gps: add GPS_{1,2}_PROTOCOL param to select protocol, default to u-blox

u-blox is the most widely used GPS, so module detection should be a bit
faster in general.

src/drivers/gps/gps.cpp

@@ -279,7 +279,25 @@ GPS::GPS(const char *path, gps_driver_mode_t mode, GPSHelper::Interface interfac
 		memset(_p_report_sat_info, 0, sizeof(*_p_report_sat_info));
 	}
 
-	_mode_auto = mode == GPS_DRIVER_MODE_NONE;
+	if (_mode == GPS_DRIVER_MODE_NONE) {
+		// use parameter to select mode if not provided via CLI
+		char protocol_param_name[16];
+		snprintf(protocol_param_name, sizeof(protocol_param_name), "GPS_%i_PROTOCOL", (int)_instance + 1);
+		int32_t protocol = 0;
+		param_get(param_find(protocol_param_name), &protocol);
+
+		switch (protocol) {
+		case 1: _mode = GPS_DRIVER_MODE_UBX; break;
+
+		case 2: _mode = GPS_DRIVER_MODE_MTK; break;
+
+		case 3: _mode = GPS_DRIVER_MODE_ASHTECH; break;
+
+		case 4: _mode = GPS_DRIVER_MODE_EMLIDREACH; break;
+		}
+	}
+
+	_mode_auto = _mode == GPS_DRIVER_MODE_NONE;
 }
 
 GPS::~GPS()

src/drivers/gps/params.c

@@ -107,3 +107,42 @@ PARAM_DEFINE_INT32(GPS_UBX_MODE, 0);
  */
 PARAM_DEFINE_FLOAT(GPS_YAW_OFFSET, 0.f);
 
+/**
+ * Protocol for Main GPS
+ *
+ * Select the GPS protocol over serial.
+ *
+ * Auto-detection will probe all protocols, and thus is a bit slower.
+ *
+ * @min 0
+ * @max 4
+ * @value 0 Auto detect
+ * @value 1 u-blox
+ * @value 2 MTK
+ * @value 3 Ashtech / Trimble
+ * @value 4 Emlid Reach
+ *
+ * @reboot_required true
+ * @group GPS
+ */
+PARAM_DEFINE_INT32(GPS_1_PROTOCOL, 1);
+
+/**
+ * Protocol for Secondary GPS
+ *
+ * Select the GPS protocol over serial.
+ *
+ * Auto-detection will probe all protocols, and thus is a bit slower.
+ *
+ * @min 0
+ * @max 4
+ * @value 0 Auto detect
+ * @value 1 u-blox
+ * @value 2 MTK
+ * @value 3 Ashtech / Trimble
+ * @value 4 Emlid Reach
+ *
+ * @reboot_required true
+ * @group GPS
+ */
+PARAM_DEFINE_INT32(GPS_2_PROTOCOL, 1);