The 'Hellcat MK I' 625-32 Converter.

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The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Mon Jun 06, 2016 6:23 pm

Somewhere on this forum I'm sure I started a thread on this subject, but even using the features of the advanced search was unable to locate it - that's if it does actually exist. Should anyone trip across it I'll be interested to know of its existence.

Basically standard analogue 625 in, monochrome NBTVA 32-line out.

I've decided to continue with this as the hardware appears compete and it seems I'm someway into the software, so results should be reasonably rapid (says he).

It took a while to locate the hardware in amongst dozens of boxes, but it's seen the light of day for the first time in at least two years as a guess.

To jog memories a snapshot is below.

Steve A.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Harry Dalek » Tue Jun 07, 2016 3:53 pm

Steve Anderson wrote:Somewhere on this forum I'm sure I started a thread on this subject, but even using the features of the advanced search was unable to locate it - that's if it does actually exist. Should anyone trip across it I'll be interested to know of its existence.

Basically standard analogue 625 in, monochrome NBTVA 32-line out.

I've decided to continue with this as the hardware appears compete and it seems I'm someway into the software, so results should be reasonably rapid (says he).

It took a while to locate the hardware in amongst dozens of boxes, but it's seen the light of day for the first time in at least two years as a guess.

To jog memories a snapshot is below.

Steve A.


HI Steve
you mention it here
viewtopic.php?f=1&t=1756&p=15866&hilit=625+line+converter#p15866

and this is i think where you started it
viewtopic.php?f=1&t=1298&hilit=+Video+to+NBTV+converter

There you go a little help back at ya ~ :wink:
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Tue Jun 07, 2016 4:59 pm

Thanks Harry.

I've only quickly skimmed through it, it seems a bit thin on the ground regarding details. Though it does give me an idea of where I had got to. I'm at the stage of refreshing my failing memory and trying to work out what in the heck I was as far as the software goes. Although I like to think I'm quite disciplined when it comes to commenting code, sometimes my own comments defy me!

Thanks again Harry,

Steve A.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Harry Dalek » Tue Jun 07, 2016 7:30 pm

Steve Anderson wrote:Thanks Harry.

I've only quickly skimmed through it, it seems a bit thin on the ground regarding details. Though it does give me an idea of where I had got to. I'm at the stage of refreshing my failing memory and trying to work out what in the heck I was as far as the software goes. Although I like to think I'm quite disciplined when it comes to commenting code, sometimes my own comments defy me!

Thanks again Harry,

Steve A.


No worries Steve ,I think every one here has the inventor in them and there never seems to be enough time for every thing so projects get put aside for the next idea to try and getting back to a past one is always hard.
I think you wanted to keep this one detail wise for the news letter ,i would put it on both less chance of both getting lost in the future .
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Tue Jun 07, 2016 8:08 pm

Yes, I've had a couple of 'prods' from a certain Editor over the past year or so...wondering what's happened...gentle prods I might add. So having mentioned it to said Editor in the past I guess I'd better get on with it!!

I haven't mentioned the NBTV-625 Up Converter yet. Keep quiet guys.

Steve A.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby AncientBrit » Tue Jun 07, 2016 11:10 pm

Steve,

Nice to be appreciated for the quality of your articles.

'So much to do, so little time'

Cheers,

Graham
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Wed Jun 08, 2016 1:30 pm

AncientBrit wrote:...Nice to be appreciated for the quality of your articles....

I think said Editor is just trying to get contributions in rather than being concerned with the quality or otherwise.

So guys, help the poor Editor out...

Steve A.

I'm quite willing to help out in converting a fag-packet sketch into something a bit more presentable if that concerns one. Also to proof-read items too. No excuses now...
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Thu Jul 30, 2020 4:28 pm

Coming back to this after some four years - I'd better get on with it!

Probably the best known 625-NBTV 30-line converter was/is Peter Smith's version, in Newsletter Vol. 25 No. 3 sometime in the year 2000 - though it did do 32 line also.

It's still a valid design, though the fast 6-bit A-Ds are almost impossible to find these days. Very obsolete! (CA3306). Has there been any further articles regarding 625-NBTV conversion? I haven't come across any.

Finding a suitable replacement for the CA3306 isn't easy without opening your wallet wide. This is a hobby, not a research project! But I'll keep plugging away.

I have a number of CA3306 chips here, my plan is to use them first, get the system working with an eye on 8-bit video, and see what alternatives there are to replace the CA3306. There are a number of potential chips (all 8-bit). But until I crunch some numbers it's all open-ended.

**************************

The reason for this is I'm wanting to do the opposite, 32 to 625, but there are few sources of good and stable 32-line NBTV. I guess much like the SSTV-625 up-converter I did some years ago, I had to generate my own source files. The principal it uses is much the same but the data somewhat less per frame so it should be simpler. (He hopes).

Later...Though it would very easy to generate a static NBTV frame source, or even animate it. But I think a 'proper' 625-NBTV device would be useful on its own. A chicken and egg situation.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Harry Dalek » Thu Jul 30, 2020 5:12 pm

Lab guy mentioned to me there's a Philips sync generator chip 625 line out there.... if it helps cutting out a circuit you can program it to 7 tv standards philips-saa1101
https://dtsheet.com/doc/235442/philips-saa1101
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Thu Jul 30, 2020 5:50 pm

Thanks Harry, and Lab Guy too. I've seen that chip in the past some years ago, but it is what it is, just a SPG. The PIC I used in the previous SSTV-625 up-converter did all that plus read from the memory and outputted the data ready for a 625 D-A. As this is monochrome there's no requirement for a colour sub-carrier for composite, nor YUV or Y, Cr, Cb for component video. Though I have to confess I haven't done a 525/60Hz version...though most modern TVs will almost accept anything analogue. Mine even accepts SECAM! Egads!!

I wonder if it's still available? It is quite an older generation device, probably a 1980s chip. But thanks for the suggestion, it could well be useful to others...

Steve A.

Though I must admit SECAM on 525 would be interesting! Maybe not.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Fri Jul 31, 2020 4:58 pm

Somewhere, some time back I did knock up an equivalent device for this using a PIC micro for 625/50 but only for monochrome. No 7.8kHz output for PAL sub-carrier phase switching for example. I think I squeezed it into a 14-pin device...I'll have a dig around...it wouldn't be hard to re-do if I can't find the old version. Either would be fine for monochrome or component video (YUV or Y, Pb, Pr).

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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Sang15512 » Tue Aug 25, 2020 4:57 pm

Nice info great work
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Mon Nov 02, 2020 4:55 pm

Well, where does time go? Four years since the last relevant post! I am now actively following up on this. At first I'm going to have a go at 525/60 to 15Hz and 7.5Hz NBTV (at the usual 48x32 pixel arrangement). Then apply the lessons learnt for 625/50 to 12.5Hz and 6.25Hz...that is when I can get a suitable 625 TV camera. Hence my recent posting in the 'Marketplace' section for a source of 625 TV camera modules. In the interim I may be able to use the fibre set-top box which in addition to the HDMI interface has YUV outputs, I'm hoping at 625/50. Otherwise I have no other source of 625/50...which raises the question, "Is this sort of thing required anymore?"

However, in those intervening four years things have moved on and the version I'm planning should be simpler than what I was considering all that time ago.

The only other FSTV to NBTV converter I'm aware of is Peter Smith's (G4JNU) design featured in CQTV 189 of the year 2000. It may have appeared in the NBTVA newsletter too, but I'm not sure when or if.

Have there been any other versions since, or even before? It uses our old friend the obsolete CA3306 six-bit A-D...and those are getting hard (and expensive) to find these days. Though there is a supplier here in Bangkok who has over 60 in stock for around US$3.50 inc. VAT. I guess after they've gone, no more...

Steve A.

As it's a free and open download from the BATC website, I've attached issue 189 of CQTV here, Peters item starts on page 15.
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Harry Dalek » Tue Nov 03, 2020 8:02 pm

Hi Steve lab guys doing a nbtv signal generator might be interested on he's take on this was not talking about Andrew in Tasmania ? New Zealand ?

youtu.be/pP5OypBivys
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Re: The 'Hellcat MK I' 625-32 Converter.

Postby Steve Anderson » Tue Nov 03, 2020 8:33 pm

Yes Harry, "Labguy" in the US does have many interesting videos and subject threads on his site. I may get in contact with him in due course...

For the moment here's my initial go at the guts of the updated "Hellcat" convertor, there's more to be added but it's quite simple peripheral stuff.

There's still a few unknowns (as usual), but they'll iron themselves out down the road, I'm not too concerned. The items in red are mostly notes to myself...ignore them...

Note, this will not do cross-conversion, i.e if the input is 525/60 you have a choice of 15 or 7.5Hz output. Likewise 625/50 will only yield 12.5 or 6.25Hz output.

I know someone will ask, "Why are you using a 12-bit D-A?" Simple, I have some kicking around, they're more than fast enough. they're cheap and they do the job. Possible alternatives are a DAC-08 (needs more pins on the micro and needs +/- supply volts) or an R2R ladder (same hassle). The MCP4821 is only eight pins, less board space...the alternative is to use one of the PWM outputs of the micro and then filter it, possible...hence CCP4 & 5 outputs noted in red...you still need the gubbins for the filter(s) though...

Some may wonder about the 6.25/7.5Hz output selection. I was impressed by Chis Long's linked-to video in the recent NBTVA newsletter that I thought it would be foolish to leave that option out. You don't have to use it if you prefer not.

I know this can all be done in software, from start to finish, and although there's a modicum of number-crunching here, to me it's still a hardware build.

The day I don't need to plug in my soldering iron will be a sad day...
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