[Raspberry Pi 5 / Bookworm] No signal on TV when booted while TV is powered off (External Timer setup)

1

I am running into an issue where my display shows “No Signal” after a scheduled reboot, and I would appreciate your help or advice.

Environment:

  • Hardware: Raspberry Pi 5

  • OS: Raspberry Pi OS (Bookworm / Wayland)

  • Software: Anthias (Version: 2026.07.0)

  • Display: Panasonic TV

Setup & Problem:

  • The TV power is controlled by an external hardware timer.

  • The Raspberry Pi is scheduled to reboot via cron at 7:00 AM every morning, which occurs before the external timer turns on the TV.

  • When the TV powers on via the timer, it displays “No Signal” and the Anthias digital signage interface is not shown, even though the Pi itself has finished booting and is running normally.

What I have tried so far:

  1. Confirmed via SSH that the Pi is fully running (HDMI-A-1 status shows connected).

  2. Added hdmi_force_hotplug=1 to /boot/firmware/config.txt (didn’t fix the issue on Pi 5 / Bookworm KMS).

  3. Added video=HDMI-A-1:1920x1080@60D to /boot/firmware/cmdline.txt to force HDMI output. The kernel log shows [drm] forcing HDMI-A-1 connector on, but the TV still shows “No Signal” when turned on later.

  4. Dumped the TV’s EDID to /lib/firmware/edid-panasonic.bin and configured drm_edid_firmware=HDMI-A-1:edid-panasonic.bin in config.txt.

It seems that when the TV turns on after the Pi has already booted, it fails the HDMI handshake because the Pi is not sending an active signal refresh or the TV doesn’t detect a new connection.

Question: Is there a reliable way or recommended configuration in Anthias / Bookworm (KMS/Wayland) to keep forcing active HDMI output, or to trigger a display re-handshake so the screen displays properly when the TV turns on via the external timer?

Thank you in advance for your guidance!

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There is a fix in fix(viewer): recover Wayland headless-boot display wedge (bounded restarts) by vpetersson-bot · Pull Request #3240 · Screenly/Anthias · GitHub that should help with this.

Generally speaking, we wouldn’t recommend a nightly reboot. Frankly, it is likely to cause more problems that it solves.

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@watanabe, following up, because there is a better answer for this now than the boot fix I linked.

You can drop the external timer. 2026.08.1 added Settings → Display schedule, where you set an on time, an off time and the days of the week. The Pi stays powered and keeps the HDMI link up, and Anthias switches the Panasonic on and off over HDMI CEC at the times you pick.

That also removes the failure you hit. The “No Signal” comes from the Pi booting while the TV is dark, so it has no display to attach to at boot. If the Pi is never rebooted into a dark TV, the problem does not arise. Two changes:

  1. Turn on the display schedule and set it to your opening hours.
  2. Drop the 7:00 AM cron reboot. With the schedule doing the work there is nothing left for it to fix.

Worth checking that CEC is enabled in the TV’s menu first. Panasonic calls it VIERA Link. After upgrading, the System Info page has a “Display Power (CEC)” card: if it reads True or False, CEC is reaching the TV.

Docs: Display Schedule | Anthias