Close
0%
0%

Teletext display

Teletext is dead, but there are many teletext chips that can still be useful as displays for embedded projects

Similar projects worth following
This project started as a teletext receiver for the PC, in the days when you could bit-bash the printer port. Circa 2000! I got some DOS code bit-bashing I2C, but got distracted by work! Analogue TV switched off, and it became junk.

Then some hobbyists said they wanted text output on their projects. An easy and cheap way to get coloured 40-column text and block graphics on any project is to make use of the large stock of obsolete and cheap teletext chips.

At the moment I have an SAA5246 in DIP48, a 27 MHz crystal and an 8K RAM, which is enough to start the project. It is the L font option but I can live with that for now.

There is a chip with an amazing feature list - the SDA5273 - but I think it will be hard to program and there is no programming guide for it on the internet.

My first thought was to use the MV1815, a chip I had used before.
It needs a 27.75 MHz crystal which is not common.
I got a quote to get them made, for about £140 set-up charge and about 20p per unit. Not impossible but not cheap either.

Googling teletext chips, I found the SDA5273 which seems to be one of the very last - and advanced - chips made before digital TV effectively halted teletext technology.

https://www.ebay.co.uk/itm/4pcs-SDA5273-2PGEG-SDA5273-Teletext-MEGATEX-Ics-PLCC84-MICRONAS/263383835491

Suitable DRAM chip:

https://www.ebay.co.uk/itm/HM514400CS6-Hitachi-DRAM-1-048-576-Word-x-4-bit-20pin-SOJ-DRAM-4-PER-SALE/222248086779?epid=1548393060&hash=item33bf04acfb:g:cwcAAOSwFe5X1sr6

And 20.48 MHz or 8 MHz crystal, depending on which data sheet you read.

Features:

● Single chip teletext IC
● Stores up to 14 teletext pages on chip
● Stores up to 2048 teletext pages with external 16 M memory
● Analog RGB-output
● 41 latin script languages
● 12 × 10 character size
● Parallel display attributes
● 64 from 4096 colors selectable
● Enhanced flash modes
● Dynamically redefinable character set (DRCS, PCS)
● Pixel graphics
● Fullscreen display (64 × 32 or 80 × 24 character positions)
● Horizontal and vertical scrolling
● Graphic cursors
● 4:3 and 16:9 display
● Multinorm display (50/60/100/120 Hz)
● RISC-processor
● Firmware downloadable
● I2C / 3 wire UART-interface (1 Mbit/s)
● Independent clocks for acquisition and display
● Tools for greatly simplified software development
● P-LCC-68-1
● P-SDIP-52-1
● 24-Kbyte on-chip reconfigurable DRAM
● 44160-bit character ROM
● One external crystal for all standards

Teletext Features:

● Analog CVBS-input with on-chip clamping circuitry
● Data Slicer
● Supports level 1, 2.5 and 3.5 ETSI teletext standard
● full level 2.5 processing

See 

https://en.wikipedia.org/wiki/Teletext

https://www.etsi.org/deliver/etsi_i_ets/300700_300799/300706/01_60/ets_300706e01p.pdf

At the moment, I'm inclined to use the SAA5246, because it is simple and there is code for it on the web.

I have removed the tuner module (which was dead anyway) to make room for the new circuitry.

  • Hardware

    Keith04/01/2019 at 23:30 0 comments

    2019-04-01

    Parcel of goodies arrived including MV1815 and SDA5273 chips. I removed the dead chips and fitted new a new MV1815 and 64Kx4 DRAM chip. The phono socket used to be the UHF output from the tuner. As the analogue tuner was dead and obsolete, it has been removed. The phono socket can now be the video input to the teletext chip. The MV1815 outputs are red, green and blue, and will be routed to the RGB input pins of a SCART socket. This project will require a SCART-socketed colour TV, which I have.

    I gave some chips to a workmate to play with. They might be useful as text overlay chips, but all the monitors at work are baseband monochrome. A few colour LCD monitors have SCART inputs. But there are obsolete analogue colour TVs available cheaply on ebay - collection only, they are too heavy to post.

View project log

Enjoy this project?

Share

Discussions

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates