Hello all,
As an adviser, I have been asked to look into an irritating problem as follows:
On a keyboard design using TCA8418RTWR driven with NXP LPC1778, a customer has found a problem as follows:
When pressing the C2R0 button several times repeatedly at random number of strokes, another key (always C1R0) will be activated.
This phenomenon repeat itself on many boards (not all). Note, these are adjacent columns, same row!)
We checked and excluded the keyboard itself, the connections and the PCB (including X-ray), and replacement of the device, but the problem remains.
I suspected a leak on the board (could not find any!. Isolation was always > 8 MOhm) or a driver marginal timing issue.
Next we will have to dig into the software driver, but before we do that (it is software written by unknown with poor documentation) I want to ask if anyone has encountered a similar problem or have an idea what the source of the problem can be or any idea on what to check further.
Thanks in advance,
SamTal