Touchscreen driver issue

[bibinpaul]

Hi,

I am using GLCD 128x64 Touch Screen from Mikroelectronica on a project. The touchscreen driver circuit is copy of the one on PIC18 development board(Easy PIC V7). I am using PIC18f67k22 to control the display and touchscreen.

The problem I am facing is, I get a full 0 Volts to 5V on one axis of the touchscreen. On the other axix, the variation is very small 0.7V to 1.7V. I have tested this with the sample code given by Mickro electronica. I have worked on touchscreen and familiar with driving the touchscreen and reading the ADC values.

Issue appears to be on the driver circuit comprising of transistors and resistors. I have seen similar designs with different resistor values.

Any help is really appreciated.

Thanks,
Paul

 

[Ian Rogers]

Same!!! I ditched the driver board and used the TFT touch driver instead..

The circuit is simple... Each drive has a 300k pullup with a 47nf decoupling cap..

I use a pic32 so

Drive X and read Y are on one ADC pin
Drive Y and read X are on another...

The circuit is in the help file under Touch Panel TFT... This is a FAR better solution...

 

[bibinpaul]

Thanks for the reply, Ian. Ur design is simply great.

I was also planning to see if it works from GPIO/ADC pins.
unfortunately, I cannot change the design(or add a touchscreen controller). Hardware is already designed by someone else, copying the Mikroe design.

Looks like its some odd resistor combination.

cheers,
paul