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LM3S6965: I2C SDA pin becomes low at some time

Part Number: LM3S6965

We are using LM3s6965 controller in our current design  

we used RTC 8583 with onboard I2C interface

sometime we observed that its SDA pin remains low and SCL pin remains hi and we get RTC fail error.

Please guide us to resolve the RTC fail issue as problem is occurred on clients site.

Regards,

Anushka

  • Hi Anushka,

      I'm not familiar with the LM3S6965. I can only help from a general I2C troubleshooting point of view. It is hard to say what happens especially your said the problem only happened sometime. Can you answer the below questions?

      - Is it possible the RTC tries to slow down the communication by stretching SCL? This can lock the MCU. 

      - Can you repeat the same problem on all the boards you have or only one board? 

      - Do you have multiple I2C masters on the bus?

      - What is the pullup resistor you have on the bus and is it adequate value? 

      - Do you have the scope cap of the bus when the problem occurs? 

  • 1) - Is it possible the RTC tries to slow down the communication by stretching SCL? This can lock the MCU. 

    It is observed that when RTC fail occurred, SDA line becomes continuous low and SCL line becomes continuous high

    2) Can you repeat the same problem on all the boards you have or only one board?

    We have 5 number of instrument, it shows RTC failure and after Power off/On it is recovered some times 

    we have also replaced the RTC IC but the problem remains same

    3)Do you have multiple I2C masters on the bus?

    NO

    4)What is the pullup resistor you have on the bus and is it adequate value? 

    We use 10K pullup resistor with 3.3V

    5)Do you have the scope cap of the bus when the problem occurs? 

    What do you mean? I donot understand the question

    Regards,

    Anushka

  • Anushka,

      The MCU communicates with your RTC via the I2C. My question in Q5 is if you have oscilloscope or logic analyzer waveform capture of the I2C bus when your problem occurs.  

  • Hi Anushka,

      I have not heard back from. If you can provide a scope cap, it will help troubleshoot the problem. Just to give you a heads up, I will be out of office next week. I will close the thread for now. If you have some update you can reply back to this post to reopen the thread. However, I will suggest you open a new thread and reference this thread to continue this discussion so our support team can support you.  

  • Problem instruments are on the client site, so that we are not able to scope cap the details. We are trying to generate the same problem at our place 

    We will send you the details as early as possible

    Regards,

    Anushka

     

  • Hi,

      Do you have some update?