CO2 Readings Stop Until Hard Restart (S8 Sensor Shutdown)

[macserv]

I have two AirGradientOne I-9PSL units (pre-soldered kits, purchased at the same time). Both devices, after an indeterminate length of time, will stop reporting a CO2 reading until restarted with a full power cycle.

Note

I'm new to embedded device programming, but not to software development in general, so if someone can walk me through how to debug the code running on the device (or point me to a good tutorial), I'd be happy to dig deeper. A quick search suggests I might need additional (JTAG) hardware, but if it can be done over the USB connection, I'll give it a shot.

Troubleshooting Notes

• Captured log output in several scenarios... see "Serial Monitor Output" below.
• Tried several USB cables and power adapters (including the direct connection to computer while monitoring) with no discernible change to behavior.
• A soft reset is not sufficient to restore normal operation; the power must be cycled (i.e., disconnect and reconnect the USB cable).
• After cycling the power, the CO2 sensor will function normally again for an indeterminate length of time, but the issue will always recur.

Serial Monitor Output

Normal Operation

When functioning normally, the serial monitor output shows valid responses from the S8.

[125681][I][S8.cpp:757] validResponse(): Valid response
[125752][I][S8.cpp:244] getCo2(): CO2 value = 866 ppm
[125926][I][Sgp41.cpp:339] setCompensationTemperatureHumidity(): Update: defaultT: 25367, defaultRh: 31480

CO2 = 866.00 ppm
Temperature = 22.74 C
Relative Humidity = 48.06
...

Malfunction

When the device stops reporting CO2 readings, the serial monitor output indicates invalid responses from the S8.

[23941108][I][S8.cpp:786] validResponseLenght(): Err: Unexpected length!
[23941196][I][S8.cpp:339] getCalibPeriodABC(): Error getting ABC period!
[23942459][I][S8.cpp:786] validResponseLenght(): Err: Unexpected length!
[23942547][I][S8.cpp:246] getCo2(): Error getting CO2 value!
CO2{1} invalid value update counter reached (3x)! Setting its average value to invalid!
[23942728][I][Sgp41.cpp:339] setCompensationTemperatureHumidity(): Update: defaultT: 24771, defaultRh: 32197
Last process timeout, clear buffer and last handle package

CO2 = -
Temperature = 21.16 C
Relative Humidity = 49.13
...

Warm Reset

If I use the PlatformIO "Upload and Monitor" task in to restart the device without cycling the power, the monitor output indicates that the S8 is not found.

[  7297][I][S8.cpp:659] init(): Init on 'Serialx'
[  7302][V][esp32-hal-uart.c:330] uartBegin(): UART1 baud(9600) Mode(800001c) rxPin(0) txPin(1)
[  7312][V][esp32-hal-uart.c:416] uartBegin(): UART1 not installed. Starting installation
[  7321][V][esp32-hal-uart.c:467] uartBegin(): UART1 initialization done.
[ 12437][I][S8.cpp:786] validResponseLenght(): Err: Unexpected length!
[ 12445][I][S8.cpp:96] getFirmwareVersion(): Firmware version not available!
CO2 S8 sensor not found
...
[StateMachine] Warning: CO2 S8 not available, set 'abcDays' ignored
HTTP domain name from configuration empty, set to default
[ 54468][I][Sgp41.cpp:339] setCompensationTemperatureHumidity(): Update: defaultT: 25108, defaultRh: 32959

Temperature = 22.03 C
Relative Humidity = 50.30
...

Cold Reset

If I disconnect and reconnect the USB cable, the S8 begins functioning again:

[  7302][I][S8.cpp:659] init(): Init on 'Serialx'
[  7307][V][esp32-hal-uart.c:330] uartBegin(): UART1 baud(9600) Mode(800001c) rxPin(0) txPin(1)
[  7317][V][esp32-hal-uart.c:416] uartBegin(): UART1 not installed. Starting installation
[  7326][V][esp32-hal-uart.c:467] uartBegin(): UART1 initialization done.
[  7455][I][S8.cpp:757] validResponse(): Valid response
[  7461][I][S8.cpp:94] getFirmwareVersion(): Firmware version: 1.2
[  7468][I][S8.cpp:679] init(): Firmware version: 1.2
[  7473][I][S8.cpp:681] init(): Sensor successfully initialized. Heating up for 10s
...
[  7964][I][S8.cpp:757] validResponse(): Valid response
[  8035][I][S8.cpp:337] getCalibPeriodABC(): ABC period: 192 hour
Set S8 AbcDays successful
...
[ 44910][I][S8.cpp:757] validResponse(): Valid response
[ 44981][I][S8.cpp:244] getCo2(): CO2 value = 1257 ppm
[ 47221][I][Sgp41.cpp:339] setCompensationTemperatureHumidity(): Update: defaultT: 25214, defaultRh: 32860

CO2 = 1257.50 ppm
Temperature = 22.33 C
Relative Humidity = 50.20
...

[samuelbles07]

Hi @macserv ,

Do you still have this problem after the cold reset? If not, perhaps its relate to this this forum https://forum.airgradient.com/t/all-airgradient-one-sensors-repeatedly-updating-on-3-3-6-starting-09-30-gmt-29-04/4069

[macserv]

Hey, @samuelbles07 ,

Good question! Yes, the issue will always recur after cycling the power. To clarify, I've updated the troubleshooting notes above with the following item:

After cycling the power, the CO2 sensor will function normally again for an indeterminate length of time, but the issue will always recur.

[macserv]

@samuelbles07 @pnt325 @airgradienthq Hey, all, following up after a couple of months... can anyone provide some guidance? Thanks!