diff --git a/firmware/inc/gps.h b/firmware/inc/gps.h
index 2c70a2d..1ade0d0 100644
--- a/firmware/inc/gps.h
+++ b/firmware/inc/gps.h
@@ -33,8 +33,10 @@ enum gps_error_t {
   GPS_ERROR_INVALID_FRAME,
 };
 
-void gps_update(void);
-void gps_update_wait(void);
+void gps_update_time(void);
+void gps_update_position(void);
+int gps_update_time_pending(void);
+int gps_update_position_pending(void);
 
 struct ubx_nav_posllh gps_get_nav_posllh();
 struct ubx_nav_sol gps_get_nav_sol();
diff --git a/firmware/inc/rtty.h b/firmware/inc/rtty.h
index 600e323..5088927 100644
--- a/firmware/inc/rtty.h
+++ b/firmware/inc/rtty.h
@@ -25,8 +25,21 @@
 #ifndef RTTY_H
 #define RTTY_H
 
+#include "util/dbuffer.h"
+
+/**
+ * Output String
+ */
+#define RTTY_STRING_MAX	0x200
+/**
+ * It's actually a double buffer which we swap for mid-string updates
+ */
+ARRAY_DBUFFER_T(char, RTTY_STRING_MAX) rtty_dbuffer_string;
+
 int rtty_active(void);
-int rtty_set_string(char* string, uint32_t length);
+int rtty_start(void);
+int32_t rtty_get_index(void);
+void rtty_set_length(int32_t length);
 void rtty_tick(void);
 
 #endif /* RTTY_H */
diff --git a/firmware/inc/telemetry.h b/firmware/inc/telemetry.h
index 743c57d..27f3287 100644
--- a/firmware/inc/telemetry.h
+++ b/firmware/inc/telemetry.h
@@ -25,6 +25,6 @@
 #ifndef TELEMETRY_H
 #define TELEMETRY_H
 
-void set_telemetry_string(void);
+uint16_t crc_checksum(char *string);
 
 #endif /* TELEMETRY_H */
diff --git a/firmware/src/gps.c b/firmware/src/gps.c
index b51d08b..6f62760 100644
--- a/firmware/src/gps.c
+++ b/firmware/src/gps.c
@@ -281,24 +281,37 @@ void gps_disable_nmea(void)
 }
 
 /**
- * Sends messages to the GPS to update the fields we want
+ * Sends messages to the GPS to update the time
  */
-void gps_update(void)
+void gps_update_time(void)
+{
+  _ubx_send_message((ubx_message_t*)&ubx_nav_timeutc, NULL, 0);
+};
+/**
+ * Sends messages to the GPS to update the position
+ */
+void gps_update_position(void)
 {
   _ubx_send_message((ubx_message_t*)&ubx_nav_posllh, NULL, 0);
   _ubx_send_message((ubx_message_t*)&ubx_nav_sol, NULL, 0);
-  _ubx_send_message((ubx_message_t*)&ubx_nav_timeutc, NULL, 0);
-  _ubx_send_message((ubx_message_t*)&ubx_nav_status, NULL, 0);
+
+  // _ubx_send_message((ubx_message_t*)&ubx_nav_status, NULL, 0);
 }
 /**
- * Waits for any pending updates from the GPS
+ * Indicates a pending time update from the GPS
  */
-void gps_update_wait(void)
+int gps_update_time_pending(void)
 {
-  while (ubx_nav_posllh.state == UBX_PACKET_WAITING);
-  while (ubx_nav_sol.state == UBX_PACKET_WAITING);
-  while (ubx_nav_timeutc.state == UBX_PACKET_WAITING);
-  while (ubx_nav_status.state == UBX_PACKET_WAITING);
+  return (ubx_nav_timeutc.state == UBX_PACKET_WAITING);
+}
+/**
+ * Indicates a pending position update from the GPS
+ */
+int gps_update_position_pending(void)
+{
+  return (ubx_nav_posllh.state == UBX_PACKET_WAITING) ||
+    (ubx_nav_sol.state == UBX_PACKET_WAITING);
+  //(ubx_nav_status.state == UBX_PACKET_WAITING);
 }
 /**
  * Return the latest received messages
diff --git a/firmware/src/main.c b/firmware/src/main.c
index 1290081..d25f2ca 100644
--- a/firmware/src/main.c
+++ b/firmware/src/main.c
@@ -34,15 +34,19 @@
 #include "system/port.h"
 #include "tc/tc_driver.h"
 #include "gps.h"
+#include "ubx_messages.h"
 #include "system/wdt.h"
 #include "timepulse.h"
 #include "telemetry.h"
 //#include "si406x.h"
+#include "analogue.h"
 #include "si4060.h"
 #include "spi_bitbang.h"
 #include "rtty.h"
 #include "system/interrupt.h"
 
+#define CALLSIGN	"UBSEDSx"
+
 void si4060_hw_init(void)
 {
   /* Configure the SDN pin */
@@ -177,6 +181,129 @@ void powermananger_init(void)
 			      PM_APBAMASK_RTC); /* RTC is unused */
 }
 
+
+/**
+ * Telemetry String
+ * =============================================================================
+ */
+void output_telemetry_string(void)
+{
+  double lat_fmt = 0.0;
+  double lon_fmt = 0.0;
+  uint32_t altitude = 0;
+
+  /**
+   * Callsign, Time
+   * ---------------------------------------------------------------------------
+   */
+
+  /* GPS Time */
+  gps_update_time();
+
+  /* Sleep Wait */
+  while (gps_update_time_pending()) {
+    system_sleep();
+  }
+  for (int i = 0; i < 100*1000; i++);
+
+  /* Time */
+  struct ubx_nav_timeutc time = gps_get_nav_timeutc();
+  uint8_t hours = time.payload.hour;
+  uint8_t minutes = time.payload.min;
+  uint8_t seconds = time.payload.sec;
+
+  /* init double buffers */
+  ARRAY_DBUFFER_INIT(&rtty_dbuffer_string);
+
+  /* sprintf - initial string */
+  uint16_t len = sprintf(ARRAY_DBUFFER_WRITE_PTR(&rtty_dbuffer_string),
+			 "$$UBSEDSx,%02u:%02u:%02u,",
+			 hours, minutes, seconds);
+
+  /* swap buffers */
+  ARRAY_DBUFFER_SWAP(&rtty_dbuffer_string);
+
+  /* start */
+  rtty_start();
+
+  /**
+   * Position, Status, Analogue, Checksum
+   * ---------------------------------------------------------------------------
+   */
+
+  /* Analogue */
+  float battery = get_battery();
+  float temperature = si4060_get_temperature();
+
+  /* Sleep Wait */
+  while (rtty_get_index() < (len - 4)) {
+    system_sleep();
+  }
+
+  /* Request updates from the gps */
+  gps_update_position();
+  if (gps_is_locked()) {
+    led_on();
+  } else {
+    led_off();
+  }
+
+  /* Wait for the gps update. Move on if it's urgent */
+  while (gps_update_position_pending() && rtty_get_index() < (len - 1)) {
+    system_sleep();
+  }
+
+  if (gps_is_locked()) {
+    led_off();
+  } else {
+    led_on();
+  }
+
+  /* GPS Status */
+  struct ubx_nav_sol sol = gps_get_nav_sol();
+  uint8_t lock = sol.payload.gpsFix;
+  uint8_t satillite_count = sol.payload.numSV;
+
+  /* GPS Position */
+  if (lock == 0x2 || lock == 0x3 || lock == 0x4) {
+    struct ubx_nav_posllh pos = gps_get_nav_posllh();
+    lat_fmt = (double)pos.payload.lat / 10000000.0;
+    lon_fmt = (double)pos.payload.lon / 10000000.0;
+    altitude = pos.payload.height / 1000;
+  }
+
+  /* sprintf - full string */
+  len = sprintf(ARRAY_DBUFFER_WRITE_PTR(&rtty_dbuffer_string),
+		 "$$UBSEDSx,%02u:%02u:%02u,%02.6f,%03.6f,%ld,%u,%.2f,%.1f",
+		 hours, minutes, seconds, lat_fmt, lon_fmt, altitude,
+		 satillite_count, battery, temperature);
+
+  /* sprintf - checksum */
+  len += sprintf(ARRAY_DBUFFER_WRITE_PTR(&rtty_dbuffer_string) + len,
+		 "*%04X\n",
+		 crc_checksum(ARRAY_DBUFFER_WRITE_PTR(&rtty_dbuffer_string)));
+
+  /* swap buffers */
+  ARRAY_DBUFFER_SWAP(&rtty_dbuffer_string);
+
+  /**
+   * End
+   * ---------------------------------------------------------------------------
+   */
+
+  /* Set the final length */
+  rtty_set_length(len);
+
+  /* Sleep Wait */
+  while (rtty_active()) {
+    system_sleep();
+  }
+}
+
+/**
+ * MAIN
+ * =============================================================================
+ */
 int main(void)
 {
   /**
@@ -200,7 +327,7 @@ int main(void)
 
   /* Configure Sleep Mode */
   system_set_sleepmode(SYSTEM_SLEEPMODE_STANDBY);
-  system_set_sleepmode(SYSTEM_SLEEPMODE_IDLE_1); /* Disable CPU, AHB. APB still runs */
+  system_set_sleepmode(SYSTEM_SLEEPMODE_IDLE_0); /* Disable CPU, AHB. APB still runs */
 
   /* Configure the Power Manager */
   powermananger_init();
@@ -239,36 +366,11 @@ int main(void)
   si4060_start_tx(0);
 
   while (1) {
-    /* Send the last packet */
-    while (rtty_active());
-
-    port_pin_set_output_level(SI406X_GPIO0_PIN, 0);
-
     /* Watchdog */
     wdt_reset_count();
 
-    gps_update();		/* Request updates from the gps */
-
-    if (gps_is_locked()) {
-      led_on();
-    } else {
-      led_off();
-    }
-
-    gps_update_wait();		/* Wait for the gps update */
-
-    if (gps_is_locked()) {
-      led_off();
-    } else {
-      led_on();
-    }
-
     /* Set the next packet */
-    set_telemetry_string();
-
-    port_pin_set_output_level(SI406X_GPIO0_PIN, 1);
-
-    system_sleep();
+    output_telemetry_string();
   }
 }
 
diff --git a/firmware/src/rtty.c b/firmware/src/rtty.c
index 5d88845..1e42b4c 100644
--- a/firmware/src/rtty.c
+++ b/firmware/src/rtty.c
@@ -25,6 +25,7 @@
 #include <string.h>
 
 #include "samd20.h"
+#include "rtty.h"
 #include "hw_config.h"
 #include "system/port.h"
 
@@ -42,11 +43,6 @@
 #define ASCII_BITS	8
 #define BITS_PER_CHAR	11
 
-/**
- * Output String
- */
-#define RTTY_STRING_MAX	0x200
-
 /**
  * Where we currently are in the rtty output byte
  *
@@ -59,13 +55,12 @@ uint8_t rtty_phase;
 /**
  * Where we are in the current output string
  */
-uint32_t rtty_index;
+int32_t rtty_index;
 
 /**
  * Details of the string that is currently being output
  */
-char rtty_string[RTTY_STRING_MAX];
-uint32_t rtty_string_length = 0;
+int32_t rtty_string_length = 0;
 
 /**
  * Returns 1 if we're currently outputting.
@@ -75,25 +70,35 @@ int rtty_active(void) {
 }
 
 /**
- * Sets an output string.
+ * Starts RTTY output
  *
- * Returns 0 on success, 1 if a string is already active or 2 if the
- * specified string was too long.
+ * Returns 0 on success, 1 if already active
  */
-int rtty_set_string(char* string, uint32_t length) {
-  if (length > RTTY_STRING_MAX) return 2; // To long
-
+int rtty_start(void) {
   if (!rtty_active()) {
-    // Copy
-    memcpy(rtty_string, string, length);
-    rtty_string_length = length;
-    // Initialise
+
+    /* Initialise */
+    rtty_string_length = RTTY_STRING_MAX;
     rtty_index = 0;
     rtty_phase = 0;
 
-    return 0; // Success
+    return 0; /* Success */
   } else {
-    return 1; // Already active
+    return 1; /* Already active */
+  }
+}
+/**
+ * Returns the index of the current byte being outputted from the buffer
+ */
+int32_t rtty_get_index(void) {
+  return rtty_index;
+}
+/**
+ * Sets the final length of the RTTY string
+ */
+void rtty_set_length(int32_t length) {
+  if (length <= RTTY_STRING_MAX) {
+    rtty_string_length = length;
   }
 }
 
@@ -110,7 +115,7 @@ void rtty_tick(void) {
       port_pin_set_output_level(SI406X_GPIO1_PIN, 1);
     } else if (rtty_phase < ASCII_BITS + 1) {
       // Data
-      if ((rtty_string[rtty_index] >> (rtty_phase - 1)) & 1) {
+      if ((ARRAY_DBUFFER_READ_PTR(&rtty_dbuffer_string)[rtty_index] >> (rtty_phase - 1)) & 1) {
 	//RTTY_SET(1);
 	port_pin_set_output_level(SI406X_GPIO1_PIN, 0);
       } else {
diff --git a/firmware/src/telemetry.c b/firmware/src/telemetry.c
index 4b7e242..189843a 100644
--- a/firmware/src/telemetry.c
+++ b/firmware/src/telemetry.c
@@ -26,16 +26,6 @@
 #include <string.h>
 
 #include "samd20.h"
-#include "semihosting.h"
-#include "analogue.h"
-#include "gps.h"
-#include "rtty.h"
-#include "ubx_messages.h"
-#include "si4060.h"
-
-//#define SEMIHOST_LOG
-
-char telemetry_string[0x200];
 
 /**
  * CRC Function for the XMODEM protocol.
@@ -77,53 +67,3 @@ uint16_t crc_checksum(char *string)
 
   return crc;
 }
-/**
- * Sets output telemetry
- */
-void set_telemetry_string(void)
-{
-  double lat_fmt = 0.0;
-  double lon_fmt = 0.0;
-  uint32_t altitude = 0;
-
-  /* Analogue */
-  float battery = get_battery();
-  float temperature = si4060_get_temperature();
-
-  /* Time */
-  struct ubx_nav_timeutc time = gps_get_nav_timeutc();
-  uint8_t hours = time.payload.hour;
-  uint8_t minutes = time.payload.min;
-  uint8_t seconds = time.payload.sec;
-
-  /* GPS Status */
-  struct ubx_nav_sol sol = gps_get_nav_sol();
-  uint8_t lock = sol.payload.gpsFix;
-  uint8_t satillite_count = sol.payload.numSV;
-
-  /* GPS Position */
-  if (lock == 0x2 || lock == 0x3 || lock == 0x4) {
-    struct ubx_nav_posllh pos = gps_get_nav_posllh();
-    lat_fmt = (double)pos.payload.lat / 10000000.0;
-    lon_fmt = (double)pos.payload.lon / 10000000.0;
-    altitude = pos.payload.height / 1000;
-  }
-
-
-//#ifdef SEMIHOST_LOG
-//  semihost_printf("Batt %f, Temp %f\n", battery, temperature);
-//  semihost_printf("%02.7f,%03.7f,%ld\n", lat_fmt, lon_fmt, altitude);
-//  semihost_printf("Lock: %d Sats: %d\n", lock, satillite_count);
-//  semihost_printf("%02u:%02u:%02u\n", hours, minutes, seconds);
-//#endif
-
-  /* sprintf */
-  uint16_t len = sprintf(telemetry_string,
-			 "$$UBSEDSx,%02u:%02u:%02u,%02.6f,%03.6f,%ld,%u,%.2f,%.1f",
-			 hours, minutes, seconds, lat_fmt, lon_fmt, altitude,
-			 satillite_count, battery, temperature);
-
-  sprintf(telemetry_string + len, "*%04X\n", crc_checksum(telemetry_string));
-
-  rtty_set_string(telemetry_string, strlen(telemetry_string));
-}