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V4L/DVB (12887): DIB7000P: SNR calcuation forr DiB7000P

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Add the SNR monitoring for the dib7000p. The result is in dB.

Signed-off-by: Olivier Grenie <olivier.grenie@dibcom.fr>
Signed-off-by: Patrick Boettcher <patrick.boettcher@dibcom.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Olivier Grenie 2009-09-15 06:46:52 -03:00 committed by Mauro Carvalho Chehab
parent 74b76f2136
commit ef80196490
1 changed files with 32 additions and 1 deletions
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33
drivers/media/dvb/frontends/dib7000p.c
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@ -10,6 +10,7 @@
#include <linux/kernel.h>
#include <linux/i2c.h>
#include "dvb_math.h"
#include "dvb_frontend.h"
#include "dib7000p.h"
@ -1217,7 +1218,37 @@ static int dib7000p_read_signal_strength(struct dvb_frontend *fe, u16 *strength)
static int dib7000p_read_snr(struct dvb_frontend* fe, u16 *snr)
{
*snr = 0x0000;
struct dib7000p_state *state = fe->demodulator_priv;
u16 val;
s32 signal_mant, signal_exp, noise_mant, noise_exp;
u32 result = 0;
val = dib7000p_read_word(state, 479);
noise_mant = (val >> 4) & 0xff;
noise_exp = ((val & 0xf) << 2);
val = dib7000p_read_word(state, 480);
noise_exp += ((val >> 14) & 0x3);
if ((noise_exp & 0x20) != 0)
noise_exp -= 0x40;
signal_mant = (val >> 6) & 0xFF;
signal_exp = (val & 0x3F);
if ((signal_exp & 0x20) != 0)
signal_exp -= 0x40;
if (signal_mant != 0)
result = intlog10(2) * 10 * signal_exp + 10 *
intlog10(signal_mant);
else
result = intlog10(2) * 10 * signal_exp - 100;
if (noise_mant != 0)
result -= intlog10(2) * 10 * noise_exp + 10 *
intlog10(noise_mant);
else
result -= intlog10(2) * 10 * noise_exp - 100;
*snr = result / ((1 << 24) / 10);
return 0;
}