Ewal
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Tv-out does not work with USB boot

Wed Jun 09, 2021 11:31 pm

So I had a 7" car lcd that I wanted to make a little portable game machine with. I got a 60gb ssd for quick loads and discovered that the pi wont boot from usb with enable_tvout=on in the config.txt file. If I delete it, it will boot, even # in front of it will stop the boot, needs to be totally deleted. Just to check I used a microsd and it works like a charm, just MUCH slower boot times, anyone have any ideas?

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rpdom
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Re: Tv-out does not work with USB boot

Thu Jun 10, 2021 7:30 am

Very odd. There's a few more things I would try:

* Note the size of the file (in bytes) before and after making the changes.

* Try misspelling the option, maybe enable_vtout=on, or something.

* Replace it with something completely different.

* Change which line of config.txt it is on

* Copy the config.txt to a new file. Delete or rename the old file. Rename the new one to config.txt

I'm thinking it might be some buffer size limitation somewhere. I could be wrong.
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thagrol
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Re: Tv-out does not work with USB boot

Thu Jun 10, 2021 8:37 am

Odd indeed. Can you confirm which model Pi you're using.

I'd also try the "hybrid" approach: /boot on SD, / on SSD.

In brief and assuming a 4B and only one USB drive:
  1. You may need to change boot order in the EEPROM to prioritise SD card over USB.
  2. On the SD card change /boot/cmdline.txt to use root=/dev/sda2
  3. On the SSD change /etc/fstab to use /dev/sda2 for "/" instead of the PARTUUID.
  4. On the SSD change /etc/fstab to use /dev/mmcblk0p1 for "/boot" instead of the PARTUUID.
Backup the existing files before you change them.
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thagrol
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Re: Tv-out does not work with USB boot

Thu Jun 10, 2021 8:48 am

A further thought occurs: it might be related to conditional filters in your config.txt if you have any.
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Ewal
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Joined: Wed Jun 09, 2021 11:24 pm

Re: Tv-out does not work with USB boot

Fri Jun 11, 2021 1:22 am

It is a pi 4B fully updated. It just flashes green like it is missing boot drive only when the enable TV out is in the config file, it is very strange

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B.Goode
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Re: Tv-out does not work with USB boot

Fri Jun 11, 2021 8:04 am

Ewal wrote:
Wed Jun 09, 2021 11:31 pm
So I had a 7" car lcd that I wanted to make a little portable game machine with. I got a 60gb ssd for quick loads and discovered that the pi wont boot from usb with enable_tvout=on in the config.txt file. If I delete it, it will boot, even # in front of it will stop the boot, needs to be totally deleted. Just to check I used a microsd and it works like a charm, just MUCH slower boot times, anyone have any ideas?

Out of curiosity, I read the supporting documentation -
Ref: https://www.raspberrypi.org/documentati ... t/video.md
enable_tvout (Pi 4B only)
On the Raspberry Pi 4, composite output is disabled by default, due to the way the internal clocks are interrelated and allocated. Because composite video requires a very specific clock, setting that clock to the required speed on the Pi 4 means that other clocks connected to it are detrimentally affected, which slightly slows down the entire system. Since composite video is a less commonly used function, we decided to disable it by default to prevent this system slowdown.

To enable composite output, use the enable_tvout=1 option. As described above, this will detrimentally affect performance to a small degree.


Maybe the clock slow-down is sufficient to break the usb mass storage functionality?

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davidcoton
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Re: Tv-out does not work with USB boot

Fri Jun 11, 2021 9:18 am

B.Goode wrote:
Fri Jun 11, 2021 8:04 am
Maybe the clock slow-down is sufficient to break the usb mass storage functionality?
Or maybe it's the difference between "=on" and "=1", though I thought invalid lines in config.txt were ignored.
And I have no idea why a commented line would prevent booting.
I think there is more to discover here.
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thagrol
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Re: Tv-out does not work with USB boot

Fri Jun 11, 2021 11:10 am

davidcoton wrote:
Fri Jun 11, 2021 9:18 am
I think there is more to discover here.
Seconded.

@OP: post your config.txt
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