Case for EX-DCCInspector (Heltec ESP32)

thingiverse

This is a remake of a box I designed a couple of years ago to hold a Heltec ESP32 Development Board for use as a model railway diagnostic tool, analysing the quality of the DCC signal on the tracks. The Heltec module has an ESP32 controller with WiFi, 128x64 8-line OLED display, LiPo battery regulator and charger, and two buttons (one of which is the reset button). In my application, there is an opto-isolator input circuit on a small piece of stripboard, to isolate the track voltage from the internals of the device - this circuit is accommodated in a separate partition of the box to the ESP32, and the output of the opto-isolator is connected to an input pin on the ESP32. I've provided for a power switch (SPDT mini slide switch) in line with one of the battery leads, so it doesn't run down when not in use. It's not ideal as it won't charge either, unless it's switched on, so if someone can suggest a better way to connect it I'm mostly ears. The software I wrote for this can be found by searching for EX-DCCInspector. This software samples the DCC waveform at high accuracy (<1us) and reports on the quality of the signal, i.e. how accurate it is relative to the DCC specifications. It also decodes and displays the DCC packets it captures from the track, locally on the OLED display. To get the best use out of the eight lines available on the screen, you can scroll a screenful at a time by using the uppermost of the two buttons. You can also connect a laptop or other computer, and by using terminal software (e.g. puTTY or the Arduino IDE's Serial Monitor) the information can be displayed on the computer. Lastly, the device, on power-up, searches for a WPS-enabled router and if it finds one, connects to it. This allows you to access the diagnostic information over WiFi by connecting directly to the device using a Web Browser, at address `http://dccinspector.local`.