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soapy: fix SDRplay RSP1B gain (stream fails to start; gain runs backwards) #331

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soapy: fix SDRplay RSP1B gain (stream fails to start; gain runs backwards) #331

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85 changes: 79 additions & 6 deletions sdr_soapy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,37 @@ static struct {

SoapySDRRange gain_range;
int current_gain_step;

int sdrplay_lna_max; // >= 0: SDRplay model in sdrplay_models[], highest LNA state at 1090 MHz;
// total gain is then set through IFGR/RFGR here (soapySetTotalGain())
} SOAPY;

// SDRplay devices through SoapySDRPlay3: both gain elements are gain *reductions*
// (IFGR = IF gain reduction in dB, 20..59; RFGR = LNA state, higher = more
// attenuation), so SoapySDR's generic total gain runs backwards: its maximum is the
// least gain. The module also reports one RFGR range per model, for all bands, but
// fewer LNA states exist in L-band (1000-2000 MHz); at 1090 MHz the top of the
// reported range is not valid, and sdrplay_api_Init() fails with it (seen on the
// RSP1B: RFGR 9). For the models below dump1090 maps its own total gain onto the
// two elements. Other models keep the generic mapping.
#define SDRPLAY_IFGR_MIN 20
#define SDRPLAY_IFGR_MAX 59

static const struct {
const char *hw_key; // SoapySDRPlay3 hardware key
int lna_max; // highest LNA state in L-band
} sdrplay_models[] = {
{ "RSP1B", 8 }, // 9 L-band LNA states; tested on hardware

// Needs testing on hardware before enabling. L-band LNA state counts from the
// SDRplay API 3.15 headers:
// { "RSP1A", 8 }, // needs testing: RSPIA_NUM_LNA_STATES_LBAND 9 (sdrplay_api_rsp1a.h)
// { "RSPduo", 8 }, // needs testing: RSPDUO_NUM_LNA_STATES_LBAND 9 (sdrplay_api_rspDuo.h)
// { "RSPdx", 18 }, // needs testing: RSPDX_NUM_LNA_STATES_LBAND 19 (sdrplay_api_rspDx.h)
// RSP1, RSP2 and RSPdx-R2: no L-band figure in the headers; need the LNA state
// count at 1090 MHz and testing
};

// Polyfill some differences between SoapySDR 0.7 and 0.8
#if !defined(SOAPY_SDR_API_VERSION) || (SOAPY_SDR_API_VERSION < 0x00080000)

Expand Down Expand Up @@ -79,6 +108,40 @@ static SoapySDRStream *polyfill_SoapySDRDevice_setupStream(SoapySDRDevice *devic
// =============================== SoapySDR handling ==========================
//

// Set the total gain: the device's own mapping, except on the SDRplay models above,
// where the gain below the maximum is taken off IFGR first (keeping the LNA at full
// gain for the noise figure) and then off the LNA. Returns 0 on success.
static int soapySetTotalGain(double gain)
{
if (SOAPY.sdrplay_lna_max < 0)
return SoapySDRDevice_setGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, gain) < 0 ? -1 : 0;

const int ifgr_span = SDRPLAY_IFGR_MAX - SDRPLAY_IFGR_MIN;
int reduction = (int) round(SOAPY.gain_range.maximum - gain);
if (reduction < 0)
reduction = 0;
if (reduction > ifgr_span + SOAPY.sdrplay_lna_max)
reduction = ifgr_span + SOAPY.sdrplay_lna_max;

const int ifgr = SDRPLAY_IFGR_MIN + (reduction < ifgr_span ? reduction : ifgr_span);
const int lna = reduction - (ifgr - SDRPLAY_IFGR_MIN);
if (SoapySDRDevice_setGainElement(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, "IFGR", ifgr) != 0 ||
SoapySDRDevice_setGainElement(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, "RFGR", lna) != 0)
return -1;
return 0;
}

// The total gain on the same scale as soapySetTotalGain()
static double soapyGetTotalGain(void)
{
if (SOAPY.sdrplay_lna_max < 0)
return SoapySDRDevice_getGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel);

const double ifgr = SoapySDRDevice_getGainElement(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, "IFGR");
const double lna = SoapySDRDevice_getGainElement(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, "RFGR");
return SOAPY.gain_range.maximum - ((ifgr - SDRPLAY_IFGR_MIN) + lna);
}

void soapyInitConfig()
{
SOAPY.dev = NULL;
Expand All @@ -91,6 +154,7 @@ void soapyInitConfig()
SOAPY.enable_agc = false;
SOAPY.num_gain_elements = 0;
SOAPY.gain_elements = NULL;
SOAPY.sdrplay_lna_max = -1;
SOAPY.num_settings = 0;
SOAPY.settings = NULL;
}
Expand Down Expand Up @@ -214,12 +278,14 @@ bool soapyOpen(void)
}
SoapySDRKwargs_clear(&result);

bool is_sdrplay = false;
char* driver_key = SoapySDRDevice_getDriverKey(SOAPY.dev);
if (driver_key) {
fprintf(stderr, "soapy: driver key: %s\n", driver_key);

// Apply driver-specific defaults
if (!strcmp(driver_key, "SDRplay")) {
is_sdrplay = true;
// Default to 5MHz bandwidth
if (SOAPY.bandwidth == 0)
SOAPY.bandwidth = 5.0e6;
Expand All @@ -231,6 +297,9 @@ bool soapyOpen(void)
char* hw_key = SoapySDRDevice_getHardwareKey(SOAPY.dev);
if (hw_key) {
fprintf(stderr, "soapy: hardware key: %s\n", hw_key);
for (size_t i = 0; is_sdrplay && i < sizeof(sdrplay_models) / sizeof(sdrplay_models[0]); i++)
if (!strcmp(hw_key, sdrplay_models[i].hw_key))
SOAPY.sdrplay_lna_max = sdrplay_models[i].lna_max;
SoapySDR_free(hw_key);
}

Expand Down Expand Up @@ -298,6 +367,11 @@ bool soapyOpen(void)
}

SOAPY.gain_range = SoapySDRDevice_getGainRange(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel);
if (SOAPY.sdrplay_lna_max >= 0) {
SOAPY.gain_range.minimum = 0;
SOAPY.gain_range.maximum = (SDRPLAY_IFGR_MAX - SDRPLAY_IFGR_MIN) + SOAPY.sdrplay_lna_max;
SOAPY.gain_range.step = 1;
}
if (SOAPY.gain_range.step <= 0)
SOAPY.gain_range.step = 1.0;
else if (SOAPY.gain_range.step <= 0.1)
Expand Down Expand Up @@ -326,7 +400,7 @@ bool soapyOpen(void)
}

double gain = (Modes.gain == MODES_DEFAULT_GAIN ? SOAPY.gain_range.maximum : Modes.gain);
if (SoapySDRDevice_setGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, gain) < 0) {
if (soapySetTotalGain(gain) != 0) {
fprintf(stderr, "soapy: setGain(%.1fdB) failed\n", gain);
goto error;
}
Expand Down Expand Up @@ -355,7 +429,7 @@ bool soapyOpen(void)
}
}

SOAPY.current_gain_step = (int) round( (SoapySDRDevice_getGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel) - SOAPY.gain_range.minimum) / SOAPY.gain_range.step );
SOAPY.current_gain_step = (int) round( (soapyGetTotalGain() - SOAPY.gain_range.minimum) / SOAPY.gain_range.step );
if (Modes.adaptive_range_target == 0)
Modes.adaptive_range_target = (SOAPY.gain_range.maximum - SOAPY.gain_range.minimum) * 0.6; // just a wild guess

Expand All @@ -369,8 +443,7 @@ bool soapyOpen(void)
// Done configuring, report the final device state
//

fprintf(stderr, "soapy: total gain: %.1fdB",
SoapySDRDevice_getGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel));
fprintf(stderr, "soapy: total gain: %.1fdB", soapyGetTotalGain());
char** gain_elements = SoapySDRDevice_listGains(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, &length);
if (gain_elements) {
for (size_t i = 0; i < length; i++) {
Expand Down Expand Up @@ -589,12 +662,12 @@ double soapyGetGainDb(int step) {
int soapySetGain(int step) {
double gainDb = soapyGetGainDb(step);

if (SoapySDRDevice_setGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, gainDb) != 0) {
if (soapySetTotalGain(gainDb) != 0) {
fprintf(stderr, "soapy: setGain(%.1fdB) failed: %s\n", gainDb, SoapySDRDevice_lastError());
return -1;
}

fprintf(stderr, "soapy: total gain set to %.1fdB", SoapySDRDevice_getGain(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel));
fprintf(stderr, "soapy: total gain set to %.1fdB", soapyGetTotalGain());
size_t length = 0;
char** gain_elements = SoapySDRDevice_listGains(SOAPY.dev, SOAPY_SDR_RX, SOAPY.channel, &length);
for (size_t i = 0; i < length; i++) {
Expand Down