Raspberry Pi Forums

Posted: **Wed Aug 29, 2018 1:10 pm**

Hello everyone, we are trying to connect the HDMI output of the CM3 I/O Board to a 5 inch 40 pin display trought Adafruit HDMI to TFT Decoder Breakouthttps://www.adafruit.com/product/2219 but if we configure raspbian /boot/config.txt file like Adafruit instruction, the display doesn't work, only show white backlight flickering.
We can use it with normal Raspberry pi 3 without any troubles and if we connect the I/O board to a standard PC monitor it works.

Does anyone had the same trouble?

Thanks a lot from Elia and BRIAN!

Posted: **Thu Aug 30, 2018 7:59 am**

Hi,
should work flawlessly, so please post your config.txt here to avoid that we Need to use our crystal balls.

You may want to test with below settings for config.txt

Code: Select all

# Switch to DVI driving mode
hdmi_drive=1
# force hotplug and ignore EDID (there's an EDID EEPROM on your board)
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080

# cofigure framebuffer to correct resolution for 5in display
framebuffer_width=800
framebuffer_height=480

# custom Timing for adafruit 5in TFT
# note: tested/used this with the DPI Kippah, but should work with TFP401 too
hdmi_group=2
hdmi_mode=87
hdmi_timings=800 0 40 48 88 480 0 13 3 32 0 0 0 60 0 32000000 6

Posted: **Thu Aug 30, 2018 9:34 am**

Hi, we tryed to use your configuration but nothing changed!

this is our config for the HDMI output (same as Adafruit datasheet):

Code: Select all

# uncomment if hdmi display is not detected and composite is being output
hdmi_force_hotplug=1
 
# uncomment to force a specific HDMI mode (here we are forcing 800x480!)
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0

we have tryed the same configuration on a Raspberry Pi 3 and on that board all works fine.
We suppose that there is a hardware problem on the Compute Module 3 or I/O board.

Our screen is flickering and no image is shown.

Posted: **Thu Aug 30, 2018 12:34 pm**

elius94 wrote: We suppose that there is a hardware problem on the Compute Module 3 or I/O board.

By the way ... do you have a CM3 (on-board eMMC) or a CM3L (boot from uSD Card) and which IO-board do you have?
You've mentioned your IO-Board + CM3 works fine when connected to a standard monitor, so why should it be damaged?
You've also mentioned your 5in display works with a RPi3.

So, assuming you're using the same HDMI cable for all your tests why should your board be damaged? There is either a problem with your LCD display connection (I've had one of the TFP401 boards my self; the FFC connector is garbage!) and/or your settings. Are you using the same uSD for both Systems (assuming you have a CM3L)?

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