• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 108 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

P82B96: Use as GPIO Extender

Matt Nixon
Prodigy 30 points
Part Number: P82B96

Tool/software:

Hi, 

I'm looking to create an I2C link which will operate over approximately 5m of cable, the P82B96 looks like a good choice for this. The extended I2C lines will not constantly operate as I2C, but for some of the time one line will carry a GPIO logic level. Is the P82B96 suitable for this application?

Best regards, 

Matt

  • 0
    Guru 272660 points

    The P82B96 works only with open-drain signals. When the P82B96 drives low and some other device drive a high voltage, then both devices could be damaged.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hi Clemens, thanks for the quick response.

    My intention is to have microcontrollers at the master and slave sides operating as I2C, then under certain conditions the I2C lines will switch to GPIO functionality with the slave side controlling the state of the lines. The microcontroller GPIOs will be configured to operate in open drain mode in all situations.

  • 0 in reply to Matt Nixon
    TI__Mastermind 29303 points

    Hi Matt,

    The VIT thresholds are consistent across the VCC range of the device. 

    P82B96 is an open-drain I2C buffer. Following these VIT thresholds, the buffer will either release HIGH, or drive strong LOW. 

    Is there any point where the MCU would toggle LOW while the target pushes HIGH? What I am asking is if there is any instance in time where the MCU and the target communicate at the same time? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 30 points

    Hi Tyler, 

    Not on the same line. In the case of switching from I2C mode to GPIO mode, the master will send a specific code the the slave. At this point the slave will control the state of one of the I2C lines as a GPIO in order to signal an event to the master side. When the master side needs to signal the slave to re-enter I2C mode it can pulse the other I2C line, so there will never be any time that one line could be driven from both sides at the same time.

  • +1 in reply to Matt Nixon
    TI__Mastermind 29303 points

    Hi Matt,

    Given this specific case, I don't see why P82B96 wouldn't work with GPIO signals since we won't run into contention issues. VIT thresholds would need to be followed at a minimum. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 30 points

    Hi Tyler, 

    Thanks very much for your help!

  • 0 in reply to Matt Nixon
    TI__Mastermind 29303 points

    Hi Matt,

    Thank you for posting your question. If you have any additional questions, feel free to submit another e2e question. 

    Regards,

    Tyler