Waveshare 7''' HDMI LCD (C) not working with Raspberri Pi 4B

[Taliken]

Hello,

I’m encountering trouble with my new Waveshare 7inch HDMI LCD display. I got it originally to connect to my Raspberry Pi 4B, purchased a few weeks ago, and, well, I shall just describe what happened.

OS: Raspbian 10 Buster

The Pi 4B in question has been used before with an iiyama (I think) HDMI-screen to install Raspbian from NOOBS, and worked without problems.

Followed tutorial https://www.waveshare.com/wiki/7inch_HD ... spberry_Pi to the letter, including adding five lines to config and outcommenting one. Since it does say the display can be used with the Pi 4B, it shouldn‘t be an incompatibility issue.

Turned on power, screen remained black. Tried to shut down by using CTRL+ALT+T and blind-typing "sudo halt", but system would not shut off. Instead the green light started blinking, four short, one long.

Disconnected from power, swapped HDMI cable and USB-connector cable thinking one might be broken. Also swapped outlets and USB-ports. None of the different configurations worked.
Note: Since the Pi 4B has the smaller HDMI outlet, I couldn‘t use the HDMI noodle cable that comes with the screen, but instead used the official 4B HDMI cable that came with the Pi 4B starter kit. The second HDMI cable I used was is also an offical cable, the USB-connector cable was not.

Next attempt at powering on failed as well, but this time my Pi also did not even blink green anymore, I got one green flash, then only the red LED remained on.

Removed SD-card, put it into Raspberry Pi 2B, which is connected to the offical Touchscreen Display to see if the card was corrupted. It booted normally. Connected Pi 4B to official Touchscreen to see if that one was broken, with the same SD-card. It booted normally.

Attached Raspberry Pi 2B to Waveshare LCD display, used same SD-card. Boot went fine, display works well. Tried once more with Pi 4B, and this time it made it as far as "Welcome to Pixel Desktop", then the whole thing froze and I had to cut power to turn it off.

Luckily, it appears the Pi 4B wasn‘t fried, because it‘s still working with the official touchscreen display. It is, however, not working with the Waveshare LCD Display. I spent about an hour googling and reading up about possible issues, but couldn‘t find an answer beyond "SD-card might be corrupt" (which it is not, as it boots fine as long as it‘s in the Pi 2B) and "forgotten to edit config.txt", which also doesn‘t apply.

Any other ideas as to what might be wrong are welcome, and if you need any more software information, please post the command that will provide the necessary information. I‘m not a total newbie to Linux, but I don‘t do a lot of analysing my OS, so will likely not know which command to use to get the required information for you.

Thanks a lot in advance!
Tal

[gamblor999]

Hey there, looks like waveshare have posted a solution for the raspberry pi 4B here

https://www.waveshare.com/wiki/5inch_HDMI_LCD

[aBUGSworstnightmare]

Hey there, looks like waveshare have posted a solution for the raspberry pi 4B here

https://www.waveshare.com/wiki/5inch_HDMI_LCD

that's not 'a solution'! As the simply recommemd to use legacy driver instead of FKMS --> no more HW acceleration if one follows that recommendation!
They would better offer a EDID file instead!

[mooblie]

Just something to check: you haven't accidentally switched off the backlight?

[Taliken]

Hey there, looks like waveshare have posted a solution for the raspberry pi 4B here

https://www.waveshare.com/wiki/5inch_HDMI_LCD

Thanks, I’ll check that out in the next few days when I have a moment to spare.

Just something to check: you haven't accidentally switched off the backlight?

Nope, definitely not. After I put it in the right position, I didn’t touch it again save for the one time I switched it off and then on again, thinking that maybe I had failed to move it into position properly.

In the meantime, I have switched the boards I used with the screen around a few times, and can now report that it works just fine and without a hitch with two different 2Bs, two 3Bs and one 3B+, and different SD-cards. So … yeah. I’ll have a look at the solution Waveshare has posted and see what happens.

Anyhoo, thanks

[gamblor999]

I got my Waveshare 7inch (C) working by following the instructions listed here:

https://www.opendisplaycase.de/tutorial ... touch.html


Let me know if this helps you.