bme688 saturation to 102400000.0 on low gas heater temperatures

[zrummler]

With the bme68x.h sensor API, the gas resistance value occasionally saturates to 102400000.0 and this doesn't seem correct. This really only happens for lower temperatures in the heater profile (say 100C, as opposed to 150C or above)

I ran some debugging and here's what I know:

1. The gas resistance value is calculated using two inputs, gas_res_adc and gas_range. The calculation is 102400000.0 when both of these inputs are 0. (They shouldn't ever be 0).
2. These values come from registers gas_adc and gas_range, at addresses x2C and x2D. It appears that often times when I read these registers, they store 0. This is the case even when the status bits BME68X_NEW_DATA_MSK, BME68X_GASM_VALID_MSK, BME68X_HEAT_STAB_MSK are TRUE.

So it seems that the gas_adc and gas_range registers often hold no data even when the status bits indicate that there should be data there. This only happens for lower temperatures of the gas heater profile. I cannot figure out why this could be. Anyone seen this before?

I am not using BSEC or the Development Kit, I am just using the source code API from GitHub: https://github.com/BoschSensortec/BME68x-Sensor-API/blob/master/bme68x.h

[BSTRobin]

Hi zrummler,

The sensor is saturated or not within the operating range specified in the specification when resistance 102400000.0 ohms is typically present. What is your test temperature? What is your testing environment?

[zrummler]

I'm indoors (at my office cubicle) at room temperature.

[BSTRobin]

Hi zrummler,

You can run the sensor API and example code of BME688 and use the standard heater profile to observe the changes in gas resistance values.