• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 28 subscribers
  • Views 1702 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Linux/DLPC900: Problem with I2C communication

Nima Sarrafi
Prodigy 70 points
Part Number: DLPC900

Tool/software: Linux

I have an issue with I2C communication. My I2C communication is not stable. Sometimes I need to make more than 10-15 calls to send a command. I use TS7970 computer-on-module by technologic systems. The os is Ubuntu. I think the problem is the power because even the output of I2Cdetect is not stable, there are occasions that it doesn't detect my I2C device, namely DLPC900. 

I use 500-ohm resister between VCC 3.3V and my SDA signal as well as 500-ohm between VCC 3.3V and SCL signal. I added two caps on the VCC side of the resistors to get rid of potential noises. They are 470 pF ceramic capacitors.

I would like to know if you have any recommendation regarding this issue.

Thank you.

  • 0
    TI__Guru 54320 points
    Nima,

    I need to consult with our DLPC900 designer to see if he has seen this issue before.

    Fizix
  • 0 in reply to Fizix
    Prodigy 70 points

    Hello Fizix,

    Thank you. I look forward to hearing from you soon.

  • 0 in reply to Nima Sarrafi
    TI__Guru 54320 points

    Hello again Nima,

    Here is what the DLPC900 folks suggested.  They think that you should look hardware to begin with.

    If you using the DLPLCR6500EVM board, there are already pull up resistors on the I2C and decoupling caps on the 3.3V supply.  I suggest removing the additional resistors and caps.  Then, if it still does not operate correct.y,  use a scope to verify the I2C data and clock are truly being sent over the SCL and SCLK lines for every issues transaction.

    If it still does not communicate, try cutting the clock in 1/2 (I assume you are running at 400 kHz) to 200 kHz. And if that doesn't work, down 1/2 again to 100 kHz.

    Let us know how it responds.

    Fizix

  • 0 in reply to Fizix
    Prodigy 70 points

    Hi Fizix,

    Thank you for you and your team prompt reply.

    I will try out the recommendations and keep you posted.