The Ham CH552 Micro from Ham Studios is a tiny, breadboard-friendly development board for the famously inexpensive CH55x line of microcontrollers from WCH-IC. They are based on an 8051 core with a few peripherals, including USB in the CH552! This USB connection allows a small bootloader to run, making it Arduino-compatible thanks to some hard work from the Arduino community.
Despite its size and cost, the CH552 has all the peripherals you’d expect in a small 8-bit microcontroller. It has multiple timers, two UARTs, an ADC and comparator, dedicated PWM peripherals, plus 16K of flash, 256 bytes of instruction RAM (essentially acting as a cache) and 1k of what WCH calls “xRAM”, which seems to be general-purpose RAM that’s connected to the DMA bus. And with the addition of USB, the price seems almost too good to be true.
Ham Studios have added an onboard WS2812B RGB LED and put the chip on a very small, breadboard-friendly breakout board with a Micro-B USB connector. There are some open-source tools available for working with these chips if you want to avoid using Arduino, including ch55xtool and the Small Device C Compiler (sdcc). Because it uses an 8051 core, the instruction set is extremely well documented, and the special function register locations have been documented so you can access the peripherals from your code.
The board is small enough to fit inside all sorts of things. I could see myself putting one inside my laptop, wiring it into the USB bus, and adding some extra touch macro keys along the top edge of my keyboard. Or perhaps use one as a real-time co-processor for a Raspberry Pi.
If you’ve ever thought about checking out this line of microcontrollers, the Ham CH552 is a great way to get started!
