Add support for fixing GPS_BAUDRATE

If GPS_BAUDRATE is set in variant.h, the deployer knows something we
don't about the GPS. Used especially when the GPS is soldered to a board
in a commercial product :) If we see that, we don't try other baud rates
at all.

src/configuration.h

@@ -207,6 +207,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #ifndef GPS_BAUDRATE
 #define GPS_BAUDRATE 9600
+#define GPS_BAUDRATE_FIXED 0
+#else
+#define GPS_BAUDRATE_FIXED 1
 #endif
 
 /* Step #2: follow with defines common to the architecture;

src/gps/GPS.cpp

@@ -413,6 +413,13 @@ int GPS::getACK(uint8_t *buffer, uint16_t size, uint8_t requestedClass, uint8_t
     return 0;
 }
 
+/**
+ * @brief  Setup the GPS based on the model detected.
+ *  We detect the GPS by cyling through a set of baud rates, first common then rare.
+ *  For each baud rate, we run GPS::Probe to send commands and match the responses
+ *  to known GPS responses.
+ * @retval Whether setup reached the end of its potential to configure the GPS.
+ */
 bool GPS::setup()
 {
 
@@ -420,14 +427,17 @@ bool GPS::setup()
         int msglen = 0;
         if (tx_gpio && gnssModel == GNSS_MODEL_UNKNOWN) {
 
-            // if GPS_BAUDRATE is specified in variant (i.e. not 9600), skip to the specified rate.
+            // if GPS_BAUDRATE is specified in variant, skip to the specified rate.
-            if (probeTries == 0 && speedSelect == 0 && GPS_BAUDRATE != serialSpeeds[speedSelect]) {
+            if (GPS_BAUDRATE_FIXED) {
-                speedSelect = std::find(serialSpeeds, std::end(serialSpeeds), GPS_BAUDRATE) - serialSpeeds;
+                gnssModel = probe(GPS_BAUDRATE);
-                if (speedSelect == 0) {
+                if (gnssModel == GNSS_MODEL_UNKNOWN && probeTries == 1) {
-                    speedSelect = std::find(rareSerialSpeeds, std::end(rareSerialSpeeds), GPS_BAUDRATE) - rareSerialSpeeds;
+                    LOG_WARN("GPS probe failed, setting to %d", GPS_BAUDRATE);
-                    probeTries = 1;
+                    return true;
-                }
+                } else {
+                    ++probeTries;
+                    return false;
                 }
+            } else {
                 if (probeTries == 0) {
                     LOG_DEBUG("Probing for GPS at %d", serialSpeeds[speedSelect]);
                     gnssModel = probe(serialSpeeds[speedSelect]);
@@ -447,9 +457,10 @@ bool GPS::setup()
                             LOG_WARN("Giving up on GPS probe and setting to %d", GPS_BAUDRATE);
                             return true;
                         }
-                    return false;
                     }
                 }
+                return false;
+            }
         } else {
             gnssModel = GNSS_MODEL_UNKNOWN;
         }

src/gps/GPS.h

@@ -76,9 +76,8 @@ class GPS : private concurrency::OSThread
     uint8_t fixType = 0;      // fix type from GPGSA
 #endif
   private:
-
+    const int serialSpeeds[3] = {9600, 115200, 38400};
-    const int serialSpeeds[6] = {9600, 115200, 38400};
+    const int rareSerialSpeeds[3] = {4800, 57600, GPS_BAUDRATE};
-    const int rareSerialSpeeds[6] = {4800, 57600, GPS_BAUDRATE};
 
     uint32_t lastWakeStartMsec = 0, lastSleepStartMsec = 0, lastFixStartMsec = 0;
     uint32_t rx_gpio = 0;