serial console during boot process

Oct 17, 2026 Last reply: 3 hours ago 3 Replies

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Marco Moock 8 hours ago

Hello!

I have a RPi 4B. I used it with Debian in the past, now I want to use FreeBSD 15.1. I extracted the .xz file and wrote the .img to the disk, the 2 partitions are there.

Although, I only see the rainbow bootscreen.

Now someone suggested that I should look at the serial output.

I connected a TTL to USB adapter. Does this already give output during the boot process (with or without the OS loaded)?

I used this adapter successfully at a Switch, so it is operational, but I need to know which speed/duplex settings the RPi requires during the boot process.

Thanks for any suggestions.

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Theo 7 hours ago

Did you check both HDMI ports? Some OSes only show boot messages on one screen.

I can't comment on this particular OS, but most console outputs these days are 115200 baud 8N1 (8 bits, no parity, 1 stop bit). If that doesn't work, it's almost always 8N1 but you can try other speeds (57600, 38400, 19200 etc).

Theo

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bp 4 hours ago

I've been using FreeBSD-current and -release on RPi4Bs for some time now, they seem to work faultlessly. I'm tempted to suggest a different image file. The serial console has been active without any obvious intervention on my part.

For serial consoles I use tip on the terminal host, with the line ucom:dv=/dev/cuaU0:br#115200:pa=none: added to /etc/remote.

hth,

bob prohaska

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Daniel 3 hours ago

What a fantastic idea. I've been connecting the pi's to a screen and keyboard during initial config. Didn't ever think to get a ttl adapter for headless config. Sometimes I wished I could. Now I have incentive to get gentoo on my 3b+ since freebsd 14.5 doesn't support the audio chip on that board.

I love usenet.

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