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History

Richard A. Healy cdfce0d01b add openocd argument and raspboot device vars		5 years ago
..
.cargo	Change to new aarch64-unknown-none-softloat target.	5 years ago
raspi3_boot	Change to new aarch64-unknown-none-softloat target.	5 years ago
src	Fix correct term usec for microseconds	5 years ago
Cargo.lock	Update toolchain and bump dependency versions	5 years ago
Cargo.toml	Update toolchain and bump dependency versions	5 years ago
Makefile	add openocd argument and raspboot device vars	5 years ago
README.md	Fix correct term usec for microseconds	5 years ago
kernel8	Change to new aarch64-unknown-none-softloat target.	5 years ago
kernel8.img	Change to new aarch64-unknown-none-softloat target.	5 years ago
link.ld	Alignment. Binaries from newer Rust version.	6 years ago

README.md

Tutorial 09 - Delays

It is very important to wait precise amounts of time while you are interfacing with low level hardware. In this tutorial, we'll cover thee ways. One is CPU frequency dependent (and useful if wait time is given in CPU clock cycles), the other two are µs based.

delays.rs

delays::wait_cycles(cyc: u32) this is very straightforward, we execute the nop instruction n times.

delays::wait_usec(n: u32) this implementation uses ARM system registers (available on all AArch64 CPUs).

delays::SysTmr::wait_usec_st(&self, n: u64) is a BCM specific implementation, which uses the System Timer peripheral (not available on qemu).

uart.rs

We can now conveniently use delays::wait_cycles() in Uart::init().

main.rs

We test our different wait implementations.