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Original question:

INA233: I2C Data and Clock Lines Held

INA233: Power Calculation I2C Problems

Shaun Linkogel
Prodigy 40 points
Part Number: INA233

Hello, 

So I am having i2c issues linked to the INA233 where once we enable a brake motor the i2c communication fails. After some investigating we commented out getting the power value from the INA233 in our code. We are able to read the voltage values and the current values from the INA233 just fine with the power commented out and the I2C does not lock up. The clock line is held high and the data line is held low on the last bit of the transmission. The last byte where the transmission gets locked up is consistently on the INA in which the motor is engaged. Is there something that is going on with the power calculation in the INA233 that would cause the INA233 itself to hold the line? I understand that the INA233 makes the current and power calculation based on the vshunt differential voltage. Maybe we have calibrated the INA233 incorrectly. Any thoughts on this problem would be appreciated.  

  • 0
    TI__Expert 6602 points

    Hi Shaun,

    Can you give me some more information on the parameters you set in the calibration and configuration registers for the INA233? This would help troubleshoot the issue. Also, the power calculations are based on the VBUS voltage. 

  • 0 in reply to Mohamed Hamida
    Prodigy 40 points

    Hello Mohamed, 

    I calculated the Current_LSB to be (525mA/2^15) which gave us the value 0.0000160217. The maximum expected current for our motors is around 503mA. Then, I figured the Calibration value to be (0.00512)/(0.0000160217*0.039) from that value. (0.039 is the value of the shunt resistor that was used) This gave us a Calibration value to be 8194. 

    We also configured the MFR_ADC_CONFIG register to be 0x4577 which gives us 16 averages, 2.116ms on the VBUS conversion, 4.156ms on the Vshunt conversion, and then set to shunt and bus continuous operating mode. 

    The registers that we are reading from are 89h READ_VIN and 97h READ_PIN. 

    Hopefully, that gives a better idea of how we configured the INA233. 

  • 0 in reply to Shaun Linkogel
    TI__Expert 6602 points

    Hi Shaun,

    The calibration looks fine. It may be worth reading registers in a different order to see if it is actually the power register, or if its simply the order that is messing things up. Another thing to look into would be noise levels. It could merely be a coincidence that it works when the power register is being commented out. Using a scope to read noise levels may help. Could I have some more information on the I2C bus and its addresses? Also, can I have the register values of the current and voltage registers as well as the VBUS register? This would help back-calculate the power register for confirmation.