be the power-on states of the GPIO pins?

Donster2k: USB2 spec states that the max current draw from a port (either powered hub or PC's usb) is 500mA. Does this mean that the revB module will need to be powered via a usb charger?

Donster2k: Most of the reference links to the forum are broken. Probably happened when they moved the forum.

naicheben: The color legend is fine for the table "Header Pinout" but it does not correspond to the GPIOs.gif as stated below the GIF. Shouldn't we better use same color "coding"?

Russell: I was just reading the datasheet "BCM2835 ARM Peripherals" and found that section 1.3 requires memory barrier operations to be used when accessing peripherals. This says to me that use user space access to the GPIO or any other peripheral is somewhat dangerous/error prone. Unless the kernel stopped from using any other peripheral, these registers would have to be accessed atomically, with barrier instructions, from a kernel driver.


What is this "1k8" referenced several times throughout the page? Do we mean to say "1kΩ"? If so, any objection to changing all those eights to ohms? Or if for some reason we're not comfortable using the ohm (omega) symbol, even just "1k" would be clearer to me than "1k8". Jstrout 13:43, 30 May 2012 (UTC)

No, it doesn't mean 1 kOhm. It is a standard syntax meaning 1.8 kOhm. It is written that way because when writing values, especially if writing very small, a decimal point could easily be rubbed off or missed, whereas a k is much clearer. If it is confusing, I don't think anyone would object to writing 1k8 Ohms, though the context normally makes it clear. --Polymerheart 21:14, 16 July 2012 (UTC)

Answers from Grumpy Mike From Donster2k: What will be the power-on states of the GPIO pins? ..... They are all inputs except GPIO 14 & 15 which are serial input / output and can be used to log in. From Jstrout What is this "1k8" ...... it is short for one point eight K ohms. It is so you can't accidentally miss the decimal point.

The pin out on this page is very bad, it should referee to all the pins as GPIO numbers. Most of the alternative pin functions are only one possible out of 6 and they initialise as inputs anyway.


I can't recall seeing designations like top row, bottom row, left and right on a pinout for a connector. This would be because there is much ambiguity (in general) about which of the four sides of the board should be top. More typically everything is referenced relative to a key like the pad for PIN 1. Since the connector is at the board edge there could be a great deal more clarity for the novice if the board edge were marked in the diagram. I notice now that if I click on the source link under the pin diagram I am taken to another diagram that actually includes enough of the board that it is clear which row is at the board edge. For novice used I suggest adding a photo that clearly labels the connector pins and the corner of the board is visible.

I see the pad for pin 1 on the board is square (visible on the solder side of the board). There is also a P1 designation on the component side of the board. By component side I mean the side with the through hole components. --danpeirce