Serial Communication between Arduino Nano and ESP32 using ArduinoJson

[mrburnette]

Welcome to the Arduino help forum. Thank you for providing your code nicely formatted.

I did a search on your error:

ESP32 + Arduino +"Stack smashing protect failure!"

Within the results returned, I found this thread suggesting "S"tring could be the issue:

how to fix stack smashing protect failure in ESP32

By null-terminated string I mean to use something like: #define MAX_STR_LEN    256 char szNullString[MAX_STR_LEN]; and small-s string functions like sprintf(szNullString, "...) strcat(szNullString, ...) etc to manipulate them. Capital-S String(...) stuff requires a lot of memory and machine cycles. They are generally frowned upon by the Arduinoista because they're known to cause memory problems and crashes in lesser processors. I don't know if the ESP32 & its compilation/linking tools are su…

Personally, I would not use JSON library to move between two microcontrollers; just move a struct, more efficient.
How to send and receive struct data packet over serial - Using Arduino / Programming Questions - Arduino Forum