[BBC-Micro] Ground Control "UTA" teletext adapter -- technical docs?

Philip Pemberton philpem at philpem.me.uk
Fri Jul 31 16:47:46 BST 2009


Hi guys,

I've got a Ground Control / Solidisk "Universal Teletext Adapter" (I 
think it's the earlier UTA-1) kicking around, and given the recent talk 
about TTX, I figure it might be worth trying to make it work again. 
Thing is, the only machine it ever worked on (my RiscPC) is sitting in 
the loft and I really don't feel like dragging it down here and rewiring 
everything to make it work again...

What I'd like to do is tie the thing to one of my Linux boxen, and use a 
USB-to-I2C converter to talk to it, transfer pages to my PC and just 
generally play with it. I've got a pinout for the UTA itself (it's 
archived on Google Groups at 
<http://groups.google.co.uk/group/comp.sys.acorn.hardware/msg/f8605dc99ec13aa8?hl=en&dmode=source>, 
posted by a certain "Richard Murray" back in November 1996) which 
includes an overview of the mainboard, including chip part numbers. 
Basically it's a Mullard tuner, SAB3036 tuner control IC (CITAC), 
TDA8341 IF amp/demodulator, TBA120U audio demodulator, SAA5231 
dataslicer, and an SAA5240P/A Teletext decoder.

It appears the only two chips on the I2C bus are the CITAC and the 5240 
TTX decoder. The datasheets for both of these are on 
DatasheetArchive.com (though they're a pain in the backside to 
download), which means I already have a pretty good idea what the 
various register bits do.

Problem is, I don't have any data on the tuner module. At all. Heck, I 
don't even know what it is, or what the GPIOs on the CITAC are wired to 
(there are four on Port 1 reserved for bandswitching, plus four 
additional TTL GPIOs on Port 2).

Has anyone here written code to drive the UTA? If so, I could really use 
some hints (example code or annotated I2C traces would be even more 
useful) on how to initialise the tuner and tune to a given channel 
frequency...

I figured if all else fails, I might be able to use the UTA as a signal 
source for my TTX receiver project. This, of course, depends on the 
quality of the video output signal and whether it's good enough to use 
with an external decoder.

Thanks,
-- 
Phil.
philpem at philpem.me.uk
http://www.philpem.me.uk/



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