hello mentor_guy,

How far along are you with the touch panel?
If debugging, refer to the schematics and hook a scope up to the SPI lines to monitor the transfers. What touch x/y values do you observe at each of the four corners? Are there any other inconsistencies?

Sharp has sample code available through both http://able.sharpsma.com and http://quickplace.sharpsma.com. For the quickplace site, click the "My Places" link in the upper left corner, then "sma_sis_lh79520".

The Linux BSP source is available there, along with other LH79520-10 example code.

Regards,
Andrew Wawra
Tech Support
Logic Product Development

I have downloaded and run some test applications/code from Sharp. The values are incorrect. I get xy values such as:

Top left corner (4000, 0)
Top right corner (0, 0)
botton left corner (4000, 4000)
bottom right corner (0, 4000).

Keep in mind. These are just estimates.

I am trying to get values based on a 640 x 480 screen.

Hey, mentor_guy,

Andrew pointed you to the right place for Sharp sample code. BTW, http://able.sharpsma.com is the easier of the two to navigate and find what you need relative to software development. If you need data sheet and user guide type info, you can find it at http://www.sharpsma.com and click the MCU & SoC link.

Unless someone else is experiencing exactly the same issues, I suspect we've covered this outside this forum. However, for the benefit of others, and just in case I'm wrong, I'll risk repeating myself.

Since the touch screen controller on the SDK-LH79520 is external to the MCU, I'm guessing that you were using a variant of the code from the SDK BSP in the touch screen example program, namely /sharpmcu/software/csps/lh79520/bsps/sdk79520/examples/touchscreen.
The read out from this code, specifically the touchscreen_get_raw_position function, is raw data. The measurements need to be scaled to the panel size and adjusted for the x/y origin in the application.

An application (or OS) will need to calibrate the touchscreen interface and adjust future touchscreen measurement as needed. If you have a PalmPilot or equivalent, it has this as part of its initial setup. Also, the Linux port Andrew mentioned also requires touchscreen calibration.

Regards,
Chris Noonan
MCU FTM (a.k.a. FAE)
Sharp Microelectronics of the Americas