Poor Short-Sighted Man’s DATV system for Windows

[G4EWJ]

Building on the excellent work of F4DAY, Rob M0DTS and others, I’ve been working on a variation of the system, which produces live video using Windows. With help from several of this parish, this is now undergoing field trials.

The system uses a free PVR program http://www.gbpvr.com and the Hauppauge PVRx50 / USB range of video capture devices.

I’ve written a single Windows program which reads data from the end of the file produced by GBPVR and converts it into a transport stream which it sends over the USB port to the serialiser. It uses much less cpu time than the current Linux setup. At 4MS/s, it takes about 3% of cpu time on my 2.3GHz Core2 Duo. Rob has run it at 4MS/s on his 700MHz laptop where it takes 14% of cpu time. It has been written to be able to multiplex several program inputs together, although that needs more work and is not currently available.

It works with the current serialiser as used by Rob, which has fixed 1/2 FEC processing. I’ve built a new, faster serialiser using an FT2232H module, which can do all the FECs, although the Windows program can do all the FECs itself. I think it should be possible to get it up to 8MS/s. I’m running at 5MS/s at the moment as I don’t have Nyquist filters to go any higher. It uses 2 chips plus the FT2232H USB module, on a single-sided PCB. The FIFO is 13kB. There’s a configuration utility to set up the symbol rate, FEC, PIDs and programme info.

The Short-Sighted reference is because I’ve tried to use through-hole components as much as possible. The new serialiser is through-hole, apart from an SD card socket which is an SMD, although not too difficult at 2mm pin spacing. Pre-processed transport stream files can be played off the SD card. This isn’t working on the new MK2 serialiser as yet. The new MK1 serialiser was SD card only with no PC connection and I have yet to move the SD card functionality to the MK2.

I estimate that the serialiser will cost about £40-45 to build. The FT2232H module makes it expensive, but I can hardly see the pins on the FT2232H chip, never mind solder them.

I’ve built a modulator based on the RF2480 chip which is 1.27mm pin spacing. It needs more work and as I’m much happier with digital rather than analogue, I’m hoping I can persuade someone to take that on.

If anyone would like to help with the testing and try the Windows software with their PMDATV hardware, please let me know. If you can make your own PCBS, I can give you the artwork for the new serialiser. Rob has kindly agreed to host all the details on his web site. Hardware and software files will appear there in time. In the meantime, please contact me directly here or via my callsign at mem dot batc dot org dot uk.

Brian

[G4GUO]

Keep up the good work Brian.

I actually find being shorted sighted an advantage when working
on surface mount stuff.

- Charles

[G4EWJ]

Yes, it should be long-sighted really, but it doesn't have the same ring to it.

Brian

[g8byi]

Hi to All.
Just to confirm great results from Brians PSMDATV Windows based system both at 2Ms/s and 4Ms/s using Robs (M0DTS) serializer and IQ Modulator circuits. PC a dual core 2.8ghz only using 3% of processor time. I had very good results from Rob's Linux based system, but this one is much easier to get going, (I was a Linux virgin so had a steep learning curve in Ubuntu usage).
Well done to you both....
73
Richard G8BYI

[G4IMO]

Update on my Datv - Currently testing Brians new windows Datv software. Running SR 2000 on Robs serialiser produces excellent results on live video. CPU use only 10% on this Dell 2.8GHz single core machine. This PC could not run the linux software as the CPU was over 100%. Many thanks for all the excellent work done by Brian and Rob to get a working system.

Nick
G4IMO

[G1LWX]

I have just finished building the Poor Short-Sighted Man's DATV system for Windows based on Brians G4EWJ software and serialiser, and Robs M0DTS modulator board.
First results are excellent using XP with an Athlon 1.9 CPU and single Hard Drive it uses 23% of processor time.
I can recommend this system to anyone wanting to get going on digital.

[g7lwt]

Further to Mike's post above, here are some screen shots showing the constellation and BER for the his DVB TX (as received at IO83SO). The screen shots progress from 50mW to 5W; watch the constellation tighten up at 5 W, even after the BER has dropped to zero at 200 mW:









Original images hosted here: http://www.g7lwt.com/documents/datv/g1lwx/ Sadly the Reed Solomon and Viterbi BERs on the screen shots above have been truncated by the BBS.

The constellation from G1LWX's home brew project compares very favourably with similar strength signals from an SR-Systems D-ATV TX. Congratulations to Brian and Mike!

NB. The software analyser is Tutioune from F6ZDP, using a cheap TechnoTrend DVS-S2 card http://www.vivadatv.org/ The latest version of Tutioune allows the BER and constellation to be viewed remotely via the WWW: http://www.vivadatv.org/tutioune.php?om ... ation_id=1 Currently monitoring GB3TM "just in case"...

73 de Darren
G7LWT

[G4GUO]

Thanks for that information Darren I have a TT S-3600 DVB-S2 USB device that I bought for testing my C++ implementation
of DVB-S2. Although F6DZP's S/W does not support DVB-S2 and my receiver is a USB2 device rather than a PCI device
there is hope!!

Off to investigate!

- Charles G4GUO

[g7lwt]

Hi Charles,

Tutioune seems to work best with a custom driver for the SAA7146A but you could try TSReader (lite) with the TechnoTrend USB RX:

http://www.tsreader.com/tsreader/index.html

73 de Darren
G7LWT

[G4GUO]

Hi Darren,

My biggest problem is that my Win7 PC is 64 bit and it needs signed 64bit drivers it won't
work with 32 bit drivers.
I know I can hit F8 during bootup to disable the signing check but that is a bit of a pain and
doesnt solve the 64/32 bit problem.

I have used the BDA drivers that came with the S-3600 and they work however when I
set the symbol rate at 4M the viewing program locks up. I have not tried it with GraphEdit.

I managed to get the S-3600 to work under Linux so I suspect my best bet will be to
look at the docs for the Linux driver and see what I can configure/read then write a simple program
to control the card myself under Linux.

I had also thought of swapping the motherboard in my Linux PC with one that has many more PCI slots
but all the ones I could find that have the same processor socket and memory type now seem to be
obsolete! My Linux machine has a Core 2 Quad processor and DDR2 memory which is considered a bit
old now.

- Charles