P2 - HDMI and Waveshare 5" display

Comments

• Wuerfel_21 Posts: 5,763

  2026-01-01 15:41

  Possible issues:

  • Display does not like the pin drive mode used (try replacing the line that says wrpin ##%001001<<8,#7<<6 + hdmi_base 'set 1k-ohm drive on HDMI pins with wrpin ##P_REPOSITORY|P_OE|P_LOW_FAST|P_HIGH_1K5|P_SYNC_IO, #hdmi_base addpins 7
  • Specialty display wants special resolutions (try this on a PC or something - does it actually take 640x480 modes?)
  • Some sort of exciting protocol incompatibility (not sure if chip's example is 100% spec compliant)
• Rayman Posts: 15,951

  2026-01-01 15:50

  What is display resolution?
  Looks like might be 800x480…
  That might require code tweaks
• Rayman Posts: 15,951

  2026-01-01 15:51

  Also it might be the 5v signal. Some displays seem to need it. The parallax adapter needs a jumper wire added to provide that…
• Wuerfel_21 Posts: 5,763

  2026-01-01 15:53

  Oh the 5V pin, that's the No. 1 thing to check actually. Some sinks will not turn on without that. Simple electrical fix.
• Rayman Posts: 15,951

  2026-01-01 16:22

  Here's an example of the jumper wire... Could also be a resistor instead of a jumper, like 1k or so...

  

  

  IMG_5511.jpeg

  480 x 640 - 213K

  IMG_5511.jpeg 212.5K
• Brian_B Posts: 844

  2026-01-01 18:04 edited 2026-01-01 18:04

  1080x1080 , but after i tried It with the 5 volt jumper wire it won't even work on the RPI.
• VonSzarvas Posts: 3,623

  2026-01-01 18:31 edited 2026-01-05 22:46

  The newer rev of the hdmi addon has pads labelled near the hdmi socket for adding a 1k resistor or jumper/shunt.

  BUT… first be sure that your breakout board is outputting 5V at the accessory headers (and not a higher voltage).

  That usually means the breakout is powered by 5V (and not a higher voltage). And also that the breakout board has the 5V outputs enabled.

  To verify, measure the 5V output pin on the breakout board header before attaching the addon.
• Rayman Posts: 15,951

  2026-01-01 19:45 edited 2026-01-01 19:45

  P2 can't drive 1080x1080 HDMI display directly. 800x480 is close to the max.
• Rayman Posts: 15,951

  2026-01-01 21:43

  Suppose there's a chance that a VGA--> HDMI adapter would work. That could signal 1080p which may or may not make the display happy...
• rogloh Posts: 6,215

  2026-01-02 00:49

  @Brian_B said:
  1080x1080 , but after i tried It with the 5 volt jumper wire it won't even work on the RPI.

  Hopefully you didn't damage it in the process by perhaps shorting 5V somewhere it didn't like.

  1080x1080 is an unusual resolution. I'm not sure that cheap VGA to HDMI adapters would do that conversion. You might have to scale down the input from 1920 to 1080 horizontally. But if the 5 inch display simply takes a regular 1920x1080 signal to begin with and does that scaling for you it might be okay. Is that how it works, it scales 1920 down to 1080? Or does it show the centre 1080 pixels of the 1920 horizontal pixels you provide? I've not used these circular displays before.
• potatohead Posts: 10,267

  2026-01-05 18:41 edited 2026-01-05 20:00

  Hey everyone!

  TL;DR: It is well worth trying those converters. Analog video generation on P2 is far more capable of these higher custom resolutions than the digital system is, and that's just due to the 10x bitrate needed for DVI.

  Those adapters seem to translate whatever you do in the analog domain to HDMI fairly well. I can say the same for both directions. I use these devices regularly both directions and have not really seen problems with odd resolutions.

  (CRT talk moved to general discussion)
• Wuerfel_21 Posts: 5,763

  2026-01-05 19:12

  @potatohead said:
  Maybe I will make a post.

  You should really do that instead of threadjacking.
• potatohead Posts: 10,267

  2026-01-05 19:14 edited 2026-01-05 19:59

  Yes I completely agree, and am in process about to come back and edit post above. You beat me by a few minutes.

  All done!