Led Panel Pax Indicator

This morning I was seized with a desire to make an indicator for the PAX counter device that I’ve been playing with. The counter sends the number of WiFi and Bluetooth devices that it has seen in the last minute up to The Things Network via Lora and I fancied making something that displayed that number.

A while back I had a play with a LED panel that looks rather nice. In fact I’ve got one stuck on my wall and I bought a few more at the time. So I got one out of the garage and set about getting it to work.

Last time I used a Teensy device but this time I thought I’d use one of the dirt cheap ESP32 devices that I’ve bought a few of. The hardware of the panels is actually quite simple. There are connections for red, green and blue (RGB) pixels and you just shift the pattern for row of pixels into these connections. There are four address bits you can use to select which of 16 rows you wish to control, and there are two RGB inputs, so you can drive two rows at the same time.

I used the library here to drive the panels from my ESP32. The panels are designed to be daisy chained so that you can send a row of pixels that spans a number of them. The library uses this to good effect by linking the outputs back to inputs so that all the colours can be regarded as one great big shift register. This reduces the number of pins that you need to allocate to drive the display, at the expense of a bit more wiring.

I’ve used what I call a “spatchcock” assembly method. Because the ESP32 is supplied with soldered pins I’ve had to solder onto these pins and then flatten them so that the device will fit inside the picture frame.

I’ve got it displaying pictures. Tomorrow I’ll try drawing some text.