Techie resurrects teletext on a vintage BBC Master
- Reference: 1706615111
- News link: https://www.theregister.co.uk/2024/01/30/resurrecting_teletext/
- Source link:
Andrew Hutchings – aka "LinuxJedi" – [1]posted a blog last week to warm the heart of many a retro enthusiast keen to revisit Teletext in its natural habitat: the Mode 7 display on a BBC computer.
Resurrecting Teletext has long been possible, and bringing the service to life on a Raspberry Pi hooked up to a modern television is relatively straightforward. If you want to experience life from the days when having a Teletext-capable television was impossibly glamorous but don't fancy the tinkering needed to make it happen, [2]there's also a site for that .
[3]
But where, frankly, is the blood, sweat, and tears fun in that? And so, we come back to Hutchings and a recreation of Teletext on the screen of a BBC Micro – or, in this case, a BBC Master.
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Hutchings followed the well-worn path of getting Teletext working on a Pi via the 3.5mm audio/video socket – now deleted from more recent incarnations of the hardware – but set about taking the next step: broadcasting the signal and having it picked up by a BBC computer.
[6]At last: The BBC Micro you always wanted, in Mastodon form
[7]40 years since Elite became the most fun you could have with 22 kilobytes
[8]Absolute mad lad renders Doom in teletext
[9]Ceefax replica goes TITSUP* as folk pine for simpler times
Hutchings' Pi, an old Model 3A+ with a fried GPIO due to an earlier experiment, pumped out a composite signal. However, an analog broadcast on a specific UHF frequency was needed. While an RF modulator to do the deed is (relatively) readily available, getting the information into Acorn's finest requires more exotic hardware.
The BBC Micro and Master already have the hardware to render the display, but something extra is required to pipe in the data. Hutchings picked up an old [10]Morley Electronics Teletext Adapter , [11]flashed the necessary ROM , and after a bit of adjustment and coordination with the supplier of the Morley unit, Teletext rode once more on a BBC computer, more than a decade after the BBC killed off Ceefax as part of the digital switchover.
We asked Hutchings why he went for the Morley device rather than [12]Acorn's wedge . He gave us three reasons: "It was cheaper than the Acorn Wedge for me to acquire, it has a digital tuner, which I figured would be easier to work with than blindly twiddling dials, [and] powering from the BBC means I don't need as many 3 pin plug sockets when demoing."
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Fair enough.
Hutchings also told us that he'd now managed to acquire the Acorn device. "There is an advantage to them, which is that you can very easily modify them to use a composite input. But, I haven't tested mine yet, and they have tantalum capacitors inside which tend to short-circuit and explode with age, so I'd want to carefully refurbish it first."
We were delighted with the [14]implementation of Teletext on a Pi and the appearance online of a Ceefax replica. However, Hutchings' work takes that experience to the next level, and, as such, we salute him.
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"It is thanks to the BBC Micro that I learnt how computers work at a low level and can do what I do today." ®
Get our [16]Tech Resources
[1] https://linuxjedi.co.uk/2024/01/25/teletext-on-a-bbc-computer-in-2024/
[2] https://www.nathanmediaservices.co.uk/ceefax/
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/bootnotes&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2ZbkrOS57D8kcoFPQQ6LHsQAAAIk&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/bootnotes&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44ZbkrOS57D8kcoFPQQ6LHsQAAAIk&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/bootnotes&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33ZbkrOS57D8kcoFPQQ6LHsQAAAIk&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[6] https://www.theregister.com/2024/01/18/bbc_micro_bot/
[7] https://www.theregister.com/2024/01/18/elite_game_retro/
[8] https://www.theregister.com/2023/05/31/doom_teletext/
[9] https://www.theregister.com/2022/01/06/ceefax_replica/
[10] https://www.computinghistory.org.uk/det/32517/Morley-Electronics-Teletext-Adapter/
[11] https://www.beebmaster.co.uk/Teletext/UseMorley.html
[12] https://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Acorn_ANE01_TeletextAdapter.html
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/bootnotes&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44ZbkrOS57D8kcoFPQQ6LHsQAAAIk&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[14] https://www.theregister.com/2022/01/06/ceefax_replica/
[15] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/bootnotes&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33ZbkrOS57D8kcoFPQQ6LHsQAAAIk&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[16] https://whitepapers.theregister.com/
Composite Video is still present on the PI
"followed the well-worn path of getting Teletext working on a Pi via the 3.5mm audio/video socket – now deleted from more recent incarnations of the hardware"
The composite video output is still present on the newer PI's, only the analog audio is no more.
e.g. On the PI5 it's an empty pair of holes between the HDMI and Camera/Display ports that you need to solder to - but they are still there and supported
Re: Composite Video is still present on the PI
So a 3,5mm socket that isn't there and you have to solder back on "is still present"
Only in the sense they did an incomplete job of ripping it out and some of the software happens to still be there.
This is the same bullshit where I no longer have a headphone jack in my Android phone and have to use a USB adapter, so I have to choose between hearing my meeting and running out of battery, or charging so I can stay in my meeting, or using a Bluetooth headset that randomly disconnects and is out of battery anyway.
So no, I still only buy 3B+s and won't buy anything newer.
Where's that article on enshittification again?
"Flash"???
I doubt that flash chips even existed when that teletext adapter was originally sold.
However, I do like the various Teletext resurrection projects and it really does give it a little extra something when it's done using period correct hardware.
Re: "Flash"???
The BBC didn't use them back then, and I do often use EPROMs for my BBC computers, but the cartridge I have for this Master 128 uses a flash chip.
"RAM" EPROM
I soldered a couple of 8K RAM chips on top of each other (with a hack for the top address line) and added a switch on the back to give a "writeable ROM"* that made it much easier to develop ROMS - add allowed me to change which one was loaded when the 16-slot extension board I had ran out of spaces.
* it's probably still in the system that's somewhere in the garage.
Re: "Flash"???
It's straightforward to get a machine to read from flash instead of eprom, they're almost pin-compatible. And flash can be reprogrammed without the use a UV eraser first.
Hats off to this fellow for reviving some ancient technology!
Flash?
Some old 486 DIL BIOS ICs are pretty pin compatible with EPROMS/ROMS and are just Flash. Years ago I made an adaptor that took two ICs, one socket the original BIOS IC and the other was the device to be programmed. Boot floppy with Flash chip bin loader for update of BIOS, but put your own file. All the pins except /CE in parallel. Move the /CE jumper after boot and run the update program.
You can program Flash for you own code of Gameboy cartridges (it will run Z80 code), or a channel lookup table to convert a CB or commercial Mobile rig to Amateur bands.
Mine is the one with JEDEC EPROM pinouts in one pocket and Z80 Instruction set in the other.
Re: Flash?
You can actually use a AT28C256 flash chip with BBCs, but you need to flash the data to the top half of the chip. I've done this with AT27C256 before which is the write-once version. It is very easy to create adapters to use things like the SST39Fxxx series too.
Prestel resurrected
Over at https://glasstty.com John created a functional copy of Prestel called Telstar, which could also be viewed on a BBC and looked just like Ceefax. You can even host your own frames on the Telstar service via https://glasstty.com/hosting-frames-on-telstar/
Worth a look if you are feeling geeky!
Fabulous
The Beeb even transmitted BBC computer software (in BASIC, I think) on occasion.
I was never in a position to ‘download’ any as I couldn’t afford the teletext adapter as a spotty 14yo.
There's a nice library of BBC Micro teletext utils here:
https://mdfs.net/System/Teletext/