This is test firmware for controlling a shitload of 14-segment LED modules:
Adafruit offers a board that drives four digits, based on the HT16K33 LED driver chip, which is quite old and now discontinued. It also doesn't support a lot of addresses with I2C.
I wanted to drive a LOT more digits, and ended up using the more modern IS31FL3737 LED driver around a custom PCB. It supports individual segment dimming and many more I2C ddresses.
I am using an ESP32 to develop this ongoing project with the eventual goal to build a massive 80x24 terminal using these LED modules (around 1 meter wide).
There's no clear standard for how 14-segment digits are wired. The LED driver supports 16 common cathode lines and 12 sinks. This project is based around the 5321AS 0.54" 2-digit 14-seg module, which is usually available on AliExpress for less than $0.40 per component. It has 18 pins in total with decimal places.
In this application, the module pinouts are shown in the following sequence:
The PCB supports different I2C addresses, set with solder jumpers. So with a single I2C connection you can control 16x12 digits, or 192 characters. And they could be tiled by using multiple controllers or some kind of I2C multiplexing.
After building the rev1 prototype (see below), it was clear there were too many connection points for wires and screws to deal with. I re-designed the PCB to include four drivers, arranged in a 16 column x 3 line layout. I also added JST PH 2.0 connectors for I2C and power, with a TI level shifter/buffer to handle I2C. This prototype was working well. (July 2024)
And a special board to distribute power and I2C connections to 8x modules.
In the first rev, each PCB had 12 digits and a single LED driver. This worked, but was a bit of a pain to assemble. (January 2024)
