Updated "ROM-Scanners" and the like.

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

Re: Updated "ROM-Scanners" and the like.

Postby Harry Dalek » Mon Feb 15, 2021 6:37 pm

Steve Anderson wrote:...and to think I threw away literally hundreds of perfectly good (windowed) EPROMs all those years ago...if I had known they'd be still used in the 2020s I would have hung on to them and sent them on to whoever wanted them...same story with tubes/valves/CRTs for most people sadly...

Steve A.

I should do another simple NBTV CRT display in the future, it's been a while since I have...or even a Cop McDonald P7 SSTV display, I have the CRTs. If you have a P7 CRT, wait a while, I'll be back!


Well if you have the room no problem to keep it for a few reasons , i suppose the things we have from the past now around are due to some one hanging onto it .

Yes be good to see you do a monitor with one of your CRTS next i would be interested ,not putting a downer on it we are not around for that long may as well at least know we made some thing with them while we can :wink: .
I am doing this at the moment .

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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sat May 29, 2021 6:17 pm

An Update on this...I'm in the process of designing an updated 'ROMscanner' of Ralphs. But, it's one of the devices suffering from the chip shortage at the moment. I'll be calling it a 'Fotostor'. The storage is a Flash memory of either 16Mb (250 images), 32Mb (500 images), 64Mb (1000 images), and when Microchip get around to producing a 128Mb version, 2000 images.

The image format/specification is exactly the same as the ROMscanner with the option of of using (or not) the unused bit in the data for seven bits of video depth.

At this stage it comprises of four chips not including power supply, a PIC18F14K50 microcontroller (20-pin DIL), the Flash memory already referred to (8-pin SOIC, easily hand-solderable), a serial D-A (8-pin DIL) and either a dual or quad op-amp, (8-pin or 14-pin DIL).

Control initially will be via a PC/USB, but I plan to add a numeric keyboard for image selection making the device stand-alone. Images are loaded from said PC/USB connection. It may be possible to add short sequences of video too, though I don't see that as a priority...

It's early stages at the moment, and I can't make much progress due the long delivery times for chips...

One might say, "Why not use the PC anyway?" the problem as ever is the lack of low-frequency performance, though the 'also-in-development' DC recorder/adaptor for PCs would do the job without being tied to one particular format. It is also designed for moving pictures with audio. So I'll be concentrating on that first. That too is held up by the chip shortage.

Steve A.
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Thu Oct 28, 2021 6:06 pm

Picking up this thread from where I left off...here's my initial go at a circuit diagram...it's a start, maybe it could do with some 'massaging' here and there...though it seems I changed to processor at some point...note, this is a 3.3V system, not 5V...5V seems to be on its way out...

At this time I can only get 32Mb (Mega-Bit) Flash Memory locally, but with some very small changes 64Mb chips will work...

Steve A.

FotoStor Main 1-Model.gif
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sat Nov 13, 2021 2:59 pm

Having dropped the Collatz Conjecture thing, although novel, it's time to resume work on this...

The supply situation r.e. chips is still a bit hit-and-miss, the biggest variable being the availability of the Flash memory. Here I can get up to 32Mb devices, but 64, 128, or 256Mb not until (maybe) well into next year - like June! The rest, at the moment, are OK. Ordering from overseas is tiresome here...so I try to avoid it.

I'll have to make this adaptable for a selection of memory sizes....done, one or two 32Mb/64Mb Microchip devices, larger devices in the future. (128/256Mb).

Steve A.

Postscript: As it's possible to expand this significantly in terms of memory, it's tempting to consider using it for NBTV moving images. However ideally that requires sound also. Rather than go that route there are better ways(?) to do that - which I also started on a while ago. So here's my plan...

1) Complete this 'Fotostor'.
2) Complete the DC-coupled NBTV recorder/playback device...maybe including Chris Long's half-rate NBTV - an option...
3) ...let's get those two out of the way first!!
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sun Nov 14, 2021 3:50 pm

An update on the FotoStor, memory now defined up to 128Mb (2x8MB), larger is possible when available someday...

This will handle still-frame NBTV (as per Ralph Taggart's Romscanner with maybe small changes) plus 120/128-line SSTV monochrome images.

Still considering other modes including the 'Half-Rate NBTV' mentioned above...JP103 may not be required...design ongoing...it may also be possible to reduce the processor to a 20-pin DIL device, though that's probably 'pushing it'...

What is omitted in the attached drawing is filtering will be required on the SSTV output (if used) and on the baseband NBTV/SSTV output. This should only require a dual op-amp and a few passives for each one...

NOTE: The logic supply is 3.3V NOT 5V, the processor and Flash memory are rated to 3.6V Absolute Maximum.

Steve A.

FotoStor Main 1-Model.gif
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sun Nov 14, 2021 4:27 pm

In the future I should perhaps resurrect my attempts at SD-card interfaces, it started out well when the cards were of much lesser capacity than now. Time to catch up with the times Steve! They are simple Flash memory devices though you can look at them as a giant EEPROM from a user point of view, as that is all they really are...though there are traps for the unwary...if you can get through the initialization stage you're 95% there...the first few milliseconds of power-on are crucial...

The 3.3V limit also applies to SD cards...and signal levels on USB, though not power...better get used to it...

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Re: Updated "ROM-Scanners" and the like.

Postby Klaas Robers » Mon Nov 15, 2021 5:51 am

Steve, am I missing picture-select inputs? Because if I can store 16, 32, 64, 128, 256 pictures, I should be able to select them, isn't it?

I just received from Chris acl a small box in which quite some SSTV pictures are stored. He stored them as .wav files on a micro SD-card. The advantage is too that you need no "write" fuction, as you can program the little card (was it 16 GB?) in the slot of a laptop. As far as I understood Chris stored the SSTV as audio files with a playing time of 10 minutes in 8 bits resolution and 8 kHz sample rate. Looks very good!
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Mon Nov 15, 2021 5:10 pm

Klaas Robers wrote:Steve, am I missing picture-select inputs? Because if I can store 16, 32, 64, 128, 256 pictures, I should be able to select them, isn't it?

Very true, and I'm still thinking on that. Initially during development I had in mind to select frames/pictures via the ASCII TTL link, but that's not very practical. Ideally what's required for this is to be self-contained. So I had thought of a telephone-style keypad arrangement as part of the unit, either selecting individual frames/pictures or a group of them, say frame 107 to 134, then loop back. Each frame/picture shown a selectable length of time (NBTV), or number of transmits, say 4, before moving on to the next one (SSTV).

As there is plenty of memory available each 'presentation' listing could be stored based on theme, cars, buildings, nature and so on...

I'm trying to avoid having this tethered to a PC for playback purposes, otherwise why not just use the PC anyway? Except for NBTV the PC output isn't usually DC-coupled, though that's strictly not a requirement, but it does make life easier.

So it's work/thought in progress...though it may just be simpler to add a DC-coupled A-D and D-A interface to the PC via USB, quite easy, and perhaps the more logical/sensible route to go? The problem then becomes one of adding a GUI/user interface to the PC, something I cannot do...though it may be possible to use something that already exists...ideas/suggestions welcome...something like 'jukebox' software perhaps?

Steve A.

I'm reluctant to hand this over wholesale to becoming yet another PC application, but when you consider the other options it (unfortunately) does make sense...at this rate we'll soon forget how to use a soldering iron!

And that outlook I find quite depressing...
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Re: Updated "ROM-Scanners" and the like.

Postby Klaas Robers » Mon Nov 15, 2021 8:00 pm

I agree. The point that I tried to make is the programming / filling of the memory to do directly in the PC. A micro-card or a normal SSD-card can be filled in most computers and then taken out and put into the "ROM-scanner". The little box that Chris ACL made is a nice thing to handle. In fact it is a music player that plays .wav files. There is a push button "Next" and a push button "Previous". The only thing is it has no auto-repeat for endless video.

And of course, MAKING something is much more than running some one else's program in your computer.
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Re: Updated "ROM-Scanners" and the like.

Postby acl » Tue Nov 16, 2021 7:48 am

IMG_3614.JPG


Latest version using genuine DGPlayer mini for both SSTV and NBTV. Open frame construction. Chinese clones do not give good NBTV results. Board includes DC to DC converter, Klaas Robers video buffer amplifier, Audio amplifier and PCB mounted speaker.

Regards Chris Lewis G6ACL
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Tue Nov 16, 2021 1:08 pm

Interesting little device! For NBTV you can forget the MP3 function and just use the WAV mode. Larger files, sure, but none of the compression and crosstalk artifacts associated with MP3...I hope the WAV function is true to specification. Klaas did an item on MP3 compression and crosstalk in the newsletter some years ago...

It appears that a lot of the data for using this device is often wrong, parts missing or simply vague. The attached appears on first glace to be better than most...

This is certainly worth considering, especially as generally so cheap, though I don't suggest going for the cheapest out there...

However, I'm hoping that the 'Normal' EQ setting means 'Flat' or 'None'... I also assume that the LS output is a mono addition of the two channels, though it may be possible to select L/R, I haven't studied the data enough yet. There are separate low-level L/R outputs on pins 4 & 5, DAC_R, DAC_L respectively...whether they are pre- or post-EQ isn't certain.

There is still the question of the output being DC-coupled, if not (probably), where is the LF cut-off point?

Steve A.

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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Tue Nov 16, 2021 5:03 pm

...then there's the slight issue with creating DC-coupled WAV files for NBTV...but AC-coupled versions have worked in the past, so one could say "It's a nice-to-have feature." Though arguably not essential...

As you might guess I'm doing a lot of head-scratching on this, for once perhaps too many choices!

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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Wed Nov 17, 2021 8:30 pm

I must admit, I'm losing my enthusiasm for these WAV/MP3 devices, they may be suitable, though probably not the MP3 versions. Though cheap and easy to use, I'm hesitant.

What I did do some years ago is develop an interface for SD or SD-micro cards which basically involved the two simple modules below. Both now well and truly covered in dust!..

SD Card & USB 1.jpg
SD Card & USB 1.jpg (101.58 KiB) Viewed 315 times


This perhaps could do with a re-visit...

Steve A.
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sun Nov 21, 2021 6:15 pm

Here's the plan...use USB between PC and this device, at first with a simple USB implemented UART/RS232-based terminal-type interface. That could be developed into a GUI by someone familiar with Windows and the like scripting/programming (that's not me, any volunteers?).

The storage would be Flash memory at first then add SD cards as a future extension.

More as this evolves...

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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Tue Dec 07, 2021 8:42 pm

This is evolving as both a NBTV and SSTV device. A bit of simplification has gone on without any compromise. No output D-A for example. simple filtered PWM instead.

The issue I have is generating the input files. but I'm in the process of working on that. Sadly I've had no-one come forward with an offer to make a Win GUI which is beyond me...

Steve A.
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