diff options
| author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-01 16:03:16 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-16 11:56:03 +0200 |
| commit | d12b791e3db757c42484342a015f26990642fdcb (patch) | |
| tree | 31438100fc99780df47e27ca2c67a095e14c3fc3 /drivers/media | |
| parent | [media] cxd2841er: provide signal strength for DVB-C (diff) | |
| download | linux-d12b791e3db757c42484342a015f26990642fdcb.tar.xz linux-d12b791e3db757c42484342a015f26990642fdcb.zip | |
[media] cxd2841er: adjust the dB scale for DVB-C
Instead of using a relative frequency range, calibrate it to
show the results in dB. The callibration was done getting
samples with a signal generated from -50dBm to -12dBm,
incremented in steps of 0.5 dB, using 3 frequencies:
175 MHz, 410 MHz and 800 MHz. The modulated signal was
using QAM64, and it was used a linear interpolation of all
the results.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/dvb-frontends/cxd2841er.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c index 2a698711d25b..95d82c4445e2 100644 --- a/drivers/media/dvb-frontends/cxd2841er.c +++ b/drivers/media/dvb-frontends/cxd2841er.c @@ -1768,8 +1768,13 @@ static void cxd2841er_read_signal_strength(struct dvb_frontend *fe) case SYS_DVBC_ANNEX_A: strength = cxd2841er_read_agc_gain_t_t2(priv, p->delivery_system); - p->strength.stat[0].scale = FE_SCALE_RELATIVE; - p->strength.stat[0].uvalue = strength; + p->strength.stat[0].scale = FE_SCALE_DECIBEL; + /* + * Formula was empirically determinated via linear regression, + * using frequencies: 175 MHz, 410 MHz and 800 MHz, and a + * stream modulated with QAM64 + */ + p->strength.stat[0].uvalue = ((s32)strength) * 4045 / 1000 - 85224; break; case SYS_ISDBT: strength = 65535 - cxd2841er_read_agc_gain_i( |