DiSEqC problems

[lawrence]

I have a universal LNB that is switched from lo-band to hi-band by sending a 22kHz tone. If I use szap to tune to a hi-band transponder then all is well. However, if I tune to a lo-band transponder then I get no lock. Scoping the signal on the coax shows the correct 13/18V but also a 0.5V p-p ~20kHz noise burst repeated every ~200uS. This appears to be confusing the LNB.

I played with the szap source and found that if I remove the call to ioctl(fd, FE_DISEQC_SEND_MASTER_CMD) then the noise burst goes away and lo-band transponders lock. To make the fix work for all apps I disabled the diseqc handler in the cx23885 driver with this patch:

Code: Select All Code

diff -purN linux-tbs-drivers.orig/linux/drivers/media//video/cx23885/cx23885-dvb.c linux-tbs-drivers/linux/drivers/media//video/cx23885/cx23885-dvb.c
--- linux-tbs-drivers.orig/linux/drivers/media//video/cx23885/cx23885-dvb.c   2011-07-17 21:43:42.000000000 +0200
+++ linux-tbs-drivers/linux/drivers/media//video/cx23885/cx23885-dvb.c   2011-09-01 13:33:08.000000000 +0200
@@ -908,6 +908,12 @@ static int dvb_register(struct cx23885_t
          dvb_attach(tbsfe_attach, fe0->dvb.frontend);
       break;
       }
+      /* There's a bug in the DiSEqC code that causes noise similar
+       * to the 22kHz tone to be constantly emitted. This prevents
+       * a simple LNB from tuning to lo-band transponders so for now
+       * disable DiSEqC
+       */
+      fe0->dvb.frontend->ops.diseqc_send_master_cmd = 0;
 
       break;
    case CX23885_BOARD_TEVII_S470:

Is this a h/w fault with this card or is this a driver bug?

This is in the latest linux-tbs-drivers_110818 built for Ubuntu 11.04 (kernel 2.6.38-10-generic #46-Ubuntu).

[deffcon]

Hi,

Can you tell me howto patch this ?

I suspect the same strange hi, low.

Maybe we can make together a good howto ?

Dave

[lawrence]

The patch is to be applied to the TBS driver before it's built.. Save the patch to a file (say ~/diseqc.patch) then cd to the directory into which you extracted the TBS drivers (e.g.~/linux-tbs-drivers) and execute:

Code: Select All Code

patch -p1 < ~/diseqc.patch

Then rebuild the drivers by running 'make && sudo make install'

NB I was advised by TBS that this problem may be a fault with my card so I returned it for exchange and am awaiting the new one.

[deffcon]

Hi,

thnx for you're quick reply, do you think its worth to try ? Maybe someone form tbsdtv can answer this question, or maybe more extensive testing for drivers. Let me know if i can help. Thnx

Dave