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I have a DPI screen with an interface, I have setup DPI on the pi following this guide: https://www.raspberrypi.org/documentation/hardware/raspberrypi/dpi/README.md

I am getting an image but the colours are off. In fact it looks like no Blue and green is displaying as yellow

enter image description here Actually, if I swap B and R in the magic number, then Blue displays as Blue and Red is missing. I think this is better even though it is using the wrong colour order but it seems that red is missing and green is still yellow

enter image description here

Any ideas on where to start with troubleshooting? It's a bit strange that an entire colour can be missing.

These are my settings

dtoverlay=dpi18
#overscan_left=0
#overscan_right=0
#overscan_top=0
#overscan_bottom=0
#framebuffer_width=800
#framebuffer_height=480
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=0x7f226
dpi_timings=720 0 15 15 15 720 0 10 10 10 0 0 0 60 0 35113500 6
4
  • Photographer in me says ‘check the cabling’ as a colour is missing - You May want to edit the question and provide links to the actual board.
    – user115418
    Jun 17, 2020 at 15:59
  • The board is one I designed and had made. I have two of them fully assembled and get the same results on both of them. I've just double checked with a multi-meter between the FPC connector and the IDC header and all the red pins are going where they should point to point Jun 17, 2020 at 16:44
  • Possible clash between the magic number and the overlay? As the overlay controls the pin mode maybe this is not being set correctly for you?
    – user115418
    Jun 17, 2020 at 18:40
  • Thanks, that got me in the right direction Jun 17, 2020 at 19:17

1 Answer 1

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Turns out that as mentioned in this post (and initially suggested by Andyroo), dtoverlay=dpi18 doesn't actually set the pins up, so the following needs adding to config.txt for mode 6

gpio=0-9=a2
gpio=12-17=a2
gpio=20-25=a2

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