PaulRid
Posts: 3
Joined: Fri Nov 10, 2017 2:00 pm

CM3 HDMI output differences to CM1

Fri Nov 10, 2017 2:36 pm

Hi, I'm wondering if anybody can shine any light on an issue that I am having at the moment?

I have a raspberry pi that connects to a non-standard display. By non-standard, I mean that the display is not an ordinary display but it does support HDMI 1920x1080 @ 60hz.

Previously we have used the CM1 which is working fine with the device. I thought I would be able to reuse the config.txt from this image (Raspbian Jessie Lite) with the new image (Raspbian Stretch Lite) but it will not output anything on the disaply. It is worth noting that if I use a standard monitor then it displays fine.

I have used a video test instrument to verify the video timings and the two devices appear to be identical. The config.txt is not overly complex. These are the main parts of the HDMI configuration:

disable_overscan=1
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
config_hdmi_boost=4
hdmi_ignore_edid=0xa5000080
hdmi_cvt 1920 1080 60

I know that the display does work as it works fine with the CM1 image. Does anybody have any ideas as to why it may not be working with the CM3? Any help or advice would be much appreciated.

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 18199
Joined: Sat Jul 30, 2011 7:41 pm

Re: CM3 HDMI output differences to CM1

Fri Nov 10, 2017 4:24 pm

I wonder if this is a power issue. The CM3 does require more power to run than the CM1, perhaps it means the HDMI is running lower than it should be.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Please direct all questions to the forum, I do not do support via PM.

PaulRid
Posts: 3
Joined: Fri Nov 10, 2017 2:00 pm

Re: CM3 HDMI output differences to CM1

Mon Nov 13, 2017 9:56 am

Thank you for the reply. I went back to check this and I retried the old Raspbian Jessie Lite image on the CM3. This does actually output on the display I was talking about so I think this may be a Stretch Lite issue and not a CM3 issue. Apologies but it looks like this is now in the wrong forum (with an incorrect title). Appreciate the time you've taken to respond.

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