This repo gets a trivial Zig program (blink an LED) working on an Arduino Uno (atmega328p). There is much hackery.
This was built using:
- Zig master some time between 0.6.0 and 0.7.0
- avr-libc 1:.0.0.+Atmel3.6.1-2
- binutils-avr 2.26.20160125+Atmel3.6.2-1+b1
- gcc-avr 1:5.4.0+Atmel3.6.1-2+b1
- avrdude 6.3-20171130+svn1429-2+b1
Those are Debian's names for the packages. Other distros may use different names.
Before trying to get Zig to work, I had to make sure I had a working C toolchain. This program builds and runs just fine.
It's actually possible to tell that this one's working, because the
LED blinks. The preprocessor symbol GCC is defined if we're building
with avr-gcc, which is a requirement to get this whole thing
working. If it's not defined, clang works. I didn't bother to find the
actual symbol the compiler provides; flip it manually.
This program is a bit more complicated, since it's got a version that uses an ISR. The Zig version does not know about interrupts.
A place to put constants and functions that would otherwise live in avr/io.h and avr/interrupt.h. Zig's translate-c got too confused on the actual AVR headers, so here we are.
A tiny Zig program to blink an LED using a delay loop.
A Zig version of the ISR version of blinker.c. Same as blink.zig, but
with an interrupt. Weird fact: llvm emits an sei instruction at the
start of the ISR.
This contains the actual point of this repo. The zig command line
uses Zig's -femit-asm switch to spit out avr assembler code. That
gets fed to GCC's ld, which is actually what llvm does to "support"
AVR. The linker sets up all the interrupt vectors and puts main in
the right place. For the C programs, The linked elf gets passed to
objcopy to make an intel ihex file. This last step is entirely
optional, since avrdude actually knows how to upload elf files. The
Zig path doesn't do it.
It also includes the %.dmp target, which is essential for knowing
whether the other steps are working correctly, and debugging them when
they're not.