Subj : Re: Releasing the TV before shutting down ?
To   : R.Wieser
From : Joerg Walther
Date : Fri Aug 02 2024 12:34:41

R.Wieser wrote:

>Although you did not mention it, I take it you picked up on that just
>disabeling HDMI output doesn't cause my TV to switch back to its previous
>input.  Which means that that vcgencmd doesn't seem to be the sought-for
>solution (and nullifies the need to test it).

I just asked ChatGPT if it knew an answer, and it did (not that I am
certain if it works):

Yes, it is possible for a Raspberry Pi to send a signal to a TV to
switch the HDMI input before shutting down. This can be done using CEC
(Consumer Electronics Control), a feature available through HDMI that
allows devices to communicate with each other and exchange basic control
commands.

Here’s how you can do it:

Check if the TV supports CEC: Not all TVs support CEC, and it may be
branded under different names like "Anynet+" (Samsung), "BRAVIA Sync"
(Sony), "Simplink" (LG), etc.

Install CEC tools: On the Raspberry Pi, you can install the cec-utils
package, which includes a tool called cec-client. This tool allows you
to send CEC commands.

bash
Code kopieren
sudo apt-get update
sudo apt-get install cec-utils
Send CEC commands: You can use cec-client to send various commands to
the TV. For example, to instruct the TV to switch to a different HDMI
input, you can use specific CEC commands.

Create a script: You can create a simple script that sends the CEC
command when the Raspberry Pi is about to shut down. For example:

bash
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#!/bin/bash
echo "as" | cec-client -s
The command echo "as" | cec-client -s tells the CEC client to switch the
active HDMI source.

Execute the script on shutdown: To automatically run the script when the
Raspberry Pi shuts down, you can add it to the /etc/rc.local file or
create a Systemd service.

Keep in mind that the exact commands and setup may vary depending on
your TV model and the supported CEC functions. It's a good idea to refer
to your TV's manual for specific information about its CEC support.

-jw-
--
And now for something completely different...

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