Re: Touch screen PENIRQ problems with AD7843

On Apr 29, 3:55 pm, Neil Bradley <nb_no_s...@xxxxxxxxxxxx> wrote:
Dingo wrote:
Does anyone have any clues as to why this might be occurring? It's
obviously something simple, but we can't figure out what! In the mean
time, we have some old 3rd party devices that have the AD7843 in them
and we're going to examine its behavior, but in the mean time if anyone
has any hints or suggestions, it would be most appreciated.
Since you can't seem to determine if it's a software or hardware
issue,
you should try a simple test:
1. Remove any code that would cause the AD7843 chip-select to be
asserted.

Thanks for the reply, Dingo.

The AD7843 needs to be programmed up to drive the PENIRQ, and I
mentioned before that I had tried both possible settings for it. Not
allowing !CS would surely make PENIRQ not work. Plus, the code doesn't
poll the 7843 unless PENIRQ gets asserted anyway.

From the data***: "On power-up, PD0 defaults to 0,
while PD1 defaults to 1."

And: "This configuration results in keeping the AD7843
permanently powered up with PENIRQ enabled."

So PENIRQ is automatically enabled at power-up.

I think it would be quite valuable to test the behavior
of PENIRQ before software configures the AD7843.

.

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