Hedghog PSC programmable standards converter
This is my latest standards converter. It is programmable so can generate a range of standards from a 625 line input. It also comes with a programmable modulator.
The converter can generate a standard with any number of lines from 16 to 830 and any number of active lines(lines with picture content) between 8 and 800.
It can generate field rates of 25, 30, 50 and 60 Hz. 50 and 60 Hz are interlaced. It has selectable sync height from 20 to 50% in 5% steps. The length of the front porch, horizontal sync pulse, back porch and broad pulse are all programmable. The number of broad pulses can be in the range of 1 to 50. The left and right of the picture can be cropped independently. There is also a method of moving the picture vertically.
The modulator uses two MC44BS373. It covers 30 to 900 MHz in 5 ranges. The frequency step size is dependant on range.
It can do negative video and FM sound or positive video and AM sound.
It can do video/ audio carrier separations of 4.5, 5.5, 6.0 and 6.5 MHz or if in positive video and AM sound mode the video and sound carriers can be set independently.
Both the converter and modulator can be easily programmed by using the two control knobs.
Some basic knowledge of the standard you want to generate is needed.
I have tested it myself and can confirm it is not idiot proof. It is possible to enter nonsensical settings in such a case it will just sit there not producing any output.
I have tested it on 405, 819, 625 and 525 lines. That's as far as my collection of TV's goes. Anything outside those have not been tested but should work.
A link to a description of the menu is here.
The first 3 photos below are of 405 lines. They are of the same test card but by changing the active lines, crop and vertical shift it can be displayed in different ways.
The next photo is the Sony TV displaying a 819 line picture.
The photo of the monitor displaying test card F is a 647 line picture. This is just to make the point it can generate any number of lines not just set standards. I expect running the monitor at 647 lines wasn't great or it but I didn't leave it running long.
Absolutely outstanding work Frank, you are to be commended for all the efforts you have put in to designing all the versions of the HedgHog. 👍
Now offering a Multi-standard version has plugged a gap, as the Aurora had long ceased to offer multi-standard and, It's always great to have another choice. Your standards convertors might have come along at a very good time as who knows how much longer the Aurora will be produced. Should it ever stop, the vintage TV community still have a way to use their TV's.
Big thumbs up to Stephen @freya for building these for folk who either do not wish to or cannot do it themselves. Hmmm I might have to take the plunge soon.
Thanks for putting the link to Stephen in my post, I had forgot I could do that.
No problem Frank, you're not alone, many forget as it's only a feature available on newer forum software such as we use here. 👍
Very nice! I might have to have a go at building one, I have that American Motorola TV that runs on 525 lines that I could use it with, at the moment I just run it on 625 via a cheap modulator!
I was using one of the 2 Hedghog’s I built yesterday on my Murphy V180C, picture is excellent, a very useful little box of tricks! It’s one of the early ones with the plug-in FPGA board too.
When on 30 or 60 Hz field, moving content can have a little jitter. This is because the conversion from 50 Hz to 30/60 Hz is done in a simple way. But it is none worse than you can find sometimes on some satellite channels.
Yes, all credit to Frank for giving us the 'Hedghog' family! I've had an Aurora for years and it's great, but it's a bit, well boring! It's just a black box that you stick 625 into a get 405 out- where's the fun in that? It's a very good bit of kit and has been the saviour of our hobby for many years and has a well earned reputation. Rightly so, but...
I was inspired to build two MK1 Hedghogs, partly because of all the user controls which make it more versatile, but mainly because my first reaction was 'It's mental- I can't build something with insanely small bits with no legs that I can't even see! Plus I'm a computer Muppet and would have to program up the FPGA myself.
I did initially reject the whole idea as too steep a learning curve, but then felt guilty that I really should have a go and make the effort.
The programming caused me more problems than the construction, especially as I was using a Linux PC and I really have no idea how to do things at the command line in Linux! However, after a very long thread on UKVRR&R and much help from Frank and others, I succeeded!! I felt dead chuffed!
Whether I would tackle a MK2 which involves soldering in the FPGA directly to the board is another matter, but I suppose I would have to give it a go.
All in all a very rewarding project which I thoroughly enjoyed and I would recommend giving it a go!
Anyone that has built a Hedghog should have no problem building any of the others.
Soldering the FPGA may look daunting but it is really no more difficult that the TVP5150 decoder. In fact I find it a little easier just because if its size makes it a little easier to handle. Soldering the components to the PCB is not one of my stronger points. It does take me a while to get one populated.
Very impressive Frank.
How long did it take you to learn Very Hard Descriptor Language?
@irob2345 Thank you.
I started to learn VHDL when I was building the first Hedghog. I was lucky as I got some great lessons from Jeffrey Borinsky on the Golborne forum. I had done some microcontroller programming before I started VHDL. At the start the hardest part was trying to keep microcontroller programming out of my thinking. Because the way you have to think when programming an FPGA is totally different to programming a microcontroller. Learning was a case of just getting at it and making loads of mistakes, and I am still learning.
VHDL has plenty of quirks and at first I couldn't understand why they did certain things in particular ways but as I got to know the language it made perfect sense. I really like the language now, It is one of my favourites.
C was a language that I had not learned but always wanted to have a go at. I felt I was missing out not knowing even just a little about it. So last year when lockdown started I did an online course on it. I thought that I might use it for programming the microcontroller for this project. I gave it a try for a while but then abandoned the idea. Because to me C felt like a language that had been shoehorned into the role of microcontroller programming. It has neither the preciseness of assembler nor the convenience of a higher language. I know the C is used in professional circles but if you don't have to conform to that, in my opinion there are better languages for programming microcontrollers. My choice is Great cow basic with a dash of assembler thrown in when required. I know of JAL but there is probably more.
I have updated the firmware on the Hedghog PSC webpage.
The FPGA and PIC firmware has changed and also the menu description has been updated to take account of the changes.
The update adds some new features.
It can now convert from 525 lines as well as 625 lines. The input standard is automatically detected.
I have also added some test patterns. Test card, Grey scale, Cross hatch, cruciform, Black screen and White screen.
The test patterns are inserted before the converter so are available on all output standards.