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Argh!

Before anyone looks at this, it seems I do still have myself backwards.

I'm sure once I put my pants on front-wise I'll be out of the Looking Glass on this one.

 

Argh!

Before anyone looks at this, it seems I do still have myself backwards.

I'm sure once I put my pants on front-wise I'll be out of the Looking Glass on this one.

spam removed

No, I set it on one axis I was testing. Should I set it on all axes?

Thanks Rob. I'll get the 7C81 when it comes back in stock.

I thought that I saw somewhere that the 7C81 is now supported in the PNC config Wizard. I could easily be wrong though.

Thanks.

I was asked to post in this thread about a problem I encountered with installing the official LinuxCNC image for the Raspberry Pi 4b. 

The issue I had was once the image was burned to the SD and booted the monitor that I have for the RPi was skewed on the login screen. It looked like the picture below. You could make out what it was showing and could log in and it would take you to the desktop but it was also skewed. You could make out what was there and navigate to the display settings, change the resolution, and get it working, but the changes were not persistent. Everytime the RPi booted it would revert back to the skewed resolution.

It was suggested that the HDMI cable could be at fault, and this is a good suggestion. I did try a couple different HDMI cables with the same results. 

I tried a lot of things from internet searches about this problem, but nothing seemed to work, but I finally found a clue from one post in the internet that was hard to find. I wound up changing several things in the config.txt file in the top level directory of the SD card. I used a Windows laptop to make the changes. Once I had it working, I reversed the changes one by one to see which change was the one that actually fixed it. Here is what I found:

In config.txt you will find this section in there with notes about what I changed to fix it:
[pi4]
dtoverlay=vc4-kms-v3d,cma-512              Comment out this line
#dtoverlay=vc4-kms-v3d-pi4
#dtoverlay=vc4-fkms-v3d                          Uncomment this line
max_framebuffers=2
arm_boost=1
#disable_fw_kms_setup=1

As I understand it this forces the use of an older display driver.

I believe this problem was due to an incompatability between the display I was using (Cheap Chinese 10 display) and the newest driver on the RPi. Forcing it to use the older driver got it working perfectly.

BTW, I also tried the same SD card on my son's RPi 5 and had no problems even with the unmodified config.txt.

Incidentally, the display I was using is a cheap one I use as a second display when I travel for work. I bought cheap because it is likely to get busted up in luggage some day. For my final LinuxCNC display I will be using a different touch screen display. Hopefully that one will work well.

I hope this will be helpful to anyone who may encounter the same problem.