Adafruit's CH552 8051 QT Py Is a Tiny Modern Dev Board with a Vintage Twist

This ultra-compact <$5 board packs 10 GPIO, USB-C, a NeoPixel, and STEMMA QT around an E8051-based microcontroller

James Lewis
1 month ago

Adafruit's latest QT Py development board pays homage to the venerable 8-bit 8051 microprocessor. The CH552 8051 QT Py is a modern twist on a vintage processor core. It has many IO options, runs at 16 MHz, and is ultra-compact.

While the QT Py might look like (just another) cute board from Adafruit, it has an intriguing microcontroller choice. The WinChipHead (WCH) CH552 has an E8051 Core. The 8051 is an eight-bit processor that has been around since the 1980s and is still in active use today! WCH's chip contains 16 kilobytes of flash memory but only about 1.25 kilobytes of RAM. The QT Py uses the CH552's internal 16 MHz oscillator and built-in USB physical interface (PHY).

The CH552 QT Py is not just a tiny board. It's a versatile tool that follows the tiny Seeed Studio Xiao form factor, measuring only 20 by 17.5 millimeters! This thumb-sized package contains a microcontroller with various connectivity and usability features. For example, the USB-C interface for programming and the RGB NeoPixel LED for visual feedback enables you to explore this infamous microprocessor core. The QT Py's 10 GPIO pins with castellated edges offer flexibility in soldering header pins or attaching directly to a circuit board.

It's worth noting that the CH552 has some specific programming requirements. For instance, it doesn't support MicroPython or CircuitPython. If you plan to use the Arduino IDE, you'll need to use the ch55xduino board support package, which has a limited-feature compiler. This limit means that not all Arduino libraries are compatible with the CH552, so it's advisable to test example code before committing to a project.

Check out this project from Toby Chui, an example of building a device around the CH552. It is a hotplate that uses a ceramic element for the heater. Chui programmed a CH552 to control the heating profile.

Even though this form factor only exposes 10 GPIO pins, they have considerable flexibility. For example, the 10 GPIO pins support hardware-based I2C, SPI, PWM, and UART interfaces. Four of the pins support 8-bit analog inputs. You can even use those analog inputs as capacitive touch sensors. The CH552 has a built-in voltage regulator that operates up to 5 volts. However, it only supports 3.3 volt IO. The STEMMA QT connector lets you connect to various I2C-based peripherals like sensors.

Adafruit sells the adorable CH552 8051 QT Py at an equally attractive price of $4.95. It is available now, so you can start exploring its unique features and capabilities.

James Lewis
Electronics enthusiast, Bald Engineer, and freelance content creator. AddOhms on YouTube. KN6FGY.
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