NBTV on the Raspberry PI

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NBTV on the Raspberry PI

Postby acl » Tue Dec 07, 2021 4:06 am

IMG_3622.JPG



I'm trying to make Gary Millard's excellent programs work on the Raspberry PI. At the moment I have managed to install Windows 10 on a PI 4 and am able to run the big picture. See screen shot attached. I have now followed on by loading the Linux Twister 0S onto the PI 4 and tried unsuccessfully to run these programs in 'wine'. If anybody has any ideas these would be most welcome. My intention eventually is to run Gary's programs on a standalone Pi zero 2 with a 3.5 Inch touch screen.


Regards Chris G6ACL
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Re: NBTV on the Raspberry PI

Postby Harry Dalek » Sun Dec 12, 2021 1:54 pm

This sounds very interesting ,i have never really looked into all this as i tend to like to do the hobby in a simplest way so tend to stay away from this side of it ,but please do show results as i know this could be very useful to others .
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Wed Jul 20, 2022 10:09 am

Interesting I am working on software for Ubuntu Linux and have been getting something that looks like a picture, as I have been involved with ATV, I have been reusing the same type of video circuits. This board is built around a simple dual ADC interface for the Linux viewer, but it is a good place to start with for NBTV. Therefore I will go through this site looking at what has been done before and get some new old ideas, so far I am working it out as I go and have made a lot progress on this project.
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Re: NBTV on the Raspberry PI

Postby acl » Mon Jul 25, 2022 5:50 pm

Hi there,

Sounds very interesting. Please keep us updated with your progress.

Regards Chris Lewis G6ACL
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Wed Jul 27, 2022 8:46 am

Hi Chris,

It all comes down to what time I got to work on this project, I am still looking around for a NBTV scan-converter, something like the Aurora world converter wc-01, but it is no longer been made. So the viewer is my starting point, using the RCA 60 line system at the 12.5 frames per second, as I have seen good pictures with this format looking around on YouTube.

The parts I am experimenting with are the:
TCL5540 ADC
UM245R USB interface
MAX295 Switching filter

And a FPGA with a few other IC's to give me a DC to 50kHz video inputs for the Y / C signals with V / H sync logic inputs.

Grant
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Re: NBTV on the Raspberry PI

Postby Steve Anderson » Wed Jul 27, 2022 6:20 pm

Grant, thanks for the mention of the MAX291-296 chips, until ten minutes ago I was totally unaware of these devices - yet they've been around since the late 90s. They may be overkill for the use I had in mind for them, a post-demodulation filter for SSTV instead of using the usual dual op-amp and a bunch of passives arrangement.

If (a big if) I can get them here I may give them a try...though cost may also be a deciding factor...just checked, they range from 5 to 13 GBP in small quantities (Element 14, UK) - so maybe one day on a future design. The SSTV demodulator I'm currently working on is already hardware designed, 'just' the software to do now.

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NBTV on the Raspberry PI

Postby acl » Thu Jul 28, 2022 5:50 am

Hi Grant,

I'm slightly confused here you will have to excuse me. Is this a stand alone project using Linux or is it incorporated as an interface to the Raspberry PI?

Regards Chris Lewis
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Thu Jul 28, 2022 5:59 am

Hi Chris,

The application should work on any type of Linux, such as Raspbian OS as on the Pi, as long as there is a USB port to connect the interface to.

Grant
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Thu Jul 28, 2022 6:11 am

Hi Steve,

"thanks for the mention of the MAX291-296 chips, until ten minutes ago I was totally unaware of these devices" I have been using them for almost 10 years now on wide range of AF and RF projects. In this application it lets me set the video bandwidth before the ADC, by changing the clock frequency at a ratio of 50:1, say if you wanted to change to a different video mode for example.

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Re: NBTV on the Raspberry PI

Postby Steve Anderson » Thu Jul 28, 2022 12:09 pm

GrantXTV wrote:In this application it lets me set the video bandwidth before the ADC, by changing the clock frequency at a ratio of 50:1, say if you wanted to change to a different video mode for example. Grant

Yes, they seem to be the answer where you want variable cut-off frequency filters - just change the clock frequency - done! With SSTV there's little reason to alter the cut-off frequency, so that's not the reason to consider them here. But in terms of board space (quantity of components), cost and 8th order filtering as opposed to 4th, they're ideal. A single chip as opposed to two op-amps, four resistors, four capacitors with their tolerances and lack of easy change in cut-off frequency...a powerful incentive to use them. The only downside is providing the required clock signal, though that's usually not a big issue, besides, they have an internal clock oscillator anyway!

Steve A.

P.S. This is not a commercial! PDF follows for those interested....

MAX291-MAX296.pdf
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Sat Jul 30, 2022 9:34 am

Yes the MAX29x do make for a simple filter design, had time today to get my PCB layout done, now I need to workout how I am going to do the software for the FPGA, to drive the USB interface.

I have also made a few audio test files to work with from this site, https://sourceforge.net/projects/nbtv-design-tools/ this should keep me busy for a while.

Grant
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Re: NBTV on the Raspberry PI

Postby Steve Anderson » Sat Jul 30, 2022 1:14 pm

An example of how much easier these MAX29x devices may make things. In this case it's for SSTV demodulation filtering, off-topic maybe, but it illustrates the point.

There's also a simple in-built analogue filter in these devices for de-glitching or artifact filtering, here it's used on the output, but maybe better on the input or not used at all? The design is still in a state of flux, hence all the blue comments...

Steve A.

SSTV v4 Demodulator 3-Model.gif
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Re: NBTV on the Raspberry PI

Postby GrantXTV » Sun Jul 31, 2022 10:16 am

Hi Steve,

Looks like you are keeping busy with this project, these filters should work well for you.

Grant
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Re: NBTV on the Raspberry PI

Postby Steve Anderson » Sun Jul 31, 2022 2:16 pm

GrantXTV wrote:Looks like you are keeping busy with this project... Grant

Yep, got a break from 'real work' so taking the opportunity... I hope to make a start on the build in the next few days...then there's the software....

I'll start on the upper version above which is a known quantity, then add the lower version when I can get hold of the filter chips...

There's also all the 'blue bits' to sort out, there's quite a few more on the full schematic...

Steve A.

I'll continue this in the SSTV section where it belongs...
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