ESP8266 NodeMCU running out of heap

Using Arduino Programming Questions
#1

Hello,

I'm trying to create SMS alarm using Twilio, Firebase and Arduino IDE. Using sensors I am measuring the temperature. If the temperature is higher than a specified value (ESP reads that value from Firebase Realtime Database), a SMS should be sent using twilio. I am also storing the measures in Firebase Realtime Database. The code worked well, until I tried to retrieve data from Firebase one more time and set data two more times. I believe that I'm running out of heap. I have only 10k heap left and cannot send SMS via Twilio. It only prints: connecting to api.twilio.com, but I don't receive the message.

I deallocate the Firebase Data objects after every loop, however, I believe, I still don't have enough heap. Do you have any suggestions how to optimize the code and gain more memory?

I posted the same question with code included on StackOverflow (https://stackoverflow.com/questions/64067911/esp8266-nodemcu-running-out-of-heap) because it exceeds the maximum allowed length on Arduino Forum.

Any help would be appreciated!

#2

Please post your code according to forum rules. Some people will not go to another website to access the code.

#3

The highest probability for youcode running out of heap-memory is global defined variables of type String.
The Arduino-Crew added the variable-type String to the core but this is of a highly doubtful benefit.

Global defined Strings eat up memory over time. There are two main alternatives:

  1. only use variable-type String inside functions that get called in a regular manner.
    variables defined inside functions don't use heap-memory

  2. replace all variables of type String with c_string, array of char or PString.

anyway for analysing your code post your code in code-tags

best regards Stefan

#4