NeoPill Is an STM32-Powered NeoPixel Emulator

NeoPixels are great for custom lighting solutions for any number of projects, but they can be a hassle when it comes to testing different pixel patterns. Experimenting with different patterns on NeoPixels strips can be time-consuming for testing, as each change requires recompiling and reuploading the software. To that end, electronics enthusiast Randy Elwin has developed a way for users to make changes to their NeoPixel patterns and port them over in a fraction of the time. It also lets them quickly add up to 1000 NeoPixels to their projects while still changing custom patterns.

To get around that time-consuming testing issue, Elwin created an emulator that enables users to program and test their designs on a PC, then upload the changes to the NeoPixels. He created the NeoPill – a “USB bridge” of sorts designed around an STM32 Blue Pill microcontroller, a few jumpers, and a USB cable to connect the LEDs to the PC.

“NeoPill converts the NeoPixel serial data into bytes and sends those bytes to a PC over USB,” Elwin states in his project blog. “However, NeoPixel data is always written as a frame, where all the LEDs in a string are written, followed by a short pause called Data Latch. When the code running on the PC is ready for pixel data, it expects to be synced with a frame. Once synced, the pixel data streams out, and there is no other syncing involved.”

Elwin created the emulation code using Python, and while the NeoPixel library uses C++, he managed to port most functions from the library to the emulator. This allows users to copy and paste code back and forth from both platforms. Elwin has uploaded a detailed walkthrough of the NeoPill, including the necessary code, on his project page for anyone who would like to recreate his build.