Wakeup HDMI display from standby without interrupting blank screen

Question

I've a HDMI display attached to a RasperryPi 4. After few minutes, first a blank screen is activated, then the display goes into standby.

I want to wakeup the display from standby (by a sensor via bash script) but don't interrupt the blank screen.

I know wakeup is possible with:

DISPLAY=:0.0 xset dpms force on

but is also interrupts the blank screen.

Answer 1

Try using the CEC library and issue:

echo "on 0" | cec-client -s

To install:

sudo apt update
sudo apt full-upgrade
sudo apt install cec-utils

(Note I've followed the RPF guide using full-upgrade but see here for a discussion on upgrade vs full-upgrade)