Open source != easy
Sharing software or hardware is not the only step to make open source projects accessible.
Developing with open programs, and affordable tools are important aspects too.
But many embedded systems purists would never accept to use Arduino in a serious project, and from the difficult Twiz experience with users, it seemed important to find a trade-off.
Luckily, the excellent work by Sandeep Mistry allows it reasonably:
Once the environment validated, it was possible to test the boards, it might seem simple but blinking LEDs can sometimes be very challenging, mostly in the Chinese manufacturer's office:
Back home, it took a while to validate all the firmware components.
The most complicated being the PPI, we found inspiration in the ex-arduino.org repos, and got it to work:
To reach this point, many steps were necessary, but the main trick was to use a logic analyser.
For those who only work with open tools, Sigrok can help, but the software by Saleae is free + cross platform and is quite practical: