We were looking at WCH @Patrick_RISCV for a USB to serial chip to replace the CP210x, when we remembered a lot of chatter a few years ago about the CH552 series of ultra-low-cost 8051 microcontrollers with native USB. you can kinda sorta code these with Arduino https://hackaday.io/project/172143-ch55xduino and we thought it could be an interesting QT Py since it has so few pins but does cover the basic use cases: 4 ADC, UART, SPI and maybe even I2C with a bitbang connection? Still, for very very basic USB projects maybe it would be useful, particularly since it has a ROM USB bootloader. Here’s a simple design we whipped together. Since there isn’t a lot of muxing or IO available, MISO and A2 share the same pin. Some interesting unusual things to watch for: reset is backwards from how we’d expect, and bootloader mode is entered by pulling D+ to 3V? … // Read more: original article.
