TCA8418: False Key Event

Branimir Maximov

Part Number: TCA8418

Tool/software:

Hello!

I have encountered a bug where, in between a correct key press and key release event, I would get a false key press and key release. This does not always happen, and when it does, it is very brief. Not only this, but I only see this duplicate key only when pressing a particular key.

As an example, with keycode:

129 and 1 should be the only keycode, but 130 and 2 would be produced falsely.

I set the KP_GPIO to 1s for Matrix, GPI_EM to 0s, GPIO_INT_EN to 0s, DEBOUNCE to 0s to enable, and CFG to 0x19.

If anyone has encountered this issue before, or knows what the problem could be, I would appreciate any input. Thanks!

tca8418.pdf

10 months ago

0 Tyler Townsend 10 months ago

TI__Guru 52698 points

Hi Branimir,

Have you double checked your key event case with the ghosting considerations in section 9.1.1 of the datasheet? Can we rule out ghosting?

Regards,

Tyler

0 Branimir Maximov 10 months ago in reply to Tyler Townsend

Prodigy 20 points

Hi Tyler,

Thanks for your response. I believe we can rule out ghosting because only one key is being pressed in my case instead of multiple.

Best,

Branimir

0 Tyler Townsend 10 months ago in reply to Branimir Maximov

TI__Guru 52698 points

Hi Branimir,

Do you have a schematic available for review?

Can you also double check for any soldering errors in the switch array or soldering errors on the chip itself?

Regards,

Tyler

0 Branimir Maximov 10 months ago in reply to Tyler Townsend

Prodigy 20 points

Hi Tyler,

Yes, I do! I am attaching it here. I don't see any soldering errors, but I might have an inkling that there could be improvements via adding pullup resistors on the Row/Column pins. Are the internal pullup resistors not enough?

The upper part of the schematic not shown is left open via no jumper as a fallback using GPIO for key detection.

Thanks! Best,

Branimir

0 Jack Guan 10 months ago in reply to Branimir Maximov

TI__Mastermind 44451 points

Hi Branimir.

We are still looking into this and will update here.

Thanks,

Jack

0 Branimir Maximov 10 months ago in reply to Jack Guan

Prodigy 20 points

Hi Jack,

Thank you!

Best,

Branimir

0 Jack Guan 10 months ago in reply to Branimir Maximov

TI__Mastermind 44451 points

Hi Branimir,

The team is out on US holidays today and responses will be delayed. Thank you for your patience.

Regards,

Jack

0 Branimir Maximov 10 months ago in reply to Jack Guan

Prodigy 20 points

Hi Jack,

Thank you for the update. I look forward to hearing back when possible.

Best,

Branimir

+1 Joshua Salinas 10 months ago in reply to Branimir Maximov

TI__Mastermind 28020 points

Hello Branimir,

Tyler is currently out of office so let me try and help here. Looking over the datasheet, it does note that every row or column pin that's unused should be pull-up (10kΩ) to VCC. Is it possible to try this on ROW 4-7 & COL 5-9.

Regards,

Josh

0 Branimir Maximov 10 months ago in reply to Joshua Salinas

Prodigy 20 points

Hi Josh,

Thank you for the advice! We will implement this on our PCB, and I will write back when we can test it.

Best,

Branimir

0 Joshua Salinas 10 months ago in reply to Branimir Maximov

TI__Mastermind 28020 points

Hello Branimir,

Sounds good! Let us know if there are more questions.

Regards,

Josh

0 Tyler Townsend 10 months ago in reply to Branimir Maximov

TI__Guru 52698 points

Hi Branimir,

FYI, just got back to office today. Just as Josh stated, let us know if you have any more questions.

Looking forward to the updates to the PCB. Let us know if this resolves the issue.

Regards,

Tyler

0 Branimir Maximov 10 months ago in reply to Tyler Townsend

Prodigy 20 points

Hi Tyler and Joshua,

Apologies for the delay. After the CNY, our factory implemented the pullup resistors, and it has resolved the issue. Thanks!

Best,

Branimir

0 Tyler Townsend 10 months ago in reply to Branimir Maximov

TI__Guru 52698 points

Hi Branimir,

Sweet. Glad to hear Josh's recommendation worked!

Regards,

Tyler

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TCA8418: False Key Event