Display Hat Mini and Pi4B

Support
1

Hi All,
A plea for help. I have so nearly got this working. Any pointer for what I should try next would be very greatfully received.
I have been following the wonderfully well explained instructions here…

All goes well until the final step where I get the message “vc_dispmanx_display_open failed! Make sure to have hdmi_force_hotplug=1 setting in /boot/config.txt”
And I do have.

Thanks!
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Full message…
pi@raspberrypi:~/fbcp-ili9341/build $ make -j
[100%] Built target fbcp-ili9341
pi@raspberrypi:~/fbcp-ili9341/build $ sudo ./fbcp-ili9341
bcm_host_get_peripheral_address: 0xfe000000, bcm_host_get_peripheral_size: 25165824, bcm_host_get_sdram_address: 0xc0000000
BCM core speed: current: 200000000hz, max turbo: 500000000hz. SPI CDIV: 40, SPI max frequency: 12500000hz
Allocated DMA channel 7
Allocated DMA channel 1
Enabling DMA channels Tx:7 and Rx:1
DMA hardware register file is at ptr: 0xf6047000, using DMA TX channel: 7 and DMA RX channel: 1
DMA hardware TX channel register file is at ptr: 0xf6047700, DMA RX channel register file is at ptr: 0xf6047100
Resetting DMA channels for use
DMA all set up
Initializing display
Setting TFT backlight on at pin 13
Creating SPI task thread
InitSPI done
vc_dispmanx_display_open failed! Make sure to have hdmi_force_hotplug=1 setting in /boot/config.txt

1 Like
2

PS
The example programs all work fine.

My objective is to use the display as a ‘monitor’ for a camera using Pi Zero 2 W along with a Pi Camera Module 3. All 3 bits of kit seem to be wonderful and would be grat if they all worked together!

3

Make sure its as above and not
#hdmi_force_hotplug=1

4

Many thanks for the reply.
I have tried un-commenting the line mentioned.

Actually, when I do that, the HDMI display stops working and I have to use VNC viewer to restore it. Maybe that is a clue?

5

I “think” when its uncommented it stops auto detection of your monitor? Its supposed to let your system boot headless with no monitor attached to HDMI. It makes Pi OS think there is a monitor connected when there really isn’t one connected. Something like that anyway?
Raspberry Pi 4B desktop environment won’t start without monitor attached - Support & Help Requests / Raspberry Pi - Ubuntu MATE Community (ubuntu-mate.community)

6

I have a system composed of a Pi Zero 2W, Pi HQ camera, and the Display Hat Mini and had my project working using the Lite (headless) Pi Bullseye OS and the Picamera Python driver. The CircularIOBuffer was not working correctly with Picamera, so I upgraded to Picamera2. At that point, I started getting the error “vc_dispmanx_display_open failed! Make sure to have hdmi_force_hotplug=1 setting in /boot/config.txt”. Whether that code line is commented out or not, makes no difference.

I am using the fbcp-ili9341 method to “mirror” the display to the Display Hat Mini, and it had been working when my program used Picamera.

The only changes to my system are going from Picamera to Picamera2 and changing the setting in raspi-config concerning the Legacy Camera support.

I am hoping for a revelation here to get me back on track.