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Adafruit CH552 QT Py - 8051 Dev Board with STEMMA QT

by Adafruit

What a cutie pie! Or is it... a QT Py? This diminutive dev board comes with a throwback processor - an 8-bit 8051!

This tiny core is a big change from something like the the ESP32-S3 QT Py with two 240MHz 32-bit cores, but there's lots of folks interested in the CH552 and given the smol size, it is a nice matchup for a smol board.

The CH552  is an 'enhanced' E8051 core microcontroller, compatible with MCS51 instruction set but with 8~15 times faster instruction execution speed. You can run this core at 16MHz and 3.3V logic, and it's gotbuilt-in 16K program FLASH memory and, 256-byte internal RAM plus 1K-byte internal xRAM (xRAM supports DMA. It's also got some cute tricks up it's sleeve, like 4 built-in ADC channels, capacitive touch support, 3 timers / PWM channels, hardware UART, SPI, and a full-speed USB device controller. The last one means it can act like a native USB device such as CDC serial or mouse/keyboard HID.

If you're interested in playing with this chip, we've wrapped it up in a QT Py format. The pinout and shape is Seeed Xiao compatible, with castellated pads so you can solder it flat to a PCB. It comes with our favorite connector - the STEMMA QT, a chainable I2C port that can be used with any of our STEMMA QT sensors and accessories. We also added an RGB NeoPixel and both a reset button and 'bootloader enter' button.

Please note! This is a minimal 8-bit microcontroller, and it definitely does not run CircuitPython or Micropython. It also doesn't really run Arduino. There's an Arduino 'board support package' we recommend, but the compiler is for C not C++, which means you cannot use any Arduino libraries. It's very very bare-bones and for hacking/experimenting with this '40 cent chip'

  • Same size, form-factor, and pin-out as Seeed Xiao
  • USB Type C connector¬†-¬†If you have only Micro B cables, this adapter will come in handy!
  • CH552 8-bit 8051¬†microcontroller core with 3.3V power/logic. Internal 16 MHz oscillator.
  • Native USB
  • Built in RGB NeoPixel LED
  • 10¬†GPIO pins:
    • A2 pin is the same as MOSI pin¬†(it's the hardware SPI port and one of only 4 ADC pns)https://github.com/DeqingSun/ch55xduino4 x 8-bit analog inputs on A0, A1, A2, and A3
    • 3 x PWM outputs
    • I2C port with STEMMA QT plug-n-play connector
    • Hardware UART
    • Hardware SPI
    • 4 x Capacitive Touch with no additional components required, on A0-A3 pins
  • 3.3V regulator with¬†600mA peak output
  • Reset switch and bootloader¬†for starting your project code over or entering USB ROM¬†bootloader mode
  • Really really small

Technical Details

RoHS 2 2011 65 EU Compliant RoHS 2 2015 863 EU Compliant