PanelDue (7i) button accidental button presses

jml

When pressing buttons on the screen, for instance, when jogging the printhead after pressing the "Move" button on paneldue, I notice that occasionally (rarely, but enough to notice) that the panel thinks I have clicked elsewhere on the screen instead of where I intended to click. Does this happen to anyone else?

I do notice that if I press in two places at once, it will think that I have pressed at halfway between these points.

I am thinking that perhaps another part of my hand is close enough to the screen for it to think it is a press - does the screen sense presses with capacitive in addition to actual pressure on the screen?

And is it possible to change the screen firmware to ignore presses in which there are two distant points being pressed at the same time? I'd rather have it ignored rather than pressing a button in between the points which it seems to do.

dc42

The touch screen is resistive, so it senses pressure not proximity. It's more accurate if you use the tip of your fingernail to touch it, not the pad of your finger. The electronics can't tell if it is being touched in more than one place.

Jacotheron

I would check the display for possible damage.

The PanelDue uses a resistive touch panel, which is cheap, but simply can't handle more than a single press at a time. This is compared to the capacitive touch panel used on smart phones and other electronics, that can distinguish between different areas being touched at the same time.

In very short, the touch controller chip measures the resistance from top to bottom and then from left to right. When that changes, it determines a position by how much it changed (as a fraction, that is used to calculate a quite accurate X and Y position). Touching 2 places at the same time, means the measured resistance is between the 2 places, as you have experienced. It simply can't ignore the 2nd tap. The main controller chip, simply receives the relative position of a touch, calculate where that should be, and perform the required action.

The "thinks I have clicked elsewhere on the screen" - is that towards the edge of the display in any specific direction?

In my own recent question, my touch position would be registered at the right edge of the display (towards the buttons' side). It turned out my touch panel had a hairline fracture on a corner, that rendered the touch panel useless.
If your display touch issue is intermittent, it may be easily fixable but also harder to detect.

On mine (an 5i), I have now ordered a replacement touch panel, the one that will fit your display is https://www.buydisplay.com/default/7-inch-4-wire-resistive-touch-screen-panel (you won't need the connector and driver board that can be added).

I have figured out that to replace the touch panel, the following instructions should work (since the touch panel is identical to what is already on your display):

Wait until the replacement panel arrived, before removing the original panel, and do so in a slightly humid area with the least amount of dust possible - slightly humid (though not too humid - electronics does not like too high humidity) may reduce dust. We do not want dust between the touch panel and the display.
desolder the original touch panel's 4 wires, and peel the touch panel off, starting in a corner. The Touch panel is the whole part above the metal casing from the screen (it includes a glass panel).
the new touch panel comes with adhesive that will stick it to the display, carefully peel the tape from the adhesive side of the new touch panel; position the touch panel and let it stick in the right location (starting in a corner, like you would install a screen protector).
solder the new 4 wires to their location, ensuring a good solder joint.
power the display, possible using USB to make it easy, and run the calibration - this should ensure that the correct positions are detected as the limits.
the display should now be functioning.

jml

I will test again when I have access to the screen. I could have sworn that if I held one finger constantly pressing down, and then if I press somewhere else on the screen with a different finger, the press is registered as halfway between. Will test thoroughly and update this thread.

Mine is like this:
https://www.thingiverse.com/thing:2415439

But perhaps I screwed the screws to tight and the panel is pressing too hard against the paneldue.

dc42

@jml said in PanelDue (7i) button accidental button presses:

I could have sworn that if I held one finger constantly pressing down, and then if I press somewhere else on the screen with a different finger, the press is registered as halfway between.

That is exactly what I would expect to happen.

jml

@dc42 Ok, so if I'm occasionally getting presses registered in places where I am not actually clicking then I guess that means either my mount is pressing against a touch-sensitive part of the screen a little bit, or the touch-sensitive part of the screen is faulty.

It doesn't happen often, and it hasn't happened enough for me to notice any particular pattern (like towards one particular edge).

Alexander Mundy

My original 7" does this occasionally.

T3P3Tony

@jml yes. Are you able to try the screen out of the mount to confirm? How often does it happen?

dc42

@jml said in PanelDue (7i) button accidental button presses:

@dc42 Ok, so if I'm occasionally getting presses registered in places where I am not actually clicking then I guess that means either my mount is pressing against a touch-sensitive part of the screen a little bit, or the touch-sensitive part of the screen is faulty.

Yes. In a high humidity environment, condensation on the connections to the touch membrane might also cause that problem.