This is a sign of the times, [dmitry] one of the standards for designing new Linux on business cards is to use parts that can be found during the current component shortage. The generated board uses atsamd21 chip and simulates MIPS machine to boot Linux.
In addition to the construction details, we also like [dmitry] to outline many reasons for his decision. There are also many details about how the whole system actually works. For example, by using a 0.8mm PCB, the board can accept usb-c cables without additional connectors. There is another good explanation for MIPS MMU. Don’t forget that MIPS originated from risc-v, so many core details of MIPs are also applicable to risc-v (but not MMU). You will also find some criticisms of the DMA system of atsamd21. It seems to save the real estate of the chip. The DMA system stores the configuration data in the user’s memory, and these data must be loaded and unloaded every time the channel is switched.
At the end of the article, you will think that this may be the last atsamd21 project of [dimitry]. But we must admit that the result seems to be good. This is not the first business card Linux version we have seen. This really reminds us of the MIDI controller card we once saw.