I am using ADS 7843. Touch screen is working almost 100% time, with bench setup. But once we install setup in noisy environment we have random button press near x = 0 location. Software check PENIRQ pin 16 times before it decide that pin is really pulled low.
PENIRQ pin is tied to 5 V (Vdd) with 100 K Oh pull up resistor.
If nothing is pressed on touch panel, I am getting ~3.5 V on PENIRQ pin (with 100K Pull up). (Measured with scope). If I decrease pull up resistor (to 10 K) I am getting ~4. 8 V on PENIRQ pin.
I am able to get it working in noisy environment with 10 K Pull up on PENIRQ pin.
My question is,
If I reduce pull up resistor, how it will affect Vol ? Do I have to add any additional precaution in software or hardware after this change? (Currently I am doing average of three out of nine samples)
Regards,
Jigar