Using TBS6925 with eumetcast (Eumetsat) configuration

[MarcoLazzeri]

Did anybody try to use tbs6925 in a linux environment to get satellite data provided by eumetcast?
I use Debian GNU/Linux 7.7 (wheezy) distribution and I have properly compiled and installed the tbs drivers (v141019) and the card works. Until December the 31st Eumetcast will use DVB-S method to deliver data using Eurobird9 (11977MHz, horizontal polarization, symbol rate 27500, service id 231) in parallel with DVB-S2 method. After that only DVB-S2 method will be available. Eumetsat has a web page about this migration and it provides satellite parameters to tune the receiver (http://www.eumetsat.int/website/home/Te ... 82113.html). So I wrote up a "channels.conf" file to use with szap-s2 provided with the tbs drivers:

eurobird9:11977:h:0:27500:0:0:231
Eutelsat 10A:11263:hC35S1M5O20:0:33000::::

The first line is the old dvb-s configuration and the second could be (as what I understood) the new dvb-s2 configuration.
But...
./tbs/szap-s2/szap-s2 -c /etc/channels.conf -n1 -H
zapping to 1 'eurobird9':
delivery DVB-S, modulation QPSK
sat 0, frequency 11977 MHz H, symbolrate 27500000, coderate auto, rolloff 0.35
mis -1, vpid 0x1fff, apid 0x1fff, sid 0x00e7
status 00 | signal 58% | snr 74% | ber 0 | unc 0 |
status 1f | signal 58% | snr 74% | ber 0 | unc 0 | FE_HAS_LOCK (it works)

./tbs/szap-s2/szap-s2 -c /etc/channels.conf -n2 -H -m1
reading channels from file '/etc/channels.conf'
zapping to 2 'Eutelsat 10A':
delivery DVB-S2, modulation 8PSK
sat 0, frequency 11263 MHz H, symbolrate 33000000, coderate 3/5, rolloff 0.20
mis 1, vpid 0x1fff, apid 0x1fff, sid 0x0000
status 00 | signal 55% | snr 37% | ber 1 | unc 0 |
status 00 | signal 55% | snr 37% | ber 1 | unc 0 | (and so on... It does not work)

Is the configuration in channels.conf correct?
I have to say that my satellite dish does not point toward 10E but it still points to 9E. In a guide about migration Eumetsat says that it could be possible to receive the signal even with the dish pointing to the old satellite. Looking at szap-s2 output it seems to me that I have a SNR too low in the dvb-s2 case. Maybe is this the reason that does not let the service to be locked? Can it be solved by repointing the satellite dish?

Thank you very much for the attention and, please, apologize me for the length of this post.

[MarcoLazzeri]

I did some more experiments with this card to receive eumetcast DVB-S2 basic service.
We pointed the satellite dish to eutelsat 10E and the reception is now better. We can lock the signal but we are still loosing many frames. The command szap-s2 reports a 58% signal rate and a 75% snr. I set up the roloff on "AUTO".
Maybe we have to do some fine tuning on the dish position. I hope so because in this situation the service is not useful...
I will update this post if I will have some news
P.S.: Eumetsat now claims that this card is suitable to receive the basic service but there is no documentation on the linux side

[crazycat]

For better reception BS service only need set modcode filter for 8psk, 3/5 only. Otherwise you have packet losts if snr < ~9.8dB ( for stable reception bs&hvs you need big dish 1.5m+ ).

P.S. Eumetcast linux guide for Technisat cards suitable for another supported, because pointed to same my drivers based on original tbs linux drivers.

[MarcoLazzeri]

Thank you for the reply, crazycat. We still have receiving problem even fine tuning the dish. We have a 1.8m satellite dish!!! It seems that signal rate could not be increased more than 58% (I used femon with -H switch to monitor these parameters). We even changed the LNB but the result is still the same. Crazycat, I have seen that you pointed out that with an snr < ~9.8dB I wold have many packet loss. Is it my case? How can I switch from szap-s2 or femon percentage to dB? Is my snr expressed in dB simply -10log(0.75) (providing that femon output for snr is 75%)?
Thank you very much.
Marco

[crazycat]

You use original TBS linux drivers ? For correct reception Eumetcast DVB-S2 need disable TS FIFO regulation, see README_EUMETCAST:

EUMETSAT DVB-S2 service reception

In order to receive EUMETSAT DVB-S2 service you need supported TBS card model.
At the moment that means TBS 5925, TBS 6925 or the latest TBS 6983.

If you want to use TBS 5925 or TBS 6925 you need to de-activate "issy" module
parameter of stv090x driver. one of the easiest way to do that is to create
file in /etc/modprobe.d directory, named for example "stv090x.conf" with
the following content:

# cat /etc/modprobe.d/stv090x.conf
options stv090x issy=0

and on the next driver load the new setting will take affect.

If you use my fork of TBS linux drivers - use another option ts_nosync=1:

Code: Select All Code

options stv090x ts_nosync=1

And stv090x driver report signal level as 100+RFLevel (dBm) and SNR as snr(dB)*5. So if you have SNR ~75% - this is 15dB, good result for 1.5-1.8m dish.

[MarcoLazzeri]

Hi Crazycat, thank you for your further infos.
I am using the tbs drivers downloaded from this site, so I think they are the original ones (they are not the last release - 141225 - but the previous one). I read the README_EUMETCAST so I put the file to disable the issy module as you pointed out. My configuration for the service is the following one:
Eutelsat 10A:11263:hC35S1M5O0:0:33000:::
while the szap-s2 comand line I use is this one:
szap-s2 -m 1 -c /etc/channels.conf -n 1
provided that /etc/channels.conf has the previous definition for the service in its first line.
I added the switch "-m 1" because README_EUMETCAST warns about this option and the eumetsat documentation indicates an ISI=1 in the satellite transponder characteristics. (BTW I can lock the service both using -m 1 or not)

Marco

[crazycat]

I think you need realign dish to 10E for maximum signal, or disable HVS reception (set modcode to 8psk,3/5 only).

P.S. ISI filteriung not need, because only one ISI=1.

[MarcoLazzeri]

Some updates for this topic...
After a full afternoon spent to fine tuning the antenna (without enhancements on the reception side) I wrote to Eumetsat helpdesk describing my situation. They answered that the tbs6925 was not in the list of the devices they tested so they could not give me any hints. A couple of days later I noticed that in the Eumetsat page about the migration to DVB-S2 an installation guide for some tbs cards under linux had been added, including the tbs6925. So I followed the guide changing the drivers version from the official one to the one suggested by the guide (v.a913a74100d5 by CrazyCat) but without any improvement.
Finally we bought a PCI-e sky star 2 express card and with this card everything is fine. femon -H reports a 69% signal level compared with the 57% of the tbs 6925. Are the card based on a different chipset? I will write to Eumetsat asking for some additional infos. I think that the only tbs card they tested for linux id the 6983 even if, in my opinion, the table of the compatibility list is a bit hambiguous.
Ok, I hope that this post could be useful to somebody.
If crazycat has additional infos about the card they are welcome
Marco

[crazycat]

SS2 eXpress HD, SS HD USB, TBS 5980 (QBox-CI) based on STV0903BAC demod. This broadcast version of STV090x demod family, but have restricted DVB-S2 VCM support - so can receive EUMETcast BS service only with maximum link margin and not need modcode selection.

For TBS 5925/6925 need disable HVS reception in your case, because you have bad signal. Modcode selection for stv090x driver not implemented yet in TBS linux drivers, but possible simple solution - init demod to dual mode and avoid 16/32APSK support.

So before compiling linux-tbs-drivers you need edit some driver sources.
For TBS 6925/6926:
linux-tbs-drivers/linux/drivers/media/common/saa716x/saa716x_tbs.c:

Code: Select All Code

....
#define SAA716x_MODEL_TURBOSIGHT_TBS6925 "TurboSight TBS 6925"
#define SAA716x_DEV_TURBOSIGHT_TBS6925   "DVB-S/S2"

static struct stv090x_config stv0900_config = {
   .device      = STV0900,
   .demod_mode   = STV090x_SINGLE,
   .clk_mode   = STV090x_CLK_EXT,

   .xtal      = 27000000,
   .address   = 0x68,

   .ts1_mode   = STV090x_TSMODE_PARALLEL_PUNCTURED,
   .ts2_mode   = STV090x_TSMODE_PARALLEL_PUNCTURED,

   .repeater_level      = STV090x_RPTLEVEL_16,

   .adc1_range   = STV090x_ADC_2Vpp,
   .tuner_bbgain   = 8,

   .tuner_get_frequency   = stb6100_get_frequency,
   .tuner_set_frequency   = stb6100_set_frequency,
   .tuner_set_bandwidth   = stb6100_set_bandwidth,
   .tuner_get_bandwidth   = stb6100_get_bandwidth,

   .tun1_iqswap=1,
   .tun2_iqswap=1,
};
....

For "exotic" TBS 6925C:
linux-tbs-drivers/linux/drivers/media/video/cx23885/cx23885-dvb.c

Code: Select All Code

....
static struct stv6110_config netup_stv6110_tunerconfig_b = {
   .i2c_address = 0x63,
   .mclk = 16000000,
   .clk_div = 1,
   .gain = 8, /* +16 dB  - maximum gain */
};

static struct stv090x_config stv0900_config = {
   .device      = STV0900,
   .demod_mode   = STV090x_SINGLE,
   .clk_mode   = STV090x_CLK_EXT,

   .xtal      = 27000000,
   .address   = 0x68,

   .ts1_mode   = STV090x_TSMODE_PARALLEL_PUNCTURED,
   /* .ts2_mode   = STV090x_TSMODE_PARALLEL_PUNCTURED, */

   .repeater_level      = STV090x_RPTLEVEL_16,

   .tuner_get_frequency   = stb6100_get_frequency,
   .tuner_set_frequency   = stb6100_set_frequency,
   .tuner_set_bandwidth   = stb6100_set_bandwidth,
   .tuner_get_bandwidth   = stb6100_get_bandwidth,
};
....

For TBS 5925:
linux-tbs-drivers/linux/drivers/media/dvb/dvb-usb/tbs5925.c

Code: Select All Code

....
static struct stv090x_config stv0900_config = {
   .device         = STV0900,
   .demod_mode     = STV090x_SINGLE,
   .clk_mode       = STV090x_CLK_EXT,

   .xtal           = 27000000,
   .address        = 0x68,

   .ts1_mode       = STV090x_TSMODE_DVBCI,
   .ts2_mode       = STV090x_TSMODE_SERIAL_CONTINUOUS,
   
   .repeater_level         = STV090x_RPTLEVEL_16,

   .adc1_range   = STV090x_ADC_2Vpp,
   .tuner_bbgain   = 8,

   .tuner_get_frequency    = stb6100_get_frequency,
   .tuner_set_frequency    = stb6100_set_frequency,
   .tuner_set_bandwidth    = stb6100_set_bandwidth,
   .tuner_get_bandwidth    = stb6100_get_bandwidth,
....

So you must change STV090x_SINGLE to STV090x_DUAL.

[crazycat]

femon -H reports a 69% signal level compared with the 57% of the tbs 6925.

Signal levels not comparable, because devices based on diffrent tuner ICs - STV6110a in Technisat and STB6100 in 6925.
So you must compare SNR.