NBTV/SSTV-625 Up Converter MkIV

[Harry Dalek]

Bit more work today i hope i am getting right i changed some part positions and started on connecting up the power rails to the ics and decoupling capacitors .

I am getting close to looking into the wiring below, I understand most of the wiring Steve and Chris but the 2 screen grabs below i am head scratching i pretty much have no idea to me all that wiring looks shorted together which i doubt ,is it some short hand for this bundle of connections ? but i need some explanation reassurance what's happening before i attempt getting hold of the soldering iron on this area.

Screen 00003.jpg (58.82 KiB) Viewed 7343 times

Screen 00002.jpg (38.7 KiB) Viewed 7343 times

[acl]

Harry,

There are 10 interconections connections between the two RAM chips, the two (at present) PICs and the D to A converter.Apart from SLK and CS(both underscore) D0 to D7 you need to hook up between chips( eight seperate connections) All you need to do is connect all the D0's together and carry on up to D7. The remaining two connections SLK and CS(both underscore) only go between the two PICs and the RAM chips. Andrews notation is a standard method of simplifying schematic diagrams.

Hope this helps.

Chris

[Harry Dalek]

Harry,

There are 10 interconections connections between the two RAM chips, the two (at present) PICs and the D to A converter.Apart from SLK and CS(both underscore) D0 to D7 you need to hook up between chips( eight seperate connections) All you need to do is connect all the D0's together and carry on up to D7. The remaining two connections SLK and CS(both underscore) only go between the two PICs and the RAM chips. Andrews notation is a standard method of simplifying schematic diagrams.

Hope this helps.

Chris

I must admit i have never heard of the Andrews Notation ! i can't see i have really noticed this type of short hand wiring before either .. i will have to put my big boy pants on and learn !

Having never touched any thing like these chips before i am totally unfamiliar with their wiring ...but the D/A chip i am ! ok with that one that's where i was seeing the problem .

23Lc1024 ics ic 201 202 ..D0 to D7 connections to the D/A chip D0 to D7 connections that makes sense i get that ,that wiring is corrected in my head .

So the DO to D7 on both 101 and 102 IC's are also connected in parallel to each others D0 D7 connections and also to the above D/A chip D0 to D7..?

The IC201 Rams SCK connection to 202's SCK ? and CLS both connected together and those again parallel to the ic101 102 sck and cls connections ?

Just call me junior ! i just want to wire it correctly .

Thanks Chris for the help here

[acl]

Harry,

That right. Just connect the signal like to like and you will be OK. This is why there are so many green wires under my board. If you look at Steves MK1 these interconnection cable are routed on the component side.Perhaps I should have done the same. Anyway, I have plenty of time as the UK is in a complete lockdown and the dog can only take so many walks.It always a comprimise between functionality and neatness. If Steve can get it down to one processor and we can get a nice PCB produced then our results will be consistant. Remember Edison said ' I havn't failed but I have learnt 1000 ways in which not to make a light bulb'. and remember it is not a failure but a defered success.

[Steve Anderson]

I think you've all got the gist of this 'buss shorthand' now, it's been part of my work for over three decades, I'm sorry if it's confused some of you, but it really is very common now. Just follow wherever D0 goes to, then D1 and so on. What may also be confusing is the 'D0-D3' and D4-D7' connections on the RAM chips are both inputs AND outputs, i.e. bidirectional. Data goes into, and later comes out of the same pins....as well as the instructions for the action the RAM needs to take as well as the address as to where this happens.

E.g. to store a byte...send the instruction to store a byte, send address as to where to store the data, then send that data.

To retrieve that byte later...send the instruction to retrieve a byte, send address where the byte you want is stored, then 'suck the byte out'....so to speak.

All the time keeping track of where everything is stored in RAM. All RAM (memory in general) work in much the same way. Much the same as an index in a public library, "I want this book, where is it located? Go get it," opposite process to put it back or replace it with a new edition (same address, new book). All you need to do is keep track of where the heck it is and what it is.

Right now I'm working on that 'overshooting filter' I mentioned a day or two back. This requires only a small amount (134 bytes) of memory but requires 'shuffling down' a software conveyor belt, then doing 67 16-bit x16-bit signed multiply routines yielding 67 32-bit resultants. adding those resultants, then coming up with the final result. All to stop that damn overshoot or 'ringing'.

All the while whilst doing A-D conversions and keeping the RAM updated and not trying to access RAM while the read micro needs to output it to your screen...all very time and code sensitive...

Steve A.

[Harry Dalek]

Harry,

That right. Just connect the signal like to like and you will be OK.

OK Chris i think i have got it now thanks for the help again ...for me its like a valve guy looking at a IC for the first time wondering how the hell does this thing work !

Now i know how the wiring go's i can move forward .

This is why there are so many green wires under my board. If you look at Steves MK1 these interconnection cable are routed on the component side.Perhaps I should have done the same.

I tend to do it from the top like Steve if i have to use a lot of insulated wire wiring ,i try to wire like you see under my board if there are neat ways to do this to keep the top wiring low but i can see in this case i will need to do an amount of insulated wiring ,in some ways its easier but worrying each wire is like a little transmitter to its fellow wire next to it at these frequencies .

I only see a positive that 3 of us are not 100% copies as it will show if one of our construction method's will show any problems or not .

Anyway, I have plenty of time as the UK is in a complete lockdown and the dog can only take so many walks.

People are funny things you have the Type that will listen and the other type rebellious ! In Australia we listened to the advice and just did it and only people with the virus are people returning from over seas other wise no one has it here any more ... We have the complainers as well i don't want to wear a mask i don't want to stay home so on we just fined the hell out of the them or worse if there still didn't listen ....you can see in the USA freedom do as you like gets you nowhere . i had 2 months last year at home could not work or see any one from another house hold or other family or go 15km from home food shopping only... every where a mask on and it worked .

It always a comprimise between functionality and neatness.

Back to the Project Yes and you sort of have to use what you have at hand or it gets expensive .

If Steve can get it down to one processor and we can get a nice PCB produced then our results will be consistant. Remember Edison said ' I havn't failed but I have learnt 1000 ways in which not to make a light bulb'. and remember it is not a failure but a defered success.

[/quote]

I solder the other socket in just in case may as well be there .

Yes always learn from failure ,i rather like this form of wiring we are doing it will be more satisfying when you flick the on switch and it works ,The PCB i understand for a big run other wise it could be expensive and in time ...for me i am learning more this way have to think more .

Its OK Steve just some thing i have to learn if that's the way wiring shown these days ...i will just ask it i am not sure so far i am ok with every thing else .

[Steve Anderson]

A single-processor version is not going to happen in the short-term. I'll have to get to grips with 16-bit PICs first (PIC24s), that could be a steep and slow learning curve. So we'll plod on with this version for now, the single processer version wouldn't provide any better results, just one less 24-pin package which isn't much in the overall scheme of things.

Still working on 'that' filter, the Excel chart FIR waveform is better than the analogue version. Next I'll build up a stand-alone prototype to do an A-B comparison, before trying to shoehorn the code into the write processor. The write processor is doing 80% plus of the work, the read processor has an easy life in comparison.

Rising edge of video shown, values on the Y-axis need to be scaled and offset yet. The bulk of the risetime is 3/8000s of a second (sample rate is 8kHz), or 375us, that time and particularly the under/overshoot duration are much shorter than previous. All done in code, not a capacitor, resistor or inductor in sight! The negative-going version is an exact inversion.

Steve A.

[acl]

Hi Steve , it looks like you have been busy. When you have some initial HEX files I could try out on my board. I know we are not expecting perfection because of my layout but at least we can give it a go. Keep up the good work Harry.


Regards Chris

[Steve Anderson]

...it looks like you have been busy...

...slightly! This version is a lot heavier on the software component than the MkI which was a "Brute force and Ignorance" device. I'm hoping this will have some finesse to it. Me? Finesse? Get outta here!

When you have some initial HEX files I could try out on my board. Regards Chris

Probably the read software will be the first to appear as this is primarily a 'port' of the MkI version with the exception of the RAM which uses a SQI (Serial Quad Interface) bidirectional port for all communication to/from it rather than some 27+ pins for conventional parallel access. No wonder nobody asked for the code for the MkI !!

Now, we're going to need some test material, (SSTV .wav files etc.) for this. There are my files I uploaded on this forum some years ago, they'll get you up and going but they're not what I would call 'Test Cards'. Your thoughts gents?

I did recently mention the converse to this device, taking a still photo and converting it into the required .wav SSTV format. As your old lecturer would have said, "Discuss". This is an ideal app for a PC. As much as I don't want to admit it writing that code is beyond me, but it could be done in Qbasic..what?? Dinosaur! If anyone wants to put their hand up, please go ahead! I'm sure there are already on-line versions that can do it, but how well? I know of one, but it generates 4:3 images (160x120) rather than the original 1:1 square format. Here, the preference would be 128x128 not including sync encoding, both is US and EU line/frame rates. Contact me. or a quick post here, if you need the timing standards...yes, I'm ever hopeful...

Should anyone thrust their hand up I'll start a new thread for SSTV file generation.

But if there's no response it can be done in hardware the old fashioned way...

Steve A.

[Harry Dalek]

Now, we're going to need some test material, (SSTV .wav files etc.) for this. There are my files I uploaded on this forum some years ago, they'll get you up and going but they're not what I would call 'Test Cards'. Your thoughts gents?

Yes i would think for testing very much so for you more than us as its your baby here a Test card for 120 line card showing frequency response bandwidth as old tv station test cards did for 625 line ..just to see how what go's in comes out looking the same .
I am sure Chris thinks the same this device does not have to be perfect but it very well may be !
I recall you did a reversing wav for SSTV or grey Bar wav ...i will look for that also .
Would a WAV with the VIS code effect it ? as you could knock current software .
But your your uploads would be a fine test to start with ok with me .

[acl]

Yes, I am happy with that. I think there is sufficient SSTV material at the moment to get our convertors working. It would then be nice to move on and produce a stand alone unit to produce SSTV images. I use the video below to check operation of my SSTV equipment.

https://www.youtube.com/watch?v=u3k6Xt30Z7g

Regards Chris

[Steve Anderson]

Would a WAV with the VIS code effect it ? as you could knock current software.

I've seen a few mentions of a VIS code for 7.2/8.0s 120/128-line monochrome SSTV, I'm not sure what effect they would have on this device if they were present. I'll do some investigation.

If I'm correct the 30ms frame pulse is missing, though the 5ms line pulses are present. The VIS code effectively taking the place of the 30ms frame pulse, but I think it occupies a complete line. If that is the case then this device will not work with VIS-encoded signals. Perhaps something to look into for the future. If at all possible it would be a software change only. More work for the write processor...

As I say, investigation required...but for the moment it is for the future...

Steve A.

Done a bit of research, the VIS code will completely screw things up in terms of frame timing, maybe, and maybe once the VIS code has passed the line sync works, but that still makes the whole thing useless if it can't be properly framed. I'm gonna pause and contemplate how to proceed.

I wonder how much 7.2/8s SSTV with VIS code is around?....if any? In addition the VIS code uses a tone below the usual 1200Hz, that is 1100Hz, it's no big deal but it needs consideration. Also the entire VIS code takes 910ms (0.910 seconds), around 15 lines!

Calibration header with VIS code
TIME(ms) FREQUENCY(hz) IDENTITY
300 1900 Leader tone
10 1200 break
300 1900 Leader tone
30 1200 VIS start bit
30 bit 0 1100hz = “1”, 1300hz = “0”
30 bit 1 “”
30 bit 2 “”
30 bit 3 “”
30 bit 4 “”
30 bit 5 “”
30 bit 6 “”
30 PARITY Even=1300hz, Odd=1100hz
30 1200 VIS stop bit
Note that all mode specifications begin immediately after the VIS stop bit.

Steve A.

[Klaas Robers]

A test picture? What do you think of this one?

Testbeeld512.GIF (16.58 KiB) Viewed 7262 times

It is 512 x 512 pixels, in square format. The first line is black, it is there to place the V-sync.
Somewhere in this forum you will find the .wav file. Use it, that's why I designed it.

[acl]

Very good Klaas,

How did you generate this picture?


Regards Chris Lewis

[Harry Dalek]

Done a bit of research, the VIS code will completely screw things up in terms of frame timing, maybe, and maybe once the VIS code has passed the line sync works, but that still makes the whole thing useless if it can't be properly framed. I'm gonna pause and contemplate how to proceed.

I wonder how much 7.2/8s SSTV with VIS code is around?....if any? In addition the VIS code uses a tone below the usual 1200Hz, that is 1100Hz, it's no big deal but it needs consideration. Also the entire VIS code takes 910ms (0.910 seconds), around 15 lines!
Steve A.

Arrrr So software that can make a 8 sec with a VIS code will cause problems mmm,an idea could be to edit the VIS code out with a sound editor ?
Am i right in saying The standard 7 and 8 sec SSTV started with a frame pulse so this could still be a problem unless you manually reset which more than likely you have built in here .
Below some more SSTV from Klaas we could also use
viewtopic.php?f=24&t=1926&p=17638&hilit=mmsstv#p1763

I have been working more on the project today finished the out put part of the DAC ..