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TCA8418: KP_LCK_TIMER issue

user5898245
Prodigy 20 points

Part Number: TCA8418

Hi, I'm trying to enable UNLOCK1 to UNLOCK2 timer to use the right side part of the flowchart from pag19 of the
datasheet (KP_LCK_TIMER[7:3] == 0). I set the timer in 3 seconds but for some reason it does not start again
when the time is up, instead, it waits indefinitely for the next key.

Previously I configured the registers in the following order:

CFG = 0b10000100 (only K_LCK_IEN enabled) 

UNLOCK1 = 129 (pressed)

UNLOCK2 = 130 (pressed)

KP_LCK_TIMER[7:3] = 0

KP_LCK_TIMER[2:0] = 0b011

KEY_LCK_EC[6] = 1

I checked this reading LCK1 / LCK2 flags. LCK1 stays at 0, and only returns to 1 when a wrong second key is pressed.

Sorry for my english.
Thanks

  • 0
    TI__Genius 16575 points

    Hello,

    Very interesting what you're running into. I just did a quick sanity check on an EVM I have here with your exact register values you provided. It works as expected for me. The timer does reset the state machine after 3 seconds.

    Let's try some debugging.

    1) When you write to the LCK1 and LCK2 registers, please use the key value instead of the pressed prefix. The device will automatically handle this. So write 1 and 2 to the registers instead of 129 and 130. The TCA8418 should automatically remove the 0x80 prefix from your write. I'd suggest re-reading what you write just to make sure the expected values are making it in.

    2) Please try setting the KP_LCK_TIMER[7:3] to 0b00011. This means you would write 0x1B to KP_LCK_TIMER. See if this fixes your time out issue.

  • 0 in reply to Jonathan Valdez
    Prodigy 20 points
    I wrote 0x1B to KP_LCK_TIMER and works fine, LCK1 flag returns to 0 and restart. This is a normal functioning?
  • 0 in reply to user5898245
    TI__Genius 16575 points
    This is not intended behavior. It appears that this is a bug specific to the non-E variant of the device. If the timer mask is set to 0, it never restarts the state machine, causing infinite wait time.
    The TCA8418E does not have this bug, but also is offered in a WCSP only.

    We will need to add this to the datasheet for the non-e variant for others. Thanks for bringing this one to our attention.