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Allow setting bandwidth for R820T

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This improves SDR performence for nearby channel interference.
As a sideeffect also improves dynamic range becase ADC is not overloaded
by onwanted singlas.

Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Jiří Pinkava 2015-03-17 13:19:20 +01:00 committed by Steve Markgraf
parent d447a2e983
commit d892279085
3 changed files with 93 additions and 2 deletions
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1
include/tuner_r82xx.h
View File

@ -115,5 +115,6 @@ int r82xx_standby(struct r82xx_priv *priv);
int r82xx_init(struct r82xx_priv *priv);
int r82xx_set_freq(struct r82xx_priv *priv, uint32_t freq);
int r82xx_set_gain(struct r82xx_priv *priv, int set_manual_gain, int gain);
int r82xx_set_bandwidth(struct r82xx_priv *priv, int bandwidth, uint32_t rate);
#endif

18
src/librtlsdr.c
View File

@ -126,6 +126,7 @@ struct rtlsdr_dev {
};
void rtlsdr_set_gpio_bit(rtlsdr_dev_t *dev, uint8_t gpio, int val);
static int rtlsdr_set_if_freq(rtlsdr_dev_t *dev, uint32_t freq);
/* generic tuner interface functions, shall be moved to the tuner implementations */
int e4000_init(void *dev) {
@ -238,7 +239,20 @@ int r820t_set_freq(void *dev, uint32_t freq) {
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
return r82xx_set_freq(&devt->r82xx_p, freq);
}
int r820t_set_bw(void *dev, int bw) { return 0; }
int r820t_set_bw(void *dev, int bw) {
int r;
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
r = r82xx_set_bandwidth(&devt->r82xx_p, bw, devt->rate);
if(r < 0)
return r;
r = rtlsdr_set_if_freq(devt, r);
if (r)
return r;
return rtlsdr_set_center_freq(devt, devt->freq);
}
int r820t_set_gain(void *dev, int gain) {
rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
return r82xx_set_gain(&devt->r82xx_p, 1, gain);
@ -670,7 +684,7 @@ int rtlsdr_deinit_baseband(rtlsdr_dev_t *dev)
return r;
}
int rtlsdr_set_if_freq(rtlsdr_dev_t *dev, uint32_t freq)
static int rtlsdr_set_if_freq(rtlsdr_dev_t *dev, uint32_t freq)
{
uint32_t rtl_xtal;
int32_t if_freq;

76
src/tuner_r82xx.c
View File

@ -1073,6 +1073,82 @@ int r82xx_set_gain(struct r82xx_priv *priv, int set_manual_gain, int gain)
return 0;
}
/* Bandwidth contribution by low-pass filter. */
static const int r82xx_if_low_pass_bw_table[] = {
1700000, 1600000, 1550000, 1450000, 1200000, 900000, 700000, 550000, 450000, 350000
};
#define FILT_HP_BW1 350000
#define FILT_HP_BW2 380000
int r82xx_set_bandwidth(struct r82xx_priv *priv, int bw, uint32_t rate)
{
int rc;
unsigned int i;
int real_bw = 0;
uint8_t reg_0a;
uint8_t reg_0b;
if (bw > 7000000) {
// BW: 8 MHz
reg_0a = 0x10;
reg_0b = 0x0b;
priv->int_freq = 4570000;
} else if (bw > 6000000) {
// BW: 7 MHz
reg_0a = 0x10;
reg_0b = 0x2a;
priv->int_freq = 4570000;
} else if (bw > r82xx_if_low_pass_bw_table[0] + FILT_HP_BW1 + FILT_HP_BW2) {
// BW: 6 MHz
reg_0a = 0x10;
reg_0b = 0x6b;
priv->int_freq = 3570000;
} else {
reg_0a = 0x00;
reg_0b = 0x80;
priv->int_freq = 2300000;
if (bw > r82xx_if_low_pass_bw_table[0] + FILT_HP_BW1) {
bw -= FILT_HP_BW2;
priv->int_freq += FILT_HP_BW2;
real_bw += FILT_HP_BW2;
} else {
reg_0b |= 0x20;
}
if (bw > r82xx_if_low_pass_bw_table[0]) {
bw -= FILT_HP_BW1;
priv->int_freq += FILT_HP_BW1;
real_bw += FILT_HP_BW1;
} else {
reg_0b |= 0x40;
}
// find low-pass filter
for(i = 0; i < ARRAY_SIZE(r82xx_if_low_pass_bw_table); ++i) {
if (bw > r82xx_if_low_pass_bw_table[i])
break;
}
--i;
reg_0b |= 15 - i;
real_bw += r82xx_if_low_pass_bw_table[i];
priv->int_freq -= real_bw / 2;
}
rc = r82xx_write_reg_mask(priv, 0x0a, reg_0a, 0x10);
if (rc < 0)
return rc;
rc = r82xx_write_reg_mask(priv, 0x0b, reg_0b, 0xef);
if (rc < 0)
return rc;
return priv->int_freq;
}
#undef FILT_HP_BW1
#undef FILT_HP_BW2
int r82xx_set_freq(struct r82xx_priv *priv, uint32_t freq)
{
int rc = -1;