Manu Abraham wrote:
> Hi all,
>
> would it make sense to initially lock with a larger loop bandwidth
> (for a faster lock) and once locked, switch to a smaller loop
> bandwidth (for lower phase noise) ?
>
If you mean the lock of the tuner-pll, I did it for the cinergy DVB-C card:
diff -r e625163eba29 linux/drivers/media/dvb/ttpci/budget-av.c
--- a/linux/drivers/media/dvb/ttpci/budget-av.c Sat Jan 20 15:53:08
2007 -0200
+++ b/linux/drivers/media/dvb/ttpci/budget-av.c Sun Jan 21 09:54:15
2007 +0100
@@ -633,6 +633,7 @@ static int philips_cu1216_tuner_set_para
struct budget *budget = (struct budget *) fe->dvb->priv;
u8 buf[4];
struct i2c_msg msg = {.addr = 0x60,.flags = 0,.buf = buf,.len =
sizeof(buf) };
+ int i;
#define TUNER_MUL 62500
@@ -640,7 +641,7 @@ static int philips_cu1216_tuner_set_para
buf[0] = (div >> 8) & 0x7f;
buf[1] = div & 0xff;
- buf[2] = 0x86;
+ buf[2] = 0xce;
buf[3] = (params->frequency < 150000000 ? 0x01 :
params->frequency < 445000000 ? 0x02 : 0x04);
@@ -648,6 +649,29 @@ static int philips_cu1216_tuner_set_para
fe->ops.i2c_gate_ctrl(fe, 1);
if (i2c_transfer(&budget->i2c_adap, &msg, 1) != 1)
return -EIO;
+
+ msg.flags = I2C_M_RD;
+ msg.len = 1;
+ for (i = 0; i < 20; i++) {
+ if (fe->ops.i2c_gate_ctrl)
+ fe->ops.i2c_gate_ctrl(fe, 1);
+ if (i2c_transfer(&budget->i2c_adap, &msg, 1) == 1 && (buf[0] &
0x40))
+ break;
+ msleep(10);
+ }
+
+ msg.flags = 0;
+ msg.buf = &buf[2];
+ msg.len = 2;
+ buf[2] &= ~0x40;
+ if (fe->ops.i2c_gate_ctrl)
+ fe->ops.i2c_gate_ctrl(fe, 1);
+ if (i2c_transfer(&budget->i2c_adap, &msg, 1) != 1)
+ return -EIO;
+
+ printk("(%s:%d)Loops %d, Status %02x, Frequency %d.%dMHz\n",
+ __FILE__, __LINE__, i, buf[0], params->frequency / 1000000,
(params->frequency / 100000) % 10);
+
return 0;
}
Many pll chips have an auto-switch feature. It isn't necessary to switch
the charge pump current manually. It may be a problem, that many tune
functions do never wait for the lock. This is not a problem if the time
for the lock is lower than the time for initializing the demodulator.
For the patch above, I get one loop for switching some channels forward
or backward. I get 2..3 loops for switching from the highest channel on
VHFH to the lowest channel on UHF.
Another nice feature is the AGC time constant and the AGC take-over
point. The AGC values are never programed for the Cinergy card. The
reset values are used always.
- Hartmut
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