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TCA8418: TCA8418

prabhulinga bhavikatti
Prodigy 50 points
Part Number: TCA8418

Hi,

I am using TCA8418 keypad Ic's in my application .i am using STM8AF controller in my application.Some times when I  do multiple operations In scenarios I am missing release value instead of release i am getting which ever button is pressed that value i am getting

Ex:

130 is key1 it is pressed.

after if iam pressing 142,153,139, In releasing i should get 14,23,11 .In some cases i am getting 14,23,130, so missing some release command.Please suggest

Regards

Prabhu.G.Bhavikatti 

  • 0
    TI__Guru 62920 points
    Hi Prabhu,

    Are there certain combinations of key presses that can always reproduce this issue? If so, maybe it is related to ghosting (see the datasheet for a description of this). Otherwise, if the issue seems to show up randomly regardless of the key sequence it may be a more "analog" kind of issue. If that is the case, are you able to monitor the voltages at the different key inputs/outputs to verify connectivity and see if the signals look correct?

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 50 points

    Hi,Robertson

    We have taken care of ghosting errors.The above issue appears randomly,and some times I'c completely stops operation(It doesn't acknowledge).when we power cycle the system it works properly.Is there any things to take care in software? please suggest me.

    Regards,

    Prabhu

  • 0 in reply to prabhulinga bhavikatti
    TI__Guru 72751 points

    Hey Prabhu,

    "Ex:

    130 is key1 it is pressed.

    after if iam pressing 142,153,139, In releasing i should get 14,23,11 .In some cases i am getting 14,23,130, so missing some release command."

    A. Question about your example, when you press 130 then 142, 153 and 139 are you releasing 130 anytime before or are you actually holding it the entire time?

    B. You state you should be seeing 14, 23, and 11. Do you mean you should be seeing 14, 25, and 11?

    "We have taken care of ghosting errors."

    Are you taking care of ghosting through software or through hardware?

    Can you provide a schematic we can review? (just our TCA8418 device)

    When you initially turn on the device, are you meeting power supply requirements of the device? (section 10 of datasheet)

    After power cycling, does the issue every come up again? (if not this sounds like it may be related to the device's start up.)

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 50 points

    HI Bobby,

    A. Yes I am holding  it for entire time.

    B. Yes,I mean 25.

    C. We are taking care of ghosting error by hardware side avoiding the particular row ,and columns.

    D.Yes we are meeting power supply requirements.

  • 0 in reply to prabhulinga bhavikatti
    TI__Guru 72751 points
    Hey Prabhu,

    Thanks for the clarification.

    Do you think you can post a schematic? (with just our device)
    -I'd like to review it and make sure everything looks okay.

    Is this an issue that is easily repeatable?

    Could you also send o-scope shots of when this error occurs?
    -I'm wondering if the signal may be corrupted on I2C lines somehow.

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Prodigy 50 points
    Hi, bobby
    I got the solution .While reading I2C I didn't give the Delay when I added Delay it is working fine.Thanks for your help

    Regards
    Prabhu.G.B
  • 0 in reply to prabhulinga bhavikatti
    TI__Guru 72751 points

    Hey Prabhu,

    Great to hear! Glad you got back to us about this too, as I'm sure others may run into this issue in the future and knowing how to fix this will help others later on. I've marked your reply as verified answer for others to refer to.

    Thanks,
    -Bobby