[linux-dvb] Getting a Twinhan 1025 DVB-S Card Working in North
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.
Hardware: AMD 2800+, 512 Mb Ram, Nvidia GPU, Twinhan VP 1025 DVB-S
OS: 126.96.36.199 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 188.8.131.52). 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).
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