You should use an interrupt handler. gpio_isr_handler_add would be a starting point. As the doc says, do the least work you can in the isr handler, update state information and return. Don't call anything. Use an async task to consume the state information. The state information lives in static var...

boarchuz last two suggestions are really good.

Use EMBED_TXTFILES for text files to get a trailing NULL character to terminate the string. Whatever parses the text may depend on the NULL, which is not part of the file's data.

I don't know anything about OBD and CAN bus, but it looks like fun. Lots of links on the web... https://www.seeedstudio.com/OBD-II-CAN-BUS-Development-Kit-p-2993.html https://os.mbed.com/cookbook/OBDII-Can-Bus My reading: the CAN bus must have some signal conversion hardware: ... wires are called CA...

https://www.espressif.com/sites/default ... eet_en.pdf near page 20 has power-on-reset info.

I am not a hardware expert. I think this might have some good ideas about power-on reset circuits.
https://www.maximintegrated.com/en/desi ... /3227.html

Thanks @mbratch! I studied some more and now understand my case. The document "ESP32 Series Datasheet" page 62, appendix A, "IO Mux" describes pins after reset, some not enabled, some Input enabled, and if input enabled with a weak pull up, pull down, or neither. The weak pull up and weak pull down ...

https://randomnerdtutorials.com/esp32-p ... nce-gpios/ does show a pwm signal during boot on several pins for some device. That is consistent with my experience too. I live with it; it makes an unusual 7-seg display until the boot is finished. I wish I'd rearranged the pinout to hide it.

https://arduinojson.org/
has the details on parsing the JSON

All the top google hits seem to use ArduinoJSON library. https://randomnerdtutorials.com/decoding-and-encoding-json-with-arduino-or-esp8266/ https://www.learnrobotics.org/blog/parse-json-data-arduino/ The data you have, 1,2,3,4,5 is binary. JSON is a way to package the binary data as a printable str...