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PIC 405 line pattern generator

 
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Re: PIC 405 line pattern generator

Post by Briancuff » Sun Jan 03, 2016 7:04 pm

What a feat, Frank. It seems the "ask and you will be given" is true with your PIC programming. I tried to start once and bought a load of kits from Farnell to teach myself! However, I couldn't find a book which started early enough back in the basics so I gave up. I didn't even get an LED to light!

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Sun Jan 03, 2016 10:03 pm

Hi Brian
PIC's can make light work of some tasks.
If you give PIC programing a go again can I suggest trying Great Cow Graphical Basic as it was from there I started from. It is graphical biased using flow charts, you literally drag and drop the elements of the flow chart into the position you need them in and then just fill in the blanks. It made starting off easy.
I have seen two or three books on PIC programing and the all started off with assembler which can be difficult to use at first. Wheres I would think is it better to start with something like basic, get a bit of confidence using it and then move on to assembler.

Frank

 
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Re: PIC 405 line pattern generator

Post by Briancuff » Sun Jan 03, 2016 10:08 pm

Thanks for the advice, Frank. I may well give it a go - old dogs and new tricks spring to mind though!!

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Mon Jan 04, 2016 9:48 pm

A separate V sync output has been added, I will add a H sync output as well. It is easy to see the Frame broad pulses now, photo below. Separate outputs for odd and even field H sync can be added easily, but I cant think of any need for them . I added those outputs temporary and took photos of the odd and even frame syncs.

Frank
Attachments
testcard16 brosd pulses .jpg
odd and even frame sync
testcard17 odd field .jpg
odd frame sync
testcard18 even field .jpg
even frame sync

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Tue Jan 05, 2016 12:34 am

Just to add to the last post. The positive going edge of the V sync output occurs just after negative going edge of the first broad pulse. The negative going edge occurs towards the end of Field blanking period. The V sync output pulse varies by half a line length depending on whether it is in a odd field or even field so the negative going edge syncs up with the lines following the field blanking. This allows the V sync output pulse to be used to sync to the broad pulses (positive going edge) or to the lines (negative going edge).

Frank
Attachments
testcard19 end of field sync .jpg
Lines following the frame blanking period synced with negative going edge of V sync output pulse

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Tue Jan 05, 2016 12:39 am

:aad

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Sun Jan 10, 2016 9:20 pm

Progress has slowed down as work is getting in the way, even so I have added three more screens.
They are Bounce, Crosshatch and Missing line sync.

Bounce as described by Cathovisor toggles the video output between black level and peak white, it remains in either state for 25 fields.

Crosshatch I think is self explanatory photo below.

Missing line sync is a screen of vertical lines.
Quarter way down there is one line with no sync. Half way down the screen there are two lines in succession with no sync. Three quarter way down the screen there are three lines in succession with no sync. Each line that has no sync is marked with a dash at its center.

Two photos below of Missing line sync one of a Sony 9-90UB the other is a TV22. They react differently I presume the Sony has flywheel sync?

Frank
Attachments
testcard20 crosshatch.jpg
Crosshatch
testcard21 missing line sync sony.jpg
Sony
testcard22 missing line sync TV22.jpg
TV22

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Sun Jan 10, 2016 9:32 pm

FRANK.C wrote:Two photos below of Missing line sync one of a Sony 9-90UB the other is a TV22. They react differently I presume the Sony has flywheel sync?

Certainly does Frank - whilst as you know, the TV22 is direct sync. That's an interesting test, that!

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Mon Jan 11, 2016 8:38 pm

I have added another screen, it is similar to the last one. This time all the line syncs are there but three arrive early by different amounts . This is achieved by making the front porch shorter and increasing the back porch by the same amount.

From top to bottom the sync pulse arrives early by 0.33 uS, 0.66 uS and 1uS. Each line that the sync pulse arrives early is marked with two dashes.

The two photos below are again from The Sony 9-90UB and the TV22.
It interesting to note that while the Sony takes several lines to regain correct lock after the early sync the TV22 locks immediately.

Frank
Attachments
testcard23 early line sync sony.jpg
Sony
testcard24 early line sync TV22.jpg
TV22

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Mon Jan 11, 2016 8:45 pm

Thus demonstrating the difference between flywheel and direct sync.

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Fri Jan 29, 2016 10:08 pm

Another Crosshatch Screen has been added, it is the same as the first except it is white on grey wears the first was white on black which can be harsh on some timebases.

I have changed to a 18F2685 microcontroller which is able to hold the two test cards plus the other 10 test patterns.

The bottom greyscale from the test cards has been removed (pictured below).
There is just some small issues to be sorted with the software now.

Frank
Attachments
testcard25 .jpg
testcard26 .jpg

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Thu Feb 04, 2016 11:12 pm

Below is the circuit diagram of the Pattern Generator.
Pins 22,23,24 and 25 of the PIC generate the video information.
Pin 18 produces the sync. D1 and C6 help to shape the sync pulses.
With the values shown the output into 75R is quite close to 0.3V Blanking, 1V Peak white.
If the Video needed to be set precisely, R4 and R5 could be reduced in value and suitable trimmers inserted in series with each of them.
R4 sets the sync height and R5 sets peak white.
Two push buttons are used to scroll up/down through the test patterns.

The stripboard turned into a right rats nest so I made a new one.

Frank
Attachments
pat-gen 040216.png
testcard27 .jpg

 
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Re: PIC 405 line pattern generator

Post by Katie Bush » Fri Feb 05, 2016 12:05 am

That's a very neat piece of work, Frank, and way out of my league, but it has been interesting to follow this thread.

I was wondering if you were aiming at a building your own modulator to go with it, and if so, would there be audio included? Perhaps with tone generator and/or audio input? That would make a nice "testcard and music" option, plus, you've got "music while you work" :)

Marion

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Fri Feb 05, 2016 12:36 am

Thanks Marion,

Eventually I will build it on a PCB and mount it in an Enclosure. I have purchased a modulator kit from ETF and intend to pair it up with that. It has has an audio modulator as well so test card music is a definite possibility.

Frank

 
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Re: PIC 405 line pattern generator

Post by Wolfie » Fri Feb 05, 2016 8:39 am

It shows the progress from hardware to software as a means of getting things done in the real world..

I had my doubts at the beginning but could see where you were coming from and the hardware turned out so simple in the end, gonna miss this thread, so where do you go next? (how about full colour test card F? :qq1 )

Well done that man!

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Fri Feb 05, 2016 9:09 pm

Hi Wolfie
Thanks for the comments.
I guess microcontrollers are just a progression of TTL etc. The thread isn't quite finished yet, still got to complete the software and box it up.

Frank

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Wed Feb 10, 2016 9:15 pm

Added another test pattern "Cruciform"
According to this web site this pattern was often transmitted before programs started up until the sixties.

Frank
Attachments
testcard27 cruciform .jpg

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Wed Feb 10, 2016 9:29 pm

Otherwise known as "Art Bars" :) IIRC the Mark 2 Dinosaur converters would put that out in the absence of a valid input signal.

Frank, are you planning to sell pre-programmed PICs in the future? This is a fabulous device and really deserves a wider audience.

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Wed Feb 10, 2016 11:44 pm

Cathovisor wrote: IIRC the Mark 2 Dinosaur converters would put that out in the absence of a valid input signal.

Hi Cathovisor
That's interesting I hadn't known that.

Cathovisor wrote: are you planning to sell pre-programmed PICs in the future?


Unfortunately simply due to not having the time that's something I wont be offering.
However when I have the software finished (which will take sometime yet) I will be offering it free to anyone that wants it, possibly by attaching it to this thread. A PICkit 3 or similar would be needed to program the PIC, I suspect at least some members here has one.

Frank

 
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Re: PIC 405 line pattern generator

Post by Refugee » Thu Feb 11, 2016 10:20 am

Could it be posted as an ASM file?
I have got kit that can make it work with a range of chips from an ASM file.

 
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Re: PIC 405 line pattern generator

Post by Briancuff » Thu Feb 11, 2016 12:27 pm

Cathovisor wrote:Otherwise known as "Art Bars" :)

In my early days in broadcast TV (1959+), this signal was know as "Pulse Cross" or something similar. It was used as a general signal but also used, together with delays switched into monitor scan circuits, it enabled critical viewing of the field sync area of the picture. This, of course, was very important for correct VTR set-up!

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Thu Feb 11, 2016 2:16 pm

I would say that if you said "pulse cross" to me, the delayed picture on a monitor is what would come to mind. As you said, essential with VTRs.

 
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Re: PIC 405 line pattern generator

Post by Briancuff » Thu Feb 11, 2016 4:37 pm

You're right (again) Cathy. I was getting mixed up with the terms. In fact the term we used was just "bars" (I never heard them referred to as "Academy bars"), These were used a lot as a general purpose test signal (hence my confusion with pulse cross). The line-up signal, of course, was sawtooth. - "Sawtooth and tone on OS1".

 
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Re: PIC 405 line pattern generator

Post by Cathovisor » Thu Feb 11, 2016 5:33 pm

Brianc wrote:The line-up signal, of course, was sawtooth. - "Sawtooth and tone on OS1".

Now that's interesting because I often wondered what the routine line-up signal was in the monochrome era - and now I know :) Thanks for that. Was it a linear or gamma-corrected sawtooth?

I sort of expected something like pulse and bar, but was that normally only reserved for circuit testing?

 
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Re: PIC 405 line pattern generator

Post by FRANK.C » Thu Feb 11, 2016 8:02 pm

Hi Refugee
I will post it as a hex file ready to be uploaded to the PIC. There isn't much choice in PIC's for this project due to the resources it requires. I am using a 18F2685 the only other possible contender in a DIL package is it's bigger brother the 18F4685 which is a 40 pin device. Anything else that might work is in a SMD package haveing 64 or more pins.

Brian and Cathovisor
I find it really fascinating that such a simple pattern was used so much I had assumed that more elaborate patterns would have been the norm.

Frank

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