405 lines from Raspberry Pi 5

[Mike Watterson]

I'm running Ubuntu Mate ARM64*. If I mess up I can edit the SD card files  on my laptop or workstation as they both run Linux Mint. Without a 405 monitor, or if your 405 mode is broken you can only fix it by editing the SD card on a different Linux box. Mac and Windows can't read/write ext4 format filesystem, unless someone has a driver. I do have ext2 on my old XP laptop.

I've also a backup of the Pi SD card.

[* on the Pi, but it's only a 4B, so the update/patch likely isn't suitable]

Frank, if you have a PC or laptop with Linux you can edit text files on the Pi SD card. But that update is to the Kernel, so you need to backup the card before applying it and it might be a one way trip.

So having more than one card booting is good. A USB SD card reader will also let you edit text files on one card on the Pi when you boot from a regular one.

[OldTVEnthusiast]

I might be able to throw a little light on this as I kicked off the request on the Pi forum. We use a lot of Pi’s, mainly 3Bs and 4s in a commercial product, and therefore took a lot of interest in the launch of the new Pi 5, which represent a a bit of a quantum leap in performance with only modestly higher costs. I saw a pre-launch video on You Tube discussing the merits of the new custom io hardware designed by the Raspberry Pi foundation called RPi, in the video they made a passing comment that this would enable even obsolete video standards to be output directly. So as soon as I got my hands on a Pi 5 I asked ‘how?’ Dxpecting this to be a line or two of raspian to set the output. The RP engineers explained it wasn’t quite that simple but immedietly offered up a kernel that had a405 and subsequently a 819 option available both from config and the gui. Both work very well. And I understand will be included in the next release of Pi Linux for general release.

Because of lack space on the new board, the Pi5 lost its video out jack but video is available on a two pin header. I think I’ve probably disappointed the Raspberry Pi Engineers in Cambridge who were probably expecting a great You Tube first video to go up showing a Pi 5 outputing to an old Pye (both natives of Cambridge!). Unfortunetly I’ve only managed a few seconds of video on a Sony or two. Pressures of work and family and the fact that the only Pye I have awaits restoration!

So there is a challenge… who can get the first You Tube vid of Pi on Pye posted as a reward to the guys at Pi foundation for implementing this for what is a very select market!

And talking of lack of time, I’ve also a lack of time to design a simple Hat for the Pi 5 that picks up the video from the 2 pin header, sound from and a i2c from the 40pin header and features a couple of modulators. Voila, 819 lines, 405, anything else more esoteric that we can persuade the pi guys to implement and a simple app to select frequencies and standards. Probably little more than an evenings work for those with a touch of genius like Frank C!

[OldTVEnthusiast]

Correction. The new chip is called RP1 and this is why the capability for different video standards can be implemented in Cambridge rather than relying on Broadcom.

https://hackaday.com/2023/10/16/why-the-...ever-made/

[`FRANK.C]

Hi OldTVEnthusiast
Welcome to the forums.
Thanks for taking the time to join and giving us the history of how this great project started.

I know little about the Pi. At the moment I cant even get it working properly. I am getting great help with it from the guys on the raspberry Pi forum. I have it now working OK if booted to console but it wont work on 405 lines when in GUI mode. Hopefully soon we will get it sorted.

Most TV's I have are not restored. Like yourself lack of time is the problem.
I have one Pye that may have been restored before it came into my possession

Frank

[ppppenguin]

Hi @OldTVEnthusaist and welcome to the Golborne forum.

Do you know if the flexible TV standards support was deliberate or just a fortunate side effect of the new design?

[OldTVEnthusiast]

Thanks for the welcome!

Here is the video of Ben Upton talking about the Pi5 RP1 capability. At about 30:30 they talk about video out and Ben gives mention to Baird and Farnsworth.

https://youtu.be/ZswAW9A6wNE?si=aCPGPOeJSBWV9RxT

I think the answer to the accidental/intentional question is more one of they will do it because they can! It’s their own hardware and they write the drivers, and the guys that do all of this are accessible on a forum and want to make it happen. And perhaps something to do with the Raspberry Pi foundations charitable status and the sort of people who work in such an organisation.

Frank, does the gui switch modes ok and get as far as asking if you want to make the change permanent? I remember that at one point I had to start afresh with a new image as the gui options disappeared after an update.

[`FRANK.C]

Frank, does the gui switch modes ok and get as far as asking if you want to make the change permanent? I remember that at one point I had to start afresh with a new image as the gui options disappeared after an update.

The GUI works normally.
But the vintage standards don't appear in screen configuration. Only the normal ones can be seen.

kmsprint -m will list the vintage standards.

To get it to boot to 405 lines in console mode I added video=Composite-1:544x380i  to cmdline.txt
As far as I understand that should make it boot to 405 in GUI mode as well.
If I boot to GUI I get 2 to 3 seconds of 405 at startup (before the GUI appears) then it returns to 625 and also at shut down at the very end there is about a second of 405.

Frank

[ppppenguin]

They certainly mention old TV standards (we'll forgive them saying 425 - it's a long way from their main expertise) but it's a question of how they implement them. As Frank has found with his flexible converter, it's no problem making the H and V counter chains fully programmable. Doing the vertical syncs flexibly to meet all standards is more complex. Doing flexible colour coding is pretty easy, except for SECAM which is utterly different.

PS: @OldTVEnthusaist do you have one of those HMV 902 sets as shown in your avatar? Even by pre-war TV standards they are very rare.

[OldTVEnthusiast]

Frank, I looked at your latest post on the Pi forum and I think you are probably right to assume that the latest version of Raspian has introduced an incompatibility with the pull that enabled the 405/819 resolutions. Hopefully the pi guys will be on it soon and get a solution for you. It doesn’t look like the Pi Imager offers earlier versions of Raspian so not a simple ‘start again’ solution.

[`FRANK.C]

I believe the older versions are available here.

I just need to figure out how to download and mount an older version on a SD card manually.
If I can do that I think it would be worth trying.

Frank