Issue with Toradex 7" capacitive display on iMX6/WEC7

  • We are changing the display on our iMX6/WEC7 solution from a Newhaven 7" display to the Toradex 7" model.
  • Because we use the Iris carrier the solution includes the Capacitive Touch Adapter. The wiring was straightforward and we got all the required info from this page .
  • In particular, the registry settings were obtained from this sub-page, under section 2.4: Settings for all Colibri and Apalis Modules. We just used the default values from that section, except for CXScreen and CyScreen, which are 800x480.

The display comes up OK but there seems to be some setting that not quite right, because the pixels seems somewhat mashed together, as if there is some re-sampling going on. It’s hard to explain so I’ve included photos that illustrate the problem. Notice that on the Toradex display that “My Device” is pretty much illegible. Also, in the Explorer the Newhaven text looks nice and crisp whereas on the Toradex display it’s blocky and somewhat green in the menu font.

I’m convinced that this is some incorrect setting but I’m unable to find any other info besides what is in the links I refer to above. Are those registry settings applicable to this display?

alt text

Dear @guzoo

Adding the picture was a very good idea. This helps a lot to understand the nature of wrong display settings. Sometimes even a short movie is helpful, but in this case not required.

The effect you see is usually caused by a wrong pixel clock polarity - the display samples the data of each pixel exactly in the moment when the data changes.
Simply try to change the value, this should fix your issue.

"pcp" = dword:0     ; I assume you used 1 so far

The default values you found in the article Display Driver Registry Settings are for a display with VGA resolution. You should adjust the timings according to the display datasheet.
Displays are often quite forgiving when using wrong timings, but for example if you stay with the default 25MHz pixel clock and increase the resulution to 800x480, your refresh rate will drop to roughly 50Hz.

Regards, Andy

The fix to the pixel clock polarity did the trick. The Toradex display looks great now. Thanks (again) for the help.