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gps: ask u-blox receivers only for the signals and constellations they can run #11965

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gps: ask u-blox receivers only for the signals and constellations they can run #11965

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e671436
gps: configure u-blox F10 receivers with the signals they have
MrScothh Sep 17, 2026
1e25a27
gps: never ask a u-blox receiver for more constellations than it can run
MrScothh Sep 19, 2026
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92 changes: 80 additions & 12 deletions src/main/io/gps_ublox.c
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,9 @@ static const char * baudInitDataNMEA[GPS_BAUDRATE_COUNT] = {

static ubx_nav_sig_info satelites[UBLOX_MAX_SIGNALS] = {};

// Set from the MON-VER extensions, where a dual band receiver names itself, as in FWVER=SPGL1L5
static bool ubxDualBand = false;

// MON-RF noise value (noisePerMS) reported by UBX-MON-RF as U2 at payload offset 0x10
static uint16_t monRfNoisePerMs = 0;
static uint16_t monAgcCount = 0;
Expand Down Expand Up @@ -355,6 +358,49 @@ static int configureGNSS_SBAS(ubx_gnss_element_t * gnss_block)
return 1;
}

/*
* The major constellations to ask the receiver for: the ones selected, less any it
* does not have, cut down to as many as it says it can track at once. A receiver
* refuses a configuration it cannot run and carries on with the previous one, so a
* selection that does not fit would be lost whole. When it does not fit, the
* constellations INAV leaves off by default go first. The settings are left as they
* are, and apply in full on a receiver that can take them.
*/
static uint8_t ubloxGnssToEnable(void)
{
static const uint8_t leaveOutFirst[] = {
UBX_MON_GNSS_GLONASS_MASK, UBX_MON_GNSS_BEIDOU_MASK, UBX_MON_GNSS_GALILEO_MASK
};

uint8_t gnss = UBX_MON_GNSS_GPS_MASK;
if (gpsState.gpsConfig->ubloxUseGalileo) {
gnss |= UBX_MON_GNSS_GALILEO_MASK;
}
if (gpsState.gpsConfig->ubloxUseBeidou) {
gnss |= UBX_MON_GNSS_BEIDOU_MASK;
}
if (gpsState.gpsConfig->ubloxUseGlonass) {
gnss |= UBX_MON_GNSS_GLONASS_MASK;
}

// Until MON-GNSS answers nothing is known, and the selection goes out as it is. The
// count is only trusted next to a fresh mask: it is not cleared between attempts
if (!ubx_capabilities.supported) {
return gnss;
}

gnss &= ubx_capabilities.supported;

for (unsigned i = 0; i < ARRAYLEN(leaveOutFirst); i++) {
if (ubx_capabilities.capMaxGnss <= 0 || __builtin_popcount(gnss) <= ubx_capabilities.capMaxGnss) {
break;
}
gnss &= ~leaveOutFirst[i];
}

return gnss;
}

static int configureGNSS_GALILEO(ubx_gnss_element_t * gnss_block)
{
if (!gpsUbloxHasGalileo()) {
Expand All @@ -368,7 +414,7 @@ static int configureGNSS_GALILEO(ubx_gnss_element_t * gnss_block)
// 0x10 = Galileo E5a // off by default
// 0x20 = Galileo E5b // off by default
gnss_block->sigCfgMask = 0x01;
if (gpsState.gpsConfig->ubloxUseGalileo) {
if (ubloxGnssToEnable() & UBX_MON_GNSS_GALILEO_MASK) {
gnss_block->enabled = 1;
gnss_block->resTrkCh = 4;
} else {
Expand All @@ -392,7 +438,7 @@ static int configureGNSS_BEIDOU(ubx_gnss_element_t * gnss_block)
// 0x10 = BeiDou B2I // off by default
// 0x80 = BeiDou B2A // off by default
gnss_block->sigCfgMask = 0x01;
if (gpsState.gpsConfig->ubloxUseBeidou) {
if (ubloxGnssToEnable() & UBX_MON_GNSS_BEIDOU_MASK) {
gnss_block->enabled = 1;
gnss_block->resTrkCh = 4;
} else {
Expand Down Expand Up @@ -434,7 +480,7 @@ static int configureGNSS_GLONASS(ubx_gnss_element_t * gnss_block)
// 0x01 = GLONASS L1
// 0x10 = GLONASS L2 // off by default
gnss_block->sigCfgMask = 0x01;
if (gpsState.gpsConfig->ubloxUseGlonass) {
if (ubloxGnssToEnable() & UBX_MON_GNSS_GLONASS_MASK) {
gnss_block->enabled = 1;
gnss_block->resTrkCh = 4;
} else {
Expand All @@ -447,32 +493,46 @@ static int configureGNSS_GLONASS(ubx_gnss_element_t * gnss_block)

static void configureGNSS10(void)
{
const uint8_t gnss = ubloxGnssToEnable();
const bool useGalileo = gnss & UBX_MON_GNSS_GALILEO_MASK;
const bool useBeidou = gnss & UBX_MON_GNSS_BEIDOU_MASK;
const bool useGlonass = gnss & UBX_MON_GNSS_GLONASS_MASK;

// A dual band receiver has no B1I: its Beidou L1 signal is B1C, and it rejects a
// configuration that would leave one of the two bands enabled without the other
const bool useB1C = ubxDualBand || useGlonass;

ubx_config_data8_payload_t gnssConfigValues[] = {
// SBAS
{UBLOX_CFG_SIGNAL_SBAS_ENA, gpsState.gpsConfig->sbasMode == SBAS_NONE ? 0 : 1},
{UBLOX_CFG_SIGNAL_SBAS_L1CA_ENA, gpsState.gpsConfig->sbasMode == SBAS_NONE ? 0 : 1},

// Galileo
{UBLOX_CFG_SIGNAL_GAL_ENA, gpsState.gpsConfig->ubloxUseGalileo},
{UBLOX_CFG_SIGNAL_GAL_E1_ENA, gpsState.gpsConfig->ubloxUseGalileo},
{UBLOX_CFG_SIGNAL_GAL_ENA, useGalileo},
{UBLOX_CFG_SIGNAL_GAL_E1_ENA, useGalileo},

// Beidou
// M10 can't use BDS_B1I and Glonass together. Instead, use BDS_B1C
{UBLOX_CFG_SIGNAL_BDS_ENA, gpsState.gpsConfig->ubloxUseBeidou},
{UBLOX_CFG_SIGNAL_BDS_B1_ENA, gpsState.gpsConfig->ubloxUseBeidou && ! gpsState.gpsConfig->ubloxUseGlonass},
{UBLOX_CFG_SIGNAL_BDS_B1C_ENA, gpsState.gpsConfig->ubloxUseBeidou && gpsState.gpsConfig->ubloxUseGlonass},
{UBLOX_CFG_SIGNAL_BDS_ENA, useBeidou},
{UBLOX_CFG_SIGNAL_BDS_B1_ENA, useBeidou && !useB1C},
{UBLOX_CFG_SIGNAL_BDS_B1C_ENA, useBeidou && useB1C},

// Should be enabled with GPS
{UBLOX_CFG_QZSS_ENA, 1},
{UBLOX_CFG_QZSS_L1CA_ENA, 1},
{UBLOX_CFG_QZSS_L1S_ENA, 1},

// Glonass
{UBLOX_CFG_GLO_ENA, gpsState.gpsConfig->ubloxUseGlonass},
{UBLOX_CFG_GLO_L1_ENA, gpsState.gpsConfig->ubloxUseGlonass}
// Glonass, must stay last so it can be left out
{UBLOX_CFG_GLO_ENA, useGlonass},
{UBLOX_CFG_GLO_L1_ENA, useGlonass}
};

ubloxSendSetCfgBytes(gnssConfigValues, 12);
// A receiver without Glonass has no Glonass keys either, and one unknown key makes it
// reject the whole message, taking SBAS, Galileo, BeiDou and QZSS down with it. An
// empty mask means MON-GNSS never answered and nothing is known, so send them all.
const bool noGlonass = ubx_capabilities.supported && !gpsUbloxHasGlonass();

ubloxSendSetCfgBytes(gnssConfigValues, noGlonass ? 10 : 12);
}

static void configureGNSS(void)
Expand Down Expand Up @@ -765,6 +825,13 @@ static bool gpsParseFrameUBLOX(void)
break;
}
}

for (int j = 40; j < _payload_length; j += 30) {
if (strnstr((const char *)(_buffer.bytes + j), "L1L5", 30)) {
ubxDualBand = true;
break;
}
}
}
}
break;
Expand Down Expand Up @@ -1250,6 +1317,7 @@ STATIC_PROTOTHREAD(gpsProtocolStateThread)

// Attempt to detect GPS hw version
gpsState.hwVersion = UBX_HW_VERSION_UNKNOWN;
ubxDualBand = false;
gpsState.autoConfigStep = 0;

// Configure GPS module if enabled
Expand Down
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