[linux-dvb] Re: Siemens DVB-C HTV Finland - works!

[Jaakko Hyvätti <jaakko@hyvatti.iki.fi>]

On Tue, 15 Oct 2002, Dennis Noordsij wrote:
> But I would still like to hear from people using DVB-C cards with QAM128
> networks which values work for them :)

  106 for QAM_128 works fine with Hauppage DVB-C rev2.1.  Maybe even locks
quicker and more reliably, but that's subjective.  Also with this change,
the frequency offset I have to use at HTV cable for QAM_128 streams
becomes -0.125Mhz, not -0.25MHz that has until now been experimentally the
best.  And, when testing with dvbtune -m, the Verror values are almost
all the time 0 when using the new QAM_128 values.  Before the '106'
change, the frequency offset -0.125MHz did not lock reliably.  Now it
seems to lock well and it is of better quality!

Signal=65535, Verror=0, SNR=61680dB, BlockErrors=0, (S|L|C|V|SY|)
Signal=65535, Verror=0, SNR=61680dB, BlockErrors=0, (S|L|C|V|SY|)
Signal=65535, Verror=0, SNR=61680dB, BlockErrors=0, (S|L|C|V|SY|)

  I searched the web and found one application example where the Motel
SP5659 was used with another chip.  The IF frequency on that document was
36MHz.  I wonder if it could be the correct value to be used here too?
The 0.125MHz offset looks very much the same as my experimentally found
offset.

  So my currently best working options are in the patch below.  Maybe by
working with the qam values we can find even better combinations..  Maybe
we should have an automatic program that tries to find the best ones with
genetical algorithms? :-)

Regards,
Jaakko

Index: driver/frontends/ves1820.c
===================================================================
RCS file: /cvs/linuxtv/DVB/driver/frontends/ves1820.c,v
retrieving revision 1.7
diff -u -r1.7 ves1820.c
--- driver/frontends/ves1820.c	15 Oct 2002 10:40:36 -0000	1.7
+++ driver/frontends/ves1820.c	15 Oct 2002 11:41:38 -0000
@@ -147,6 +147,23 @@
  *   set up the downconverter frequency divisor for a
  *   reference clock comparision frequency of 62.5 kHz.
  */
+
+/*
+ *   Tuner Mitel SP5659 (tuner_type==1)
+ *   buf[2]: 1  2^16  2^15  PE  R3  R2  R1  R0
+ *           1     0     0   0   0   1   0   1
+ *   PE = prescaler, enables 2.7GHz operation.  Not needed, set to 0
+ *   2^16, 2^15 = high bits of divider
+ *   R3..0 = division ratio, 0101 = 64, corresponds to comp. freq 62.5kHz
+ *           with 4MHz external reference.
+ *   buf[3]: C1   C0   RE  RTS   P3   P2/TS2 P1/TS1 P0/TS0
+ *            1    0    0    0    0       1     0     0
+ *   C1,0 = charge pump current, 10 = +-555µA
+ *   RE = REF/COMP output enable
+ *   RTS = 0=REF output, 1=COMP output.  (RE,RTS)=(0,0) = normal operation.
+ *   TS2..0 = test mode control bits
+ *   P3..0 = port P3..0 output, 1000 (<174MHz), 0100 (<470MHz), 0001 (>470MHz)
+ */
 static
 int tuner_set_tv_freq (struct dvb_frontend *frontend, u32 freq)
 {
@@ -156,7 +173,7 @@
 	int tuner_type = GET_TUNER(frontend);
         u8 buf [4];

-	div = (freq + 36125000) / 62500;
+	div = (freq + 36000000) / 62500;
 	buf[0] = (div >> 8) & 0x7f;
 	buf[1] = div & 0xff;
 	buf[2] = byte3[tuner_type];
@@ -170,6 +187,11 @@
 			  freq < 454000000 ? 0x92 : 0x34);
 	}

+	dprintk ("%s: tuning to %u.%06u MHz\n",
+		 __FILE__,
+		 (div * 62500 - 36000000) / 1000000,
+		 (div * 62500 - 36000000) % 1000000);
+
         return tuner_write (frontend->i2c, addr[tuner_type], buf);
 }

@@ -359,7 +381,7 @@
         {  QAM_16,  16, 140, 164, 162, 145 },
         {  QAM_32,  32, 140, 120, 116, 150 },
         {  QAM_64,  64, 106,  70,  67, 106 },
-        { QAM_128, 128, 120,  54,  52, 126 },
+        { QAM_128, 128, 106,  54,  52, 126 },
         { QAM_256, 256,  92,  38,  35, 107 }
 };

@@ -533,3 +555,7 @@
 MODULE_LICENSE("GPL");
 MODULE_PARM(debug,"i");

+
+// Local variables:
+// c-basic-offset: 8
+// End:

-- 
Foreca Ltd                                           Jaakko.Hyvatti@foreca.com
Pursimiehenkatu 29-31 B, FIN-00150 Helsinki, Finland     http://www.foreca.com




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