Problem connecting the ET070080DH6 7" EDT resistive touch screen with iMX7d

When attempting to attach the screen mentioned in the subject, I’m running into problems. The backlight doesn’t activate, and /dev/fb0 just writes to the VGA output.

I’m not seeing anything in the kernel event logs indicating that the device is even detected, though I could be looking in the wrong place.

I get no additional entries in /dev nor /dev/input (so no touch events nor video output). Is there some jumper fiddling I need to do? An additional kernel module I need to build? A device tree entry that isn’t in the default evaluation board’s device tree? All the hardware is Toradex reference implementation stuff purchased directly from the Toradex web site, so you know everything about the environment.

The kernel, u-boot, and device tree are all from the Colibri iMX7d Toradex image.

When attempting to attach the screen mentioned in the subject, I’m running into problems. The backlight doesn’t activate

Unfortunately the back light polarity is not standardised. Have a look at the following article about the same.

and /dev/fb0 just writes to the VGA output.

Yes, as most our carrier boards implement their ramdac off the same parallel RGB.

I’m not seeing anything in the kernel event logs indicating that the device is even detected, though I could be looking in the wrong place.

There is really no detecting such a resistive “dumb” touch display. Either the resolution and timing you configured is appropriate or you won’t get anything output. And either the touch is connected properly and the resistive values sensed make sense or you won’t get any touch events.

I get no additional entries in /dev nor /dev/input (so no touch events nor video output). Is there some jumper fiddling I need to do? An additional kernel module I need to build? A device tree entry that isn’t in the default evaluation board’s device tree?

No, usually not.

All the hardware is Toradex reference implementation stuff purchased directly from the Toradex web site, so you know everything about the environment.

The kernel, u-boot, and device tree are all from the Colibri iMX7d Toradex image.

Nothing in a resistive touch screen is “detectable”. All our BSPs should have loaded the resistive touch screen input device by default.