Question

I have Qt Embedded 4.7.4 working on an ARM system, in order to display graphics application on a touchscreen. Everything works pretty good with tslib and framebuffer, no problem concerning the display and the touchscreen.

But I would also like to be able to use an USB Keyboard to find my way through the application. I already have a keyboard linked to my ARM system, that works great. Its driver is a basic tty driver, I can read the information I typed by reading /dev/tty0

So I thought Qt would be able to do the same, by exporting QWS_KEYBOARD=/dev/tty0 ; I tryed many things but nothing seems to work. Qt doesn’t detect any events ; I tried another thing, ’cause I saw that my keyboard events were also send to /dev/event1. So I export QWS_KEYBOARD=TTY:/dev/event1 and this time Qt detected some inputs. But they are not good, in fact there is all the time inputs even if I don’t press any key.

Do you have any idea ? Maybe the reason is that /dev/tty0 has a buffer, and this unable Qt to work?

Answer 1

I faced a similar problem today, albeit with an Intel Atom processor. My linux distribution is ptxdist. I noticed that plugging in a USB keyboard creates two event* entries in /dev/input and only one of them yielded useful input. Using udevadm, I figured out that they differ slightly in their attribute fields, so that I could find the right one. My udev rule boils down to

KERNEL=="event*", SUBSYSTEM=="input", ATTRS{bInterfaceNumber}=="00", ATTRS{bInterfaceClass}=="03", SYMLINK+="keyboard"

which creates a symlink /dev/keyboard to the correct device. To use this device, I used

export QWS_KEYBOARD=LinuxInput:/dev/keyboard

which works for me.

Hope this helps…