Jonathan Broadwell's Latest Serial Wombat Offers a Wealth of Features Over I2C — for Just $1.50
Whatever your project needs, the Serial Wombat 8B can probably offer it — all offloaded to an on-board microcontroller over I2C.
Maker Jonathan Broadwell, creator of the Serial Wombat family, is back with another board design — this time the Serial Wombat 8B (SW8B), an input/output expansion board that adds a wealth of features to any I2C-compatible microcontroller or microprocessor host for just $1.50.
"The Serial Wombat 8B is an I2C peripheral that provides smart I/O expansion to solve common interfacing problems — ADC [Analog to Digital Converter], PWM [Pulse-Width Modulation], servo, GPIO [General-Purpose Input/Output], rotary encoder reading, H-bridge interfacing, and more," Broadwell explains. "It has a separate microcontroller that can offload annoying or interrupt intensive I/O tasks from your main board. It's open-source firmware running on an inexpensive [WCH Electronics] CH32V003 microcontroller. The hardware designs are open-source hardware."
The latest in the growing Serial Wombat family, the SW8B is based around the WCH CH32V003 RISC-V microcontroller famed for its impressive capabilities at an extremely low cost. Those capabilities are used to the full in Broadwell's design, which is a breadboard-friendly design with a pre-programmed firmware made to cover a broad range of use-cases — all features of which are available on all pins, and simply activated by the host over an I2C connection.
These features are, in full: a 10-bit analog to digital converter with filtering, averaging, outlier exclusion, linear scaling, and synchronous queuing features; a 17µs-resolution pulse-width modulation output; an H-bridge controller, which combines two PWM outputs into one; a servo controller with rate-of-change control and a resolution "comparable to Arduino UNO servo control," Broadwell promises; proportional-integral-derivative (PID) and hysteresis control mode running on-chip; quadrature and rotary encoder input; pulse timer input; matrix keypad decoding; I2C to UART bridge; TM1637-based seven-segment LED control; and offloaded button debouncing. More features are to come in future firmware updates, Broadwell promises, including stepper motor control, radio-control PPM input, and infrared remote decoding.
In short, the Serial Wombat 8B is a tiny multitool that can be used to work around a lack of features in a particular microcontroller or microprocessor, to expand on existing features, or to offload work in order to free up the host for other tasks. Libraries are included for Arduino C++, Python and MicroPython, and C#, while Broadwell's own "Wombat Panel" software provides an accessible interface for experimentation and can auto-generate Arduino-compatible code.
Broadwell is funding production of the Serial Wombat 8B on Kickstarter, with rewards starting at $10 for a five-pack and dropping under a target $1.50-per-board retail price in higher volume; the maker has also unveiled other board designs based on the same chip and firmware, including the SW8B "Backpack Board", SW8B "Grip" robotics board, SW8B "Bridge" motor controller board, and the SW8B "Crazy8" — eight SW8Bs in one, providing 64 "smart pins" on a single board. "I don't think there's anything out there like this," Broadwell says of this latter design.
All hardware is expected to ship in August this year, Broadwell says.
