Looking for to make a singular impression throughout a current job search, embedded developer Marian Buschsieweke crafted a PCB enterprise card impressed by the Arduboy. Marian’s PCB Enterprise Card includes a 90-LED matrix, six enter buttons, and an STM32 operating RIOT OS. With its cost-effective design, the enterprise card is visually placing and reusable and demonstrates Buschsieweke’s embedded abilities to potential employers.
All of the digital elements match on one aspect of the printed circuit board. The attention-catching part accommodates 90 surface-mount LEDs configured as a matrix. Six push buttons replicate gamepad controls. Marian’s PCB Enterprise Card has an built-in USB-A connector for energy.
Buschsieweke selected a STMicroelectronics STM32G microcontroller to run the cardboard. It accommodates an Arm Cortex-M0+ core with 8 kilobytes of RAM and 64 kilobytes of Flash. The TSSOP packaging offers 20 pins, of which 13 can be found for GPIO. The enterprise card design divides the IO pins between the LED matrix and the enter buttons.
The microcontroller drives the LED matrix with the Charlieplexing approach. This technique allows controlling numerous units with a comparatively small variety of pins. The trade-off is that it takes a bit extra software program to make the matrix work, and for LEDs, it depends on persistence-of-vision (POV) tips. Regardless of these trade-offs, it’s an efficient approach.
Instance of LEDMon exhibiting Down Arrow (📷: mari-bu.de)
Even the enter buttons make the most of Charlieplexing to preserve pins. Nonetheless, this strategy does introduce a possible difficulty: ghosting. Ghosting happens when a person presses two keys concurrently, inflicting an unpressed ‘ghost’ key to look as if it had been pressed. Buschsieweke’s response to this potential downside is easy: simply ignore it!
Two targets that had been essential to Buschsieweke had been price and reusability. Marian’s PCB Enterprise Card wanted to be cheap sufficient to be given away. One instance of price issues was learn how to energy the circuit. Initially, Buschsieweke thought-about a USB-C port and regulator. Nonetheless, the answer was to create a USB-A port utilizing the PCB. Normal PCBs are 1.6 millimeters and are barely too skinny, so somewhat little bit of solder is critical on the +5V and GND pins of the USB connector.
Buschsieweke’s determination to base the idea on the Arduboy design addresses one other purpose: reusability. Customers can proceed enjoying video games that include Marian’s PCB Enterprise Card, develop new ones, or use your complete board to find out about a real-time working system (RTOS).
Marian’s PCB Enterprise Card runs RIOT OS. RIOT is an open sourced RTOS specializing in IoT units. Buschsieweke selected it as a result of its modular construct system based mostly on exterior modules effectively makes use of the restricted reminiscence in IoT microcontrollers. (And since Buschsieweke is a maintainer of the venture!)
There are two video games presently accessible. LEDMon is a “Simon Says” clone. The LED matrix shows a sequence of keys that you simply repeat. The opposite is Flappy LED, a clone of the cellular sport Flappy Birds. Sooner or later, Buschsieweke hopes to enhance the LED matrix code and add traditional bitmap video games like Tetris or Snake. Sadly, we’re dissatisfied to report that there aren’t any plans to port Doom… presently.
KiCad Render (📷: mari-bu.de)
You possibly can obtain the KiCad design information and code from Marian’s PCB Enterprise Card’s GitHub Repository. For particulars on the {hardware} and software program design, try Buschsieweke’s in-depth weblog publish.