BME680 Air quality Values

[kefom]

I am trying to work with Bme680 with I2C communication i can read every value but i cant read air quality value its  always at 806516 value and does not change . I thing configirations are wrong but i got them from bosch site so i dont know what to do if anyone can help i would be glad .

these are my settings

{
uint8_t set_required_settings;
/* Set the temperature, pressure and humidity settings */
gas_sensor.tph_sett.os_hum = BME680_OS_2X;
gas_sensor.tph_sett.os_pres = BME680_OS_4X;
gas_sensor.tph_sett.os_temp = BME680_OS_8X;
gas_sensor.tph_sett.filter = BME680_FILTER_SIZE_3;
/* Set the remaining gas sensor settings and link the heating profile */
gas_sensor.gas_sett.run_gas = BME680_ENABLE_GAS_MEAS;
/* Create a ramp heat waveform in 3 steps */
gas_sensor.gas_sett.heatr_temp = 320; /* degree Celsius */
gas_sensor.gas_sett.heatr_dur = 150; /* milliseconds */
/* Select the power mode */
/* Must be set before writing the sensor configuration */
gas_sensor.power_mode = BME680_FORCED_MODE;
/* Set the required sensor settings needed */
set_required_settings = BME680_OST_SEL | BME680_OSP_SEL | BME680_OSH_SEL | BME680_FILTER_SEL
| BME680_GAS_SENSOR_SEL;
/* Set the desired sensor configuration */
rslt = bme680_set_sensor_settings(set_required_settings,&gas_sensor);
/* Set the power mode */
rslt = bme680_set_sensor_mode(&gas_sensor);
}

this s the code that i use to get data 

nrf_delay_ms(meas_period);
rslt = bme680_get_sensor_data(&data, &gas_sensor);



if (gas_sensor.power_mode == BME680_FORCED_MODE)
{
rslt = bme680_set_sensor_mode(&gas_sensor);

}

Best Regards 

Efe

[Nguyen Hoan Hoang]

See the driver and example code here.

Driver : github.com/.../tphg_bme680.cpp

Use case example : https://github.com/IOsonata/IOsonata/blob/master/exemples/sensor/env_tph_demo.cpp

to get the Air Quality Index, you need to pass the data read from the sensor to the BSEC library to do the conversion.   They don't give you the details equation to convert from gas resistance value to AQI. 

[kefom]

i couldnt understand but i will try what you said . But i want to make this clear the value i get from reading data from sensor for gas resistance does not change . The value changing is normal or not ? 

[Nguyen Hoan Hoang]

The values should varies. 2 things could happen when you get fixed value.  Either the code is not correct or the sensor is effective.  Try with another board.  If you get the same result, it likely the code issue.  The BME680 is a sensitive device.  If it get cleaned in liquid (water or flux cleaner) after assembly, the sensor is likely be effective after cleaning.  

[kefom]

thanks for your fast answers it means a lot to me. I want to ask if you know the reason might be this ?

i am writing 140 data to temp , hum and press registers and they work but i am not writing and additional data to gas_resistance part ( i cant find that register in datasheet ) i belive the reason is my code but i will also try to clean the sensor too.

uint8_t data[1]={140};
uint8_t reg[1]={0x74};
uint8_t rega[1]={0x72};
uint8_t regs[1]={0x73};
//uint8_t regg[1]={0x75};
bme680_set_regs(reg, data, 1, &gas_sensor);
bme680_set_regs(rega, data, 1, &gas_sensor);
bme680_set_regs(regs, data, 1, &gas_sensor);
//bme680_set_regs(regg, data, 1, &gas_sensor);
nrf_delay_ms(500);

while (1)
{
uint16_t meas_period;
bme680_get_profile_dur(&meas_period, &gas_sensor);

struct bme680_field_data data;

after writing to these registers i just write 

if(data.status & BME680_GASM_VALID_MSK)
            printf(", G: %d ohms", data.gas_resistance);
if (gas_sensor.power_mode == BME680_FORCED_MODE)
{
rslt = bme680_set_sensor_mode(&gas_sensor);

}

this to the end of the code for gas_resistance

Best regards Thanks 

Efe

[Nguyen Hoan Hoang]

What I meant about cleaning is actually do not clean it. If any liquid gets into the little holes on the sensor, it will destroy it. Be careful with that.

[kefom]

yes i know you didnt mean that i tough maybe some dust entered in it so i was just ganna blow it with air thanks tough for the warning i am thankfull

[Nguyen Hoan Hoang]

for the code, there are some initialization that need to be performed before reading the resistance value.  One of which is the setting of heating profile.  Look for the function 

bool TphgBme680::Init(const GASSENSOR_CFG &CfgData, DeviceIntrf *pIntrf, Timer *pTimer)

In the code I showed you previously via the link to github.  I am not using the bosch driver but they should have something equivalent. 

Another example code where see how the IOsonata driver work.  This one reads the sensor including the AQI and sends them over BLE Advertisement data.

https://github.com/IOsonata/IOsonata/blob/master/ARM/Nordic/exemples/TPHSensorTag.cpp

This blog describes about it but its a bit old now https://embeddedsoftdev.blogspot.com/2018/01/

[kefom]

Thanks you have been really helpfull i will look into this function and settings , the links .thanks again for the answers 

Best regards.:)