BME688 not giving gas readings

[boydy]

Hi

I am developing a lightweight sensor board which contains the BME688.

I am looking to implement the forced read mode, and have written code that I believe reflects the quick start.

I am using the sensor with SPI and can communicate with the device, and am writing the code as a bare metal implementation in C.

I am also able to read back any register value, and am getting values for temp, pressure and humidity - but nothing for gas resistance.

The gas_r_lsb register is reporting 0x04, which suggests that the device has not achieved the heating current - yet no changes of times or target currents seem to change this.

I have read back the registers in the device, and they all appear to be as expected. I have also observed that the current draw from the device does inrease if the heating time is increased, as I can see the linear device that powers it warm up by a few degrees with a thermal camera when the time is extended.

As an experiment I also switched the device into paralell mode, but this made no difference to the output.

What am I missing?

Ta!

[BSTRobin]

Hello boydy,

According your description, suggest you use BSEC1 for your reference, BSEC1 package contained BME68X driver code, BSEC library, integration guide. You could download it from here: https://www.bosch-sensortec.com/software-tools/software/bsec/

[boydy]

Hi BSTRobin (we share a first name :-))

I have just downloaded the BSEC package, and I'm not sure I can make it work - I am using a PIC processor in my application, which is not supported by the pre-compiled library.

I note a comment about the supply voltage requiring a compensation for the self heating - I am running at 1.8v on my board, do I need to change the calculation for the target heater current?

Thanks!

[boydy]

I am still struggling to get any sense out of this, is there any more information available?

Thanks!

[BSTRobin]

Hello boydy,

You could check the following supported platform document to see if you host MCU could compile BSEC library.
https://www.bosch-sensortec.com/media/boschsensortec/downloads/bsec/bsec1_binary_size_information.pd...

If your host MCU and compiler didn't match the document list. you could visit https://www.bosch-sensortec.com/about-us/contact/contact-form, and use the contact form to submit your application.

From BSEC integration guide, 1.8V was also supported.