ESP32 internal_temperature component - difference option

[anzejarni]

Describe the problem you have/What new integration you would like

Please add an optional 'difference' boolean, that enables the following function:

1. Read the the initial temperature on boot
2. Return the temperature difference between the read temperature and initial temperature

This would be very beneficial to be able to tell if the chip or/and components on the PCB are overheating for some reason.

Please describe your use case for this integration and alternatives you've tried:

I have several operational S2 ESP32 chips. Some reporting the right temperature and others are far off. They all however do have the same increase curve when they start heating up after boot. So the initial read temperature is wrong, however the change seems to be accurate.

Additional context

[anzejarni]

[Unfocused]

As an alternative, this could be done using a custom filter:

sensor: 
  - platform: internal_temperature 
    name: "Internal temperature delta"
    filters: 
      - lambda: !lambda |- 
          // Using static will make this retain it's value between calls
          static float boot_temp = -1;
          if (boot_temp == -1) {
            // Store the value of only the first time
            boot_temp = value;
          }
          // Return the difference between the current temperature and the first temperature after boot 
          return (value - boot_temp);     

(Untested & written on my phone, so please excuse any typos & indentation issues)

[anzejarni]

@Unfocused thanks! Changed your code a bit to work.

sensor: 
  - platform: internal_temperature 
    name: "Internal temperature delta"
    filters: 
      - lambda: !lambda |- 
          // Using static will make this retain it's value between calls
          static float boot_temp = -999;
          if (boot_temp == -999) {
            // Store the value (x) of only the first time
            boot_temp = x;
          }
          // Return the difference between the current temperature and the first temperature after boot 
          return (x - boot_temp);  

But I still think it could be nice to have it integrated into the component if the codeowner has time.

Did some testing and it seems to be pretty accurate. The difference readings are 4 - 10 degrees Celsius above ambient after boards heating up to operating temperature, which given on the locations of installation, seems to be correct. Cooling the room with AC also produces a sensible temperature drop in the differential readings.

[Unfocused]

It could be added as a built-in filter, then it would be availble to all sensors