Where to Find Documentation for GPIO Controller Pins of Pi4?

Question

I'm beginning bare metal programming on the Pi4. As a simple 'hello world' equivalent I'm trying to get the ACT led to blink. I have seen references that it is tied to the BCM2711 GPIO Controller pin 16. However, looking at the BCM2711 datasheet I can't find any references to this. Is this information available in a datasheet or an official documentation source somewhere?

Answer 1

The BCM2711 peripherals documentation can be found on the Foundation website.
https://datasheets.raspberrypi.org/bcm2711/bcm2711-peripherals.pdf

The GPIO is a superset of the earlier GPIO i.e. it is identical EXCEPT some pins have additional modes and the peripheral address differs between models. See https://www.raspberrypi.org/documentation/hardware/raspberrypi/peripheral_addresses.md

AFAIK there is no public documentation for the on-board interfaces e.g. ACT LED.

Exploring the gpiochip implementation in latest Raspberry Pi OS gives some hints about the on-board GPIO functions.

gpioinfo pinctrl-bcm2835

Update: The following may be of interest re the expansion GPIO.

gpioinfo raspberrypi-exp-gpio
gpiochip1 - 8 lines:
    line   0:      "BT_ON"       unused  output  active-high 
    line   1:      "WL_ON"       unused  output  active-high 
    line   2: "PWR_LED_OFF" "led1" output active-low [used]
    line   3: "GLOBAL_RESET" unused output active-high 
    line   4: "VDD_SD_IO_SEL" "vdd-sd-io" output active-high [used]
    line   5:   "CAM_GPIO"       unused  output  active-high 
    line   6:  "SD_PWR_ON" "sd_vcc_reg"  output  active-high [used]
    line   7:    "SD_OC_N"       unused   input  active-high 

Answer 2

Hi @Edward Chamberlain

Reviving this thread in Jul 2023 - I cannot find the pinout anywhere!

Any luck?