CO2 Sensor Senseair S8 - big values read

[wasssu]

Hi,

I installed a Senseair S8 senzor on a Raspberry Pi 4. In the first week it worked ok (values coming close to 400 ppm when I open the window) then it started to show big values, especially when I open the window, values like 65429 ppm. The reading interval is 15 seconds. I use this code to get the value from the sensor. Any idea what could be the problem?

    ser = serial.Serial("/dev/serial0",baudrate =9600,timeout = .5)
    ser.flushInput()
    time.sleep(1)
    ser.flushInput()
    ser.write(b"\xFE\x44\x00\x08\x02\x9F\x25")
    time.sleep(.5)
    resp = ser.read(7)
    high = resp[3]
    low = resp[4]
    co2 = (high*256) + low

Thanks!

[mfalkvidd]

Welcome to the forum @wasssu

Best way to find out is probably to log the contents of the resp variable.

[epierre]

maybe check what they did here:
https://github.com/airgradienthq/arduino/blob/master/AirGradient.cpp