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@xxxxxxxxxxxxxxxx> --- drivers/media/dvb-frontends/cxd2841er.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c index e2f3ea55897b..6c660761563d 100644 --- a/drivers/media/dvb-frontends/cxd2841er.c +++ b/drivers/media/dvb-frontends/cxd2841er.c @@ -1746,8 +1746,13 @@ 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( -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
