Dark-side of the Raspberry Pi

BCM2835 Peripherals

BCM2835 contains the following peripherals which may safely be accessed by the ARM:

• One part of theses peripherals are routed from the BCM2835 chip pads to the 2×20 GPIO header in order to be freely accessible (as shown above).
• One other part of these peripherals are routed from the BCM2835 to some PI Zero board’s components such as USB for example.
• The remaining part is not connected outside the BCM3835.

GPIOs

Global purpose Input/Output (GPIO) is one function out of several multiplexed on each pad of the BROADCOM BCM2835 SOC soldered on the PI Zero V1.3 board. You will find details into the BCM2835 peripherals datasheet :

“Every GPIO pin can carry an alternate function. Up to 6 alternate function are available but not every pin has that many alternate functions.”

• Datasheet :

BCM2835 ARM peripherals

• Comprehensive Wiki :

https://elinux.org/RPi_BCM2835_GPIOs

• Interactive Pinout :

https://pinout.xyz/pinout/io_pi_zero#

Example of multiplexing on GPIO 18: