Debug ESP32/ESP8266 programs in PlatformIO using the exception decoder

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This is the prototype. I think I need to make a PCB for this..

I’ve been hard at work adding RFID abilities to Connected Little Boxes. It’s going mostly OK. It worked first time, which I hate because it means that the pain comes later. And it did, in the form of random crashes. The program would run for a while and then reset with an exception. The ESP devices produce a lump of debug output when they fail, but you then have to decode this text. The great news is that this behaviour is built into PlatformIO, the wonderful tool that I’m using to make the application. All you have to do is add the following line to the platformio.ini file in your project:

monitor_filters = esp8266_exception_decoder

The serial monitor will now look for the messages that mark the start of the debug information and then use the build file to tell you where the program was when it fell over. Very useful. In my case it allowed me to determine that the program was failing in WiFi code, not something that I wrote. Of course, even though it is not failing in my code, I still have to fix it. I have two golden rules when debugging embedded code:

  1. First check the power supply.

  2. Second check the memory allocation.

In this case the power is OK, so the problem must be memory. I thought I had enough free memory for the system keep going but this turned out not to be the case. I freed up a bunch of space and the device has been running solidly ever since.