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Original question:

INA229: Device sends invalid data on MISO until INA229 is power cycled.

INA229_239EVM: Unexpected behavior with chip select

Boris
Prodigy 20 points
Part Number: INA229

Hello,

Background:
I am using a single INA229EVM connected to an STM32 dev board via the J2 connector. I am not using the SCB / PAMB controllers.

Issue: 
When connecting the CS line to the EVM board and selecting the appropriate CS (CS1-4) via the switch, the INA229 stops responding on MISO. All examples below show Device ID command as example.

Case 1: Connecting CS to the CS4 input on J2, then selecting CS4 via SW1 switch causes INA229 to stop responding on MISO



Case 2: Connecting GROUND to the CS4 input on J2, then selecting CS4 via SW1 switch causes INA229 to stop responding on MISO




Case 3: Connecting CS to the CS1 input on J2, then selecting CS4 via SW1 switch causes:
- INA229 to successfully respond with 0x2291
- When probing CS on the INA229EVM it is 0V
- Note: In the logic analyzer trace below, CS is probed at the output of the STM32, not input to INA229. At INA229 it is sensed as 0V.



I am quite confused by what is happening here and why in Case 3 the INA229 seems to respond fine even though both in Case 2 and 3 the CS seems to be 0V. Any help understanding what's happening here would be helpful. Thank you!

  • 0
    TI__Expert 6602 points

    Hi Boris,

    For the cases not working, can you measure the chip select voltage on the CS pin of the INA229 with respect to the GND pin of the INA229?

    Best,
    Mohamed 

  • 0 in reply to Mohamed Hamida
    Prodigy 20 points

    Hi Mohamed,

    I've attached an oscilloscope trace and logic analyzer trace when CS1 is used (connected to main micro + selected on switch). CS line looks right to me as it goes active low before SPI clock is enabled and goes high (3.3V) when SPI transaction is complete. No data is seen on MISO line.

    I have also verified continuity of CS line all the way from STM32 micro to INA229 CS pin, and same for grounds.

    Trace 1: Oscilloscope trace showing Device ID command sent with no response back.


    Trace 2: Logic analyzer trace showing Device ID command sent with no response back.


    Thanks,
    Boris

  • 0 in reply to Boris
    TI__Expert 6602 points

    Hi Boris,

    This is quite strange. Do you mind sending me picture of the physical setup as well as how the STM32 is interfacing with the IN229? Seeing the J2 connection should give me a better view of what's going on. Also, is there any other relevant information you could share that would help me decipher what's going on?