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DRV8847SEVM: External I2C communication connections

Brian Wang0
Expert 5310 points
Part Number: DRV8847SEVM
Other Parts Discussed in Thread: DRV8847,

Dear team,

One of my customer is trying to simulate I2C with GPIO of C2000 to control DRV8847.

However, we found that if we set F28069 GPIO and then config it as input, the SDA voltage level will become 2V rather than 0, when then ACK signal of DRV8847 arrives.

We believe it is a circuit level problem rather than software. 

My question is: if we try to use GPIO as I2C to control DRV8847 on DRV8847SEVM, do we need to modify the board(change resistor or move jumpers)?

I have connected SDA, SCL, nSLEEP and GND， what else do I need to do?

Can you provide the schematic of this EVM?

Thanks a lot!

  • 0
    TI__Genius 14487 points

    Weiqi,

    I attached the schematic to this message. I am working to have the design files available on TI.com.

    You will also need to remove the resistors associated with those signals from the EVM before you can apply the external signals. For SDA, SCL, and nSLEEP, you need to remove R8, R11, and R12. You may also want to remove R9, R10, R13, and R14 to interface your MCU with the INx pins.

    MD012E2(002)_Sch.PDF

  • 0 in reply to James Lockridge19
    TI__Expert 5310 points

    Hi James,

    I followed your instruction by removing resistor R8 R11 and R12 to isolate the DRV8847 from MSP430.

    However, when I try to test with my c2000, I am never be able to observe a high-level on SDA even I wrote nothing in my program.

    So I tested the SDA and SCL port on the EVM directly without C2000. I connected 12V power supply, USB to provide 3.3V pullup voltage and a 3.3V is connected to nSleep .

    This is what I got:

    Both signal is no more than 1 volts. I believe, if the I2C is functional, both lines should show high level. Does this mean the DRV8847 is damaged?

    BTW, is the program firmed on 430 on this board? If I change a new 430, can the GUI download the new program?

  • 0 in reply to Brian Wang0
    TI__Genius 14487 points
    Weiqi,

    Since you tried driving the MSP430 and the C2000 at the same time, my guess is that the GPIO of the MSP430 may have been destroyed rather than the DRV8847 pins. You may also want to double check the C2000 to see if the GPIO you were using on that device are okay. I think the DRV8847 may be fine because you were likely within the Abs Max values for the device for this condition.

    If you replace the MSP430 on the board, you will need to download the firmware from the EVM page and program it onto the MSP430 using the SPY-BI-WIRE connector (J1) on the board.
  • 0 in reply to James Lockridge19
    TI__Expert 5310 points
    James,
    To make it clear, I am not using the MSP430 since I have removed 0 ohms resistor r8 r11 and r12.
    Please kindly review my question and give your response.
    Thank you!
  • 0 in reply to Brian Wang0
    TI__Genius 14487 points
    Weiqi,

    The SDA and SCL lines are pulled up to the 3V3OUT power net. Can you probe the pullup resistors on the board to ensure that the supply is actually at 3.3 V? If it is 1 V, then you may need to supply 3.3 V from an external supply and disconnect the USB. When you do this, check the current from the supply to see if the board is drawing more than you would expect (>50 mA would concern me).

    Also check your C2000 I2C GPIO to see if you get correct voltages you expect there.

    In the meantime, I would recommend ordering another EVM in case you have damaged the current one.
  • 0 in reply to James Lockridge19
    TI__Genius 14487 points
    Hello Weiqi,

    I believe we are addressing this offline, so I'm closing this thread. If we need to discuss further on the forum, feel free to post again.