Raspberry Pi v2 – function of pin P1-12 at power-up.

[bluestar]

1. Are all pins set to Alternate Function Mode 0 when the board powers-up?

2. If question 1 is true, then what function is set on header P1, pin 12? BCM2865 ARM Peripherals.pdf Table 6-31 indicates pin 12 in alt-0 mode would have a PW-M0 function. While, the Raspberry Pi Revision 2 schematics show GPIO18 coming out of IO1 is labeled GPIO_Gen1 (sheet 2 of 5) and it is directly wired to header P1 pin 12 and that pad is also labeled GPIO_Gen1 (also sheet 2 of 5). So I am confused as to which is correct.

3. The other possibility is that all pins default to GPIO mode when the board powers-up and to attain the special functions like, UART, I2C and SPI then each respective pin must be set to its respective alternate function mode.

[ChristophS]

Hello,
I Buyed a Raspberry B+ and installed WebIOPi a webinterface for controlling the GPIO. and install wiringpi. WiringPi brings the commandline-tool gpio. if you call

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 gpio readall

you see your configuration of gpio. Mine after a reboot is:
the most GPIO Pins are in Input-mode, except PIN 8 and 10 are in Mode ALT0 for UART RX0/TX0. but you can alter pin8 and 10 to in or output if you want to use them as an GPIO-Pin with

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 gpio mode -1(for pysical mode) 8 OUTPUT|INPUT 

or

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 gpio mode -1 10 OUT|IN 

to reset to normal mode

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 gpio mode -1 8 ALT0  # for UART Mode 

If you load via

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i2c-load

or sudo modprobe

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 i2c-bcm2708

the i2c-bcm2708 kernel-module, the pins 3 and 5 automatically turned to ALT0 to sda.1 and scl.1 for i2c-input

I hope that will help you a litte bit.
CSchultz

[bluestar]

Great Info.
Thanks.