ARM Timer for BCM2835 (Raspberry Pi)

Description

• Adds functions to start and read ARM timer which runs at higher speeds (250 MHz) and gives finer timing resolution compared to system timer (runs at 1 MHz). However, its clock source can be dynamically change (ie low power mode etc), hence timing accuracy may change based on this behavior of the system.
• Suggested use for short busy waits (ie less than 5000 nsec). Based on experiments, ~180-200 nsec delays seem achievable, shorter delays seem not possible (see output of test program)
• Tested on, Raspberry Pi 1 Model B, Raspbian Buster, kernel 5.10.63.

Usage

• #include "arm_timer.h" in your code along with #include <bcm2835.h>.
• First bcm2835_init() then call bcm2835_arm_timer_init() and bcm2835_arm_timer_enable().
• See test.c for further detail.
• After build, run with sudo.

Resources

• Reference work
• Based on bcm2835 library
• ARM peripheral details document
• Origin repo at github.com/eardali

License

Distributed under the terms of the MIT license.