--- a/Common/Inc/data_exchange.h	Tue Aug 13 13:24:54 2024 +0200
+++ b/Common/Inc/data_exchange.h	Tue Feb 11 18:12:00 2025 +0100
@@ -33,15 +33,12 @@
 
 /* Command definitions for control of external interface */
 /* 1st nibble binary on/off states */
-/* 2nd nibble UART protocol selection */
-/* 3rd nibble reserve */
-/* 4th nibble command channel */
+/* 2nd nibble target sensor ID (if sensor command is active) */
+/* 3rd nibble sensor commands */
+/* 4th nibble control channel */
 #define EXT_INTERFACE_33V_ON		(0x8000u)	/* Bit set to enable 3.3V power interface */
 #define EXT_INTERFACE_ADC_ON		(0x4000u)	/* Bit set to enable ADC conversion */
-#define EXT_INTERFACE_UART_MASK 	(0x0700u)   /* Reserve 3 bits for UART protocol selection */
-#define EXT_INTERFACE_UART_CO2  	(0x0100u)	/* Activate protocol for CO2 sensor */
-#define EXT_INTERFACE_UART_SENTINEL (0x0200u)	/* Activate Sentinel Backup monitor protocol */
-#define EXT_INTERFACE_UART_O2		(0x0400u)	/* Activate digital o2 sensor protocol (DiveO2) */
+#define EXT_INTERFACE_BUZZER_ON		(0x2000u)	/* Bit set to enable the buzzer */
 
 /* Command subset */
 #define EXT_INTERFACE_AUTODETECT 	(0x0001u)	/* Start auto detection of connected sensors	*/
@@ -57,6 +54,10 @@
 #define CO2_WARNING_LEVEL_PPM		(2000u)	    /* Early warning to indicate unexpected high co2 concentration (yellow) */
 #define CO2_ALARM_LEVEL_PPM			(5000u)		/* starting by this level CO2 has a negative impact on health (long exposure) */
 
+#define GNSS_ALIVE_STATE_ALIVE		(0x01u)		/* Communication to module active */
+#define GNSS_ALIVE_STATE_TIME		(0x02u)		/* Time information valid */
+#define GNSS_ALIVE_BACKUP_POS		(0x04u)		/* Backup position not older than x hours */
+
 enum MODE
 {
 	MODE_SURFACE	= 0,
@@ -202,6 +203,7 @@
 		//debug
 		uint32_t pressure_uTick;
 		uint32_t compass_uTick;
+		SGnssInfo gnssInfo;
 
 } 	SExchangeData;