I'm attempting to get an Elecrow 7" HDMI LCD touchscreen (Amazon UK) to work with my Raspberry Pi 3 B+. Upon following the instructions enclosed with the screen, all I see is "No Signal".
The instructions state that I should add the following to the end of
max_usb_current=1 hdmi_group=2 hdmi_mode=1 hdmi_mode=87 hdmi_cvt 1024 600 60 6 0 0 0
This does not work. I've replaced the whole of
config.txt with just the above: still doesn't work.
I've tried it with just the following:
hdmi_group=2 hdmi_mode=87 hdmi_cvt 1024 600 60 6 0 0 0
That is: no
max_usb_current (apparently not required for the 3 B+), and remove the duplicate
hdmi_mode line. I also double-checked whether the missing
= was a typo in the docs. Apparently this line works with either. I've tried both.
Still no luck.
If I boot with
hdmi_safe=1, then the screen displays, but only at 592x448, rather than the expected 1024x600. The screen works fine at the expected resolution when plugged into a laptop.
I'm trying this with "RASPBIAN STRETCH WITH DESKTOP", Nov 2018, from https://www.raspberrypi.org/downloads/raspbian/.
What am I doing wrong?
Update: It turns out that I had a spare official Pi PSU (5.1v, 2.5A) tucked away in a drawer. Using that almost works:
- Power on the Pi with the screen powered from the Pi: No Signal.
- Power on the Pi with the screen not powered from the Pi: it works. If I then connect the USB cable between the screen and the Pi: it continues to work.
If I power the screen separately from the Pi, the touchscreen stops working. Moreover, if I then unplug the power from the Pi, it appears to draw power backwards from the screen, which seems ... wrong.
Looking back in Slack history at work, it appears that I successfully had the screen working, in text mode at least, back in August, so maybe something broke between (presumably) the 2018-06-29 and 2018-11-13 releases.