diff --git a/src/main.c b/src/main.c
--- a/src/main.c
+++ b/src/main.c
@@ -17,6 +17,13 @@
 // Probabl wake up 1 minute early -- 0.45min possible +/- on wakeup time with 15min sync intervals
 
 
+// TODO: Add JT9 message with more grid locator digits + altitude + vbatt + temp
+// MSG13charmax:
+// 	X: gridloc
+//  Y: altitude
+//  Z: temperature
+//  KD8TDF XXYYZZ // could use alt callsign thing
+
 enum _state
 {
     SYSTEM_IDLE = 0, // awaiting RTC interrupt for wakeup TODO wake up before scheduled time to get fix?
@@ -98,17 +105,22 @@ int main(void)
             case SYSTEM_IDLE:
             {
                 blink_rate = BLINK_SLOW;
-                HAL_PWR_EnterSLEEPMode(0, PWR_SLEEPENTRY_WFI);
-                HAL_PWR_EnterSLEEPMode(0, PWR_SLEEPENTRY_WFI);
-                HAL_PWR_EnterSLEEPMode(0, PWR_SLEEPENTRY_WFI);
+
+                // Actually sleep for real: disable systick and sleep until RTC interrupt
+                HAL_SuspendTick();
+
+                // Enter sleep mode: wait for interrupt
                 HAL_PWR_EnterSLEEPMode(0, PWR_SLEEPENTRY_WFI);
 
-                // Wait for RTC wakeup interrupt
-                //wfi();
-                //enter_sleep();
+                // We have woken up!
+
+                // This is hopefully the only timer that needs to stay alive in idle mode
+                last_wspr_tx_time += 0; // move this timer forward based on sleep length
 
-                // Somehow go to another state when we get an interrupt
-//                state = SYSTEM_GPSACQ;
+                HAL_ResumeTick();
+
+                // TODO: Eventually use GPS time to calibrate the RTC maybe
+
             } break;