Hi,
       I too am interested in knowing how to do this. I posted a similar query a few days ago but got no reply.

While I wait for some answers, here are my thoughts.

a. The onboard A/D converter for the OMAP35xx chip could be used to interface with the touch screen. 

b. Another alternative is to use the TI TSC2007 I2C touchscreen controller chip. I see that on the Linux-OMAP mailing list, there is some active development by the folks at TI and they are adding support for the TSC2007 touch screen controller into the linux-2.6 kernel. I'mYou'll need to interface the Overo to the TSC2007 using the OMAP35xx I2C port.

c. After that, in order to interface the OMAP35xx low voltage signals to the 3.3V required by the LCD module, perhaps you will need to use a TI AVCA (B) 164245 Translation Device for LCD Module interfaces. 

d. The LCD display panel that I am thinking of interfacing with is a Sharp LQ043T1DG01 4.3" 24-bit color LED backlight display with an analog resistive touch screen panel. 

Let me know what you think! 

I'm not so certain about the following assumptions, and haven't validated them, just penning some thoughts down from what I've glanced through quickly, I need to do a bit more reading:
- that the A/D converter can be exposed on the Overo motherboard, to interface with the LCD touch screen
- that the logic levels for driving the LCD display are at 1.8V, requiring the use of the translation device

Best regards,

Elvis Dowson


On Dec 10, 2008, at 10:52 PM, Cliff Brake wrote:

Hello,

I'm mapping out the I/O on the gumstix overo and have a couple questions:

1) The PMIC chip markings are PTPS6590A.  I can't find documentation
for this exact PN on TI site.  There is TPS65950 which is likely very
similar, but wondering if anyone knows if these are the same ICs, or
is the 6590 something different.

2) what support is there on the overo hardware for resistive touch
screens?  I see a GPIO127_TS_IRQ signal on J1, but I don't see any
other evidence of touch screen functionality in the signal names, or
in the TPS65950 datasheet (if that is what overo is using).  Is the
plan to use an external touchscreen controller, or am I missing
something?

Thanks,
Cliff

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Cliff Brake
http://bec-systems.com