Hello,
We are using the 7" Capacitive Touch Display (Capacitive Touch Display - 7 inch), and it would suit our needs just fine. There is one issue: The contrast is poor when viewing from the front (at right angle) and getting worse when viewing from slightly above. The contrast is much better when viewing from below. It would be perfect if we could get this contrast when viewing from the front!
Is there an adjustment, or is this how it is with this display? I understand that Toradex does not focus on selling displays, but other than this issue we don’t need anything else at the moment.
[upload|sHUvLyM16Oz7i7SkDOA0DQOIlNQ=]
Very good contrast when viewing from below: rounded buttons, the side bar is clearly visible.
[upload|LdzP9hWOw3isJEZSVt7QHbActUY=]
Poor contrast when viewing from the front (center): Buttons appear almost flat, the sidebar is not visible as well as when viewing from below
[upload|zfEvC7ThQF+4xWaUpN/VE+l9v4I=]
Contrast gets event worse when viewing from slightly above: It gets even hard to distinguish whether the sidebar is at top or at bottom
Hello Janani,
Sorry, I’ve forgot to post vidargs settings. As far as I know these are the recommended settings. I’m using:
vidargs ‘mxc_hdmi.only_cea=1 video=mxcfb0:dev=lcd,FusionF07A,if=RGB24 video=mxcfb1:off vid-eo=mxcfb2:off video=mxcfb3:off fbmem=32M’
Thank you for your information. In that case, you are sure about the vidargs setting, you could achieve the contrast variation by changing the backlight and drive strength of the pixels. Please refer to this article here: Device Tree Customization | Toradex Developer Center
You could change to a lower ohm value and check if that brings in the desired changes.
Hello Janani,
It may take a little while until I have enough time to try this out, but I will do it as soon as I can. Thank you for your help, I will let you know once I have a result.
Best, kbraendle
It’s been quite a while since I have posted this question. Just as a little recap, the issue is that the contrast (7" Capacitive Touch Display) is very good when looking at the display from below, and becomes really bad when looking at it from above, to the point where it is impossible to see whether a scrollbar is at the top or at the bottom (this is an issue for tall people when standing in front of the display that is installed on a machine).
I have made a few attempts, with the device tree customization, but I did not really find what I have to set to achieve a drive strength difference (my problem was not the device tree customization, but what values to set). In the end, I left it unchanged and was busy with other things. But now it has become an issue again, as we have some complaints and we really want to fix it.
Can you give me some further help on this topic?
We are using Apalis iMX6 with Ixora Carrier Board, and since the original post we have changed to Linux BSP 5.7, using device tree overlay (overlays.txt) “fdt_overlays=apalis-imx6_lcd-lt161010_overlay.dtbo apalis-imx6_atmel-mxt_overlay.dtbo”
If this becomes too complicated or goes out of scope, we are willing to purchase some hours of technical support from Toradex in order to get this corrected.
According to the display datasheet, the viewing angle is limited to 50-60 degrees relative to the direction perpendicular to the screen surface. This limitation is inherent to the a-Si TFT technology used in this screen and is also prone to the gray scale inversion phenomenon. Unfortunately, adjusting buffer strength or brightness won’t significantly improve this limitation, and in some cases, it might even worsen the display quality. Please check this article for more details.
If your application requires a wider viewing angle, you may want to consider a display based on IPS TFT technology, such as the Capacitive Touch Display 10.1" LVDS, or opt for a screen using OLED/AMOLED technologies.
Hi Alex, thank you for your quick response! I’d still expect a perpendicular viewing angle to yield the best result? A viewing angle from lower than perpendicular (even to a very high angle!) yields a better and sharper image than perpendicular. Even at very high viewing angle, this is really good. It gets worse quickly if the viewing angle is above perpendicular, already at 10°! If it was anywhere near 45°, it’d be totally acceptable.
I have now rotated the display by 180° (“xrandr -y -x”). This could have been an easy intermediate solution, as users users look at it rather from above than below. But the Qt applications shows a caret in text input widgets, which is ugly and not rendered correctly, and I can’t get rid of it…
Does Toradex know of any 7" touch displays that are compatible and can be connected “easily” to the Apalis iMX6 with Ixora Carrier board? As mentioned already, we could purchase some hours of support from Toradex to get a different display working (I’m in doubt whether I can configure it correctly in adequate time by myself…).
The option to use a HDMI display with USB touch is not ideal, since we have a mechanical setup where the display is in the front, our hardware with the carrier board in the back, and the carrier board plugs are accessible from the outside, so we’d rather not use the HDMI and USB from the outside
