ubx: reduce update rate for M9N to 5Hz (instead of 10Hz)

Apparently a 10Hz update rate restricts the number of used satellites to
16, and as soon as the update rate is reduced, the number of used
satellites increases.

The datasheet only mentions that the navigation rate can go up to 25Hz.

src/ubx.cpp

@@ -455,7 +455,10 @@ int GPSDriverUBX::configureDevice()
 	cfgValset<uint8_t>(UBX_CFG_KEY_ODO_OUTLPCOG, 0, cfg_valset_msg_size);
 
 	// measurement rate
-	cfgValset<uint16_t>(UBX_CFG_KEY_RATE_MEAS, 100 /* 10 Hz update rate */, cfg_valset_msg_size);
+	// In case of F9P we use 10Hz, otherwise 5Hz (receivers such as M9N can go higher as well, but
+	// the number of used satellites will be restricted to 16. Not mentioned in datasheet)
+	const int rate_meas = (_board == Board::u_blox9_F9P) ? 100 : 200;
+	cfgValset<uint16_t>(UBX_CFG_KEY_RATE_MEAS, rate_meas, cfg_valset_msg_size);
 	cfgValset<uint16_t>(UBX_CFG_KEY_RATE_NAV, 1, cfg_valset_msg_size);
 	cfgValset<uint8_t>(UBX_CFG_KEY_RATE_TIMEREF, 0, cfg_valset_msg_size);
 
@@ -1330,6 +1333,15 @@ GPSDriverUBX::payloadRxAddMonVer(const uint8_t b)
 		if (buf_index == sizeof(ubx_payload_rx_mon_ver_part2_t) - 1) {
 			// Part 2 complete: decode Part 2 buffer
 			UBX_DEBUG("VER ext \" %30s\"", _buf.payload_rx_mon_ver_part2.extension);
+
+			// in case of u-blox9 family, check if it's an F9P
+			if (_board == Board::u_blox9) {
+				if (strstr((const char *)_buf.payload_rx_mon_ver_part2.extension, "MOD=") &&
+				    strstr((const char *)_buf.payload_rx_mon_ver_part2.extension, "F9P")) {
+					_board = Board::u_blox9_F9P;
+					UBX_DEBUG("F9P detected");
+				}
+			}
 		}
 	}
 

src/ubx.h

@@ -902,7 +902,8 @@ class GPSDriverUBX : public GPSBaseStationSupport
 		u_blox6 = 6,
 		u_blox7 = 7,
 		u_blox8 = 8, ///< M8N or M8P
-		u_blox9 = 9, ///< F9P
+		u_blox9 = 9, ///< M9N, or any F9*, except F9P
+		u_blox9_F9P = 10, ///< F9P
 	};
 
 	sensor_gps_s *_gps_position {nullptr};