This document describes building the bootloader and other bare metal programs from source. This process requires a Linux PC, preferably Debian or Ubuntu or one of its derivatives. This will also work in a virtual machine and should work in WSL, but I have not verified this.
The cross-compiler is made up of three pieces: binutils, gcc, and Baselibc. All of these need to be built locally before they can be used to compile programs for Mackerel.
I've created a script to automate this process. If you'd prefer to do this manually or customize any part of it, refer to the script anyway. It will serve as a guide to downloading and building the various pieces of the toolchain.
Once you have the cross-compiler built and installed, the bootloader and other programs can be compiled by running make from the firmware folder. By default, this is will create programs for Mackerel-08. To build for Mackerel-10 instead, run make BOARD=mack10.
The bootloader is compiled to run from ROM. Other bare-metal programs run from RAM. This is set up in the Makefile.
To compile a new programs, add an entry in the Makefile.
On Mackerel-08, three 22V10 GAL chips provide the glue logic for the system. The logic equations for these are defined in the PLD directory. Compiling them into JED files requires the galasm tool. There's a Makefile in the PLD directory to build all of these JEDs, just run make.