sensirion / arduino-snippets Goto Github PK

Line 63 in SCD4x_I2C_FRC_Forced_Recalibration_Example.ino causes an integer overflow:
delay(5 * 60 * 1000);
In an Arduino Uno and other ATmega based boards the maximum value for an int is 32,767. Consequently, 5 * 60 * 1000 gets evaluated to a negative number and the delay never terminates.
Possible solution:
delay(5 * 60 * (long)1000);

I'm not super familiar with Arduino code and I'm trying to figure out if the forced recalibration SCD4x snippet is something I can just run once, then switch back to the usual periodic measurement script provided in the tutorial I followed. Will the calibration persist? If not, how can I edit the re-calibration code to turn this feature on?

Hi,
I found that your code "SCD4x_I2C_FRC_Forced_Recalibration_Example.ino" was not working properly.
Instead of waiting for the sensor to startup and equalize itself to ambient levels, it started the calibration directly after powerup.

I found that at line 99, the delay was commented.

97 // wait for another 5 minutes to equilibrate sensor to ambient
98 Serial.println("# Waiting 5 minutes for equilibration");
99 //delay(5 * 60 * 1000);

I uncommented this delay, but also moved it up to line 60. This was because the values used as "CO2 values before recalibration" (lines 66-76) where saved before the initial equilibration delay at line 99.

Could you confirm this?
After I made the changes, sensorreadings where as expected from ~400PPM co2 levels in the outside ambient air.