[linux-dvb] Getting a Twinhan 1025 DVB-S Card Working in North America

Dave Schile daveschile at hotmail.com
Thu Sep 7 18:25:08 CEST 2006


About a month ago, I got a twinhan VisionPlus 1025 DVB-S card working in my 
Linux box.  I'm sure I wouldn't have figured it out without the help of this 
list.  At the suggestion of folks who helped me get the card working, I am 
writing this little guide in hopes of helping others.  This is probably less 
a guide than  just a description of what worked for me, and what caused me 
troubles.  I only say that as a caveat that the things that I did might not 
work for you depending on myriad variables.

MY SETUP
Hardware: AMD 2800+, 512 Mb Ram,  Nvidia GPU, Twinhan VP 1025 DVB-S
OS:	2.6.17.8 Kernel, Debian testing.
Locale:	Southern California, USA

I mention my locale above because I had some problems finding the correct 
satellite to use.  I should say that before this, I had absolutely no 
experience with anything to do with satellite communication.

At first there was much confusion, I had no idea where to start, and there 
seemed to be so many different boards out there with different versions of 
software and different patches.  The first thing to do is make sure the card 
is working, or at least recognized my linux.  I won't go into kernel 
configuration, because the linuxtv wiki does that very well.

For me, the kernel was configured correctly, but the drivers didn't work 
anyway. Drivers are software that provide communication  between the card 
and the kernel/computer.  The drivers that I just mentioned are the ones 
that come in the source with the kernel (in my case kernel 2.6.17.8).  When 
loading those drivers after compiling them, the module dst couldn't identify 
my frontend. The frontend, as I understand it, is basically the tuner on the 
Twinhan card that should be spewing forth am audio/video stream.

What I had to do was download the most recent version of the v4l-dvb drivers 
from the linuxtv.org repository.  The Mercurial system they use is well 
documented on the site.  Once I got the drivers compiled and installed, the 
kernel seemed to recognize the card and the devices were all created in 
/dev/dvb/adapter0 To load the drivers, I use these commands:

# modprobe bttv card=113
# modprobe dvb-bt8xx
# modprobe dst verbose=4

The 'verbose=4' part is optional, but provides debugging information in 
dmesg to help you troubleshoot.

Now that it seemed my card was operational, the next big problem I had was 
making it operate.  Seriously, I had the hardest time figuring out how to 
tune to a transponder.  After much reading I was funneled to lyngsat.com 
where there is an full listing of all the satellites above us and what is 
available on them.  Before you even look at them, make sure you know what 
type of LNB you have.  The LNB (Low Noise Blockconverter) is that funky 
shaped thing protruding from the dish.  In my case, I was given an old 
DirecTv dish.  The key things to know about an LNB are its polarization and 
its LOF or Oscillator values.  Because much of the documentation for linuxtv 
is European, and Europe has a universal LNB with different values than here 
in America, none of the examples worked for me. So, knowing your LOF and 
polarization is important

For me, I had a circular LNB with a single LOF of 11250.
The circular refers to polarization.  This means that I will only pick up 
signals that are Left or Right in polarization.  This can be seen in the 
first column in lyngsat tables.
Next, the LOF of 11250 means that After the dish gets the signal at a very 
high frequency, It reduces that frequency by 11250 mHz so it'll travel thru 
the cable better.  Any software you use to tune your card with needs to know 
what LOF settings you have.

Once I figured out what types of satellites I could see, I went lyngsat to 
find there locations.  There are calculators on the web that will tell you 
in which direction to aim the dish.  As far as I know, with linux, there is 
no software to help you actually aim the dish, or tell you what satellite 
your pointed at.  I found it very helpful to have a sf-95 satellite finder. 
You can get these on ebay all day long for about $10.  They help alot.

Once you're dish is well-aimed at the bird, you can tune in to a 
transponder.  Go to lyngsat and get the frequency, polarization, and symbol 
rate of the transponder.  Use the scan utility to take this information and 
build a list of channels you can receive.  Make sure you're telling scan 
what your LOF is with the -l option.

Once you have the channels you use szap to tune the card to a particular 
channel.  You can use the -r  option with szap to pipe the card's output to 
the /dev/dvb/adapter0/dvr0 device.  Then you can cat this stream into your 
favorite player (as long as it can decode an mpeg2 transport stream).

Good luck!





More information about the linux-dvb mailing list