bme680_dev.amb_temp is an input for the gas sensor configuration. It is possible to keep a hard-coded, for example at 25.
bme680_field_data.temperature is the output of BME680's temperature sensor measurement. To support some decimal points, the resolution of the integer formula output is 100LSB/°C, while the floating-point formula outputs directly in °C. It is recommend to use the floating-point implementation if your platform supports it.
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