Raspberry Pi5 - two DSI LCD

[Mariossos]

Hello,

I have two DSI LCD 4.3inch:
https://www.waveshare.com/wiki/4.3inch_DSI_LCD

Displays connected using:
https://www.waveshare.com/cm-dsi-adapter.htm

Loaded the latest Raspberry Pi OS (64 bit) onto the SD card.
What do I need to change in the /boot/firmware/config.txt file? After starting the Raspberry Pi5 with two displays connected, the red diode is constantly lit and the system does not start.

[6by9]

Does it work with one display connected? Does it matter which port it is connected to?

It's a third party product that clones the Raspberry Pi display - support should come from Waveshare (I do love Waveshare's anti-piracy and "Beware of knock-offs" sections in the wiki seeing as they copied the Pi design).

As an outside guess, it looks like they're powering the whole display off the 3V3 rail that is present on the DSI FFC connector. That's quite a load, so it's quite possible that it exceeds the current the Pi can provide at 3V3.
The wiki sort of confirms that with

Question: What is the working current of 4.3inch DSI LCD?
Answer:

The normal working current of Raspberry PI 4B alone with a 5V power supply is 450mA-500mA;
Using 5V power supply raspberry PI 4B+4.3inch DSI LCD maximum brightness normal operating current is 700mA-750mA;

So it's adding an extra ~300mA per display, so around 600mA for two displays (ignoring the step down in voltage and conversion losses).

[Mariossos]

If I have a display connected to the CAM/DISP0 port, everything works. Same for the CAM/DISP1 port. Both ports work fine separately.

Everything is powered by the original USB C 5.1V / 5A power supply.

[aBUGSworstnightmare]

What is in your config.txt?
Autodetect of two DSI displays might not work ...

[Mariossos]

Default file:

Code: Select all

# For more options and information see
# http://rptl.io/configtxt
# Some settings may impact device functionality. See link above for details

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

# Additional overlays and parameters are documented
# /boot/firmware/overlays/README

# Automatically load overlays for detected cameras
camera_auto_detect=1

# Automatically load overlays for detected DSI displays
display_auto_detect=1

# Automatically load initramfs files, if found
auto_initramfs=1

# Enable DRM VC4 V3D driver
dtoverlay=vc4-kms-v3d
max_framebuffers=2

# Don't have the firmware create an initial video= setting in cmdline.txt.
# Use the kernel's default instead.
disable_fw_kms_setup=1

# Run in 64-bit mode
arm_64bit=1

# Disable compensation for displays with overscan
disable_overscan=1

# Run as fast as firmware / board allows
arm_boost=1

[cm4]
# Enable host mode on the 2711 built-in XHCI USB controller.
# This line should be removed if the legacy DWC2 controller is required
# (e.g. for USB device mode) or if USB support is not required.
otg_mode=1

[all]

[gordon77]

Does it need something like ..

#display_auto_detect=1

dtoverlay=vc4-kms-dsi-7inch,dsi0
dtoverlay=vc4-kms-dsi-7inch,dsi1

?

[Mariossos]

Unfortunately it does not work. Earlier, I tried commenting auto_detect and adding these two lines.

[6by9]

If I have a display connected to the CAM/DISP0 port, everything works. Same for the CAM/DISP1 port. Both ports work fine separately.

Everything is powered by the original USB C 5.1V / 5A power supply.

In which case it does sound like 2 displays take more current at 3.3V than the Pi5 can supply.
Nothing is going to fix that other than providing some alternative powering mechanism (and do NOT back 3.3V back from your display into the Pi).

[aBUGSworstnightmare]

If I have a display connected to the CAM/DISP0 port, everything works. Same for the CAM/DISP1 port. Both ports work fine separately.

Everything is powered by the original USB C 5.1V / 5A power supply.

In which case it does sound like 2 displays take more current at 3.3V than the Pi5 can supply.
Nothing is going to fix that other than providing some alternative powering mechanism (and do NOT back 3.3V back from your display into the Pi).

+1
As the two displays in question run on 3.3V only (from the DSI interface) incl their backlights. The 3.3V rail of the Pi is not designed for such!

So it's waveshare you need to complain at!

[cleverca22]

it may also be possible to modify that flat-flex adapter board

cut the 3.3v trace, and then add your own 3.3v source to the display side

you could also fab up some custom ones with that change

[Mariossos]

I checked the voltages. 5.1V and ... 0V on 3V3.

[Amarantos]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

[aBUGSworstnightmare]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

[Amarantos]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg (98.91 KiB) Viewed 19401 times

It seems that dual DSI touch screens can be used simultaneously.

[6by9]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

Yes you can use 2 DSI panels simultaneously, but it depends on the powering arrangements for those panels.
If they have external power supplies or take 5V from the Pi then they will be fine. If they use the Pi's 3.3V rail, then it will depend on the panel.

[aBUGSworstnightmare]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

how do you power them as that's not visible?

[Amarantos]

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

how do you power them as that's not visible?

I contacted Waveshare technical support a month ago and they have updated it to be compatible with the pi5 version.
Currently using their 5inch DSI LCD and 4.3inch DSI LCD (maybe Rev2.1/Rev2.2), which are completely powered by the Pi5's mipi DSI interface. No additional power supply is used.

[aBUGSworstnightmare]

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

how do you power them as that's not visible?

I contacted Waveshare technical support a month ago and they have updated it to be compatible with the pi5 version.
Currently using their 5inch DSI LCD and 4.3inch DSI LCD (maybe Rev2.1/Rev2.2), which are completely powered by the Pi5's mipi DSI interface. No additional power supply is used.

so let's keep fingers crossed the also tested two of each at full brightness (if the brightness can be controlled). This method will stop working once people add more electronics to the Pi's 3.3V rail or when they try to power bigger screens like that (TFT inrush current).

No info on the max current that can be drawn from the 3.3V rail known to me.

Think we can conclude that such questions now should be answered exclusively by waveshare (or any other third party) technical support, because nobody here on the form knows which display HW revision will be/is compatible.

[steveiliop56]

Red LED indicates system is not booting/shutdown. Maybe you can try turning it on manually by pressing the start button？

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

Wait how did you get the display to work? I currently have a 4.3 inch that I bought now same problem. Is that a different screen or did you find a way to make it work?

[Amarantos]

that's a good one, but sorry! Of no help at all as the 3.3V rails is overloaded (and thats stopping the Pi from booting).

2-DSI.jpg

It seems that dual DSI touch screens can be used simultaneously.

Wait how did you get the display to work? I currently have a 4.3 inch that I bought now same problem. Is that a different screen or did you find a way to make it work?

Compared with the previous version of the latest version of DSI I have, you can clearly see that several large capacitors are not soldered. Maybe you can try removing the 2-3 large capacitors on the DSI LCD to successfully pass the pi5 power test.

But I only recommend it for personal try and agree with aBUGSworstnightmare, you can contact waveshare technical support https://service.waveshare.com/ to get the most suitable solution.

[steveiliop56]

Well waveshare is stupid! I sent them an email some time ago before buying the screen and they confirmed it works with the pi 5! Now I have to go through the refund process and send it back because of them.

[Amarantos]

Well waveshare is stupid! I sent them an email some time ago before buying the screen and they confirmed it works with the pi 5! Now I have to go through the refund process and send it back because of them.

It can be seen from the picture that the DSI LCD I have is indeed compatible with pi5. What you need to ask is why the version you received is not compatible. Maybe there are some usage details that we didn't notice. Good luck!

[steveiliop56]

Is it possible for you to show me a picture of the back of the screen? So I can compare with my version?

[steveiliop56]

Umm are you still here?

[rasmeanttobe]

I am having exactly the same problem and it does not matter where I search, I cannot find a solution.
Submitted tickets for both the seller and waveshare - although I am very keen on knowing the display model of who made it work and how they made it work, if possible along with the config.txt just to see the lines and try to copy it!

Thanks!!