Firmware hacking
Yarns' source code is available under the MIT licence.
The code (along with the hardware description files) can be found in the yarns directory in our Eurorack modules git repository.
After having cloned the repository, don't forget to run git submodule init && git submodule update to make sure the sub-projects referenced in the code are also pulled.
Toolchain
If you don't mind installing Vagrant and VirtualBox a cozy environment for firmware hacking is available.
If you want to set up your own environment to build Yarns' code, an ARM EABI toolchain must be installed. Because of tight CPU and code size limits, we recommend you to use the same compiler version as we do: 4.8-2013-q4-major. Various pre-compiled binaries and source packages are available here.
The path to the toolchain binaries must be specified in the TOOLCHAIN_PATH variable in yarns/makefile.
To build the bootloader, use the following command:
make -f yarns/bootloader/makefile hex
To build the code, use the following command:
make -f yarns/makefile
If you modify lookup tables and want the big resources.cc file to be regenerated:
touch yarns/resources/resources.py && make -f yarns/makefile resources
Firmware programming
A first solution is to simply use the firmware update procedure. A .syx file for firmware upgrade can be generated with:
make -f yarns/makefile syx
The firmware can then be loaded into the module using the procedure described in the manual.
Past this point, we assume you know what you are doing and we are not responsible for any damage to your module!
The recommended solution for firmware programming is to use a JTAG interface and openOCD. We recommend Olimex' ARM-USB-OCD-H devices. An adapter must also be purchased for the mini-JTAG connector used by Yarns.
Upload the firmware with:
make -f yarns/makefile upload_combo_jtag_no_erase
Note that the upload_combo_jtag_no_erase command is used to prevent the FLASH to be entirely erased at each update – keeping the precious calibration data in place!