Having trouble calibrating LCD7 with no XDM

I’ve customized my distribution; the intentions are to run Qt either to the XServer with no display manager, or directly off the frame buffer.

I did start with the default Angstrom 3.8.13 kernel and root file system. I don’t believe I customized the kernel at all with the exception of modifying the FTDI serial driver, therefore not really related to any display.

My setup is Beaglebone Black with the 7" Touch LCD CAPE.

How I’ve modified the boot up is that I do run XServer, but do not run a display manager, instead I’d run my Qt application as part of my xinitrc. Right now it just happens to run an xterm as I develop my Qt app. This all happens at boot, if I were to disable loading the XServer, then my display would merely show the Angstrom login prompt at the command line.

I happened to attach a USB keyboard and from my XServer it did not work; I’m not thinking that maybe I can just go to command line and maybe that keyboard will work.

The way I talk to it now is via the serial 232 console on J1, or I can ssh to it, but mainly I do use the serial console.

A draft Qt application was created, a few buttons and I can activate those buttons if I manage to get the right touch; appears right now that touch calibration is almost random, probably because it never occurred at all.

So I have xinput_calibrator as well as the script, they were already there. I do see the documentation that by default it should come up when you run your board in the out of the box mode, but as I’m saying, I’m far away from that point. I can of course unplug my microSD card and run the default provided Angstrom and also erase the calibration file to cause that to calibrate again. This thought as I draft here is giving yet another idea.


  • Wondering if I can get to be able to run xinput_calibrator, right now it always tells me that it cannot connect to the XServer; my attempt have been to try and run it from my serial console or via ssh offering it arguments like “–device :0” and no joy. Also have run ssh with -X and -Y options and similarly not been able to get xinput_calibrator to agree that it can run.
  • Given my problem of no keyboard running while my XServer is running that’s sort of a bummer, I will check my system log to see if there’s anything obvious; because potentially with that one xterm running I may be able to run xinput_calibrator from that terminal and it will then see the XServer.
  • My thinking on calibrating under the default Angstrom build is that I can grab the calibration file and copy it to my SD card so that when I boot it, it will consider that data to be the valid calibration. This last one is actually my thoughts towards my next, first step.

If anybody sees some sort of other solution path, I’d be interested to read your inputs. Sorry if these thoughts are somewhat disorganized; I think you can tell that as I write this I’m getting new ideas during composition.

Best Regards,

  • RT

Ok, topic is a few weks old but if you're still stuck on this...

You should read this :

I use tslib for touchscreen under Qt4, and you can calibrate the screen with ts_calibrate and then use the touchscreen for qt apps.

I came across another problem, being the pressure needed on the screen, but that's something todo on my list.

Under qt5 there's evdevtouchscreen wich is also working.