To build the ice40 DFU bootloader you will need the YosysHQ toolchain and an embedded risc-v cross compiler with newlib.
You can download pre built binaries from YosysHQ fpga-toolchain.
And you can download the risc-v embedded toolchain from xPack.
To build the DFU bootloader run:
make bootloader
By default this will build the DFU bootloader for the full size iCEBreaker FPGA
development board. If you want to build for a different platform you will have
to provide the BOARD= parameter.
For example to build the DFU bootloader for the iCEBreaker-bitsy V1.x you can run:
make BOARD=bitsy-v1 bootloader
In some cases the risc-v cross compiler has a different prefix than the default
riscv-none-elf-. You can adjust the prefix to the one you have installed on
your system using the CROSS= parameter.
For example on Arch Linux the riscv crosscompiler has the prefix
riscv64-unknown-elf- so you would build the bootloader by running:
make CROSS=riscv64-unknown-elf- bootloader
In some cases make does not recognize that it needs to rebuild the bitstreams
and firmware. For example when you change the BOARD= parameter. To clean all
the generated binary artifacts and force a full rebuild of the bootlader you
can run the following command:
make PRE_CLEAN=1 bootloader-clean
To flash the bootloader onto a target using iceprog you can run the following
command:
make prog-bootloader
or, if you need to run iceprog with root permissions:
make sudo-prog-bootloader
TODO: Add instructions on how to update the bootloader using dfu-util.