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MSP430F5359: SDA become continuously low

Part Number: MSP430F5359

Hi team,

My customers having difficulties with MSP430F5359IPZ and I’d like to ask your advice. They are using I2C for communication but it is not working as expected.

The issue is, somehow SDA signal become continuously Low.

The trigger of this event is unknown. When this happens, SCL signal become continuously High.

The structure is, [Control board] – [level shifter for I2C] – [Device-A/ Device-B]. Device-A and Device-B are on the same path line. The communication destination determined by address setting. Both line are pulled up with 2.4kohm and communication speed is set as 100kHz. The pins used are 73 and 74.

Would somebody know the possible cause of this phenomena?

Best regards,

Kurumi Hasegawa

  • Hi Kurumi,

    Is the MSP430 the control board here or Devices A/B? If it's the control board, what are Devices A/B?

    Does this issue occur when the level shifter is removed? Have you checked the erratasheet for any I2C-related issues?

    I'd encourage you to divide and conquer the system to identify what's pulling SDA low. I'd also recommend looking through the Solutions to Common eUSCI and USCI Serial Communication Issues on MSP430 MCUs app note.

    Regards,

    James

  • Hi James,

    Thank you for the reply and providing helpful material.

    Is the MSP430 the control board here or Devices A/B?

    ->MSP430 is the control board.

    If it's the control board, what are Devices A/B?

    -> One is I2C interface DAC (MCP4725) and the other is smart battery.

    Does this issue occur when the level shifter is removed?

    -> It occurs when the level shifter is removed.

    Have you checked the errata sheet for any I2C-related issues?

    -> I checked errata sheet and found some related to I2C issues. But not so sure if it is the cause. The revision is B.

    So, the hypothesis that the customer came up with is that both smart battery and MSP430 became master, which leads to the signal collision. There is a possibility that the software is created without any protection against signal collision.

    Could this be the cause of the issue here? What would be expected to happen when signal collision occurs, if the software setting does not expect signal collision?

    Regards,

    Kurumi

  • Kurumi Hasegawa said:
    So, the hypothesis that the customer came up with is that both smart battery and MSP430 became master, which leads to the signal collision. There is a possibility that the software is created without any protection against signal collision.

    Does the issue happen when the smart battery is removed? If one of the devices is pulling down on the I2C bus, then it doesn't really matter what the other devices do since it's open-drain control. It's not like the MSP430 can pull the bus back up when another device is pulling it down. Perhaps I'm misunderstanding your question.

    Regards,

    James

  • Thank you for the reply. Maybe I just miss-conveyed the original question...

    I've got a file that I want to share with you via e-mail. Could you please check the mail I sent?

    Regards,

    Kurumi Hasegawa

  • This discussion has moved offline.

    Regards,

    James