ISM330DHCX temperature reading?

[pedro_uno]

Hello,

We have the ISM330DHCX designed into a new product but I am having trouble getting reliable readings using the I2C interface. I am able to read the WHOAMI register and get 0x6B but OUT_TEMP_L (20h), OUT_TEMP_H (21h) always return zero.

I have the interface instrumented and I can see that the signalling is correct, with repeated start and everything, but only zeros.

Does anyone have a suggestion of how this is happening?  Do I need to do something special to enable temperature readings?

Thanks

[Peter BENSCH]

Welcome @pedro_uno, to the community!

Please check STATUS_REG.TDA.

The temperature sensor does not need a special enable sequence, but OUT_TEMP_L/H will only update once valid temperature data is available. Also make sure:

• CTRL4_C.I2C_disable = 0
• CTRL9_XL.DEVICE_CONF = 1
• you wait after power-up/reset before reading, e.g. 1ms

If TDA = 0, the temperature registers may still read as zero.

Hope that helps?

Regards
/Peter

[pedro_uno]

For now I have the processor in a loop that reads the ISM330DHCX once per second. 

You can see that I succeed to read the WHOAMI register. 

STATUS_REG always returns 0x00, TDA not true. 

I read back the CTRL9_XL register and it says I have the DEVICE_CONF bit set.

I2C is enabled by default and I am using I2C to access these registers.  

What else can prevent the part from reporting temperature?

whilecount: 58
gyro_whoami = 0x6B
gyro status = 0x00
CTRL9_XL = 0x02
gyro_temperature = 0x0000
gyro_temperature = 25.000

whilecount: 59
gyro_whoami = 0x6B
gyro status = 0x00
CTRL9_XL = 0x02
gyro_temperature = 0x0000
gyro_temperature = 25.000

[Federica Bossi · Accepted solution]

Hi @pedro_uno ,

Your I2C interface is working correctly since you can read the WHOAMI register.

The ISM330DHCX temperature sensor output registers (OUT_TEMP_L/H) will return zero unless the accelerometer or gyroscope is enabled (ODR ≠ power-down).

Set the ODR of either sensor to a valid value, wait for the sensor to update, and then read the temperature registers.