diff --git a/src/main.c b/src/main.c
--- a/src/main.c
+++ b/src/main.c
@@ -12,27 +12,45 @@
 #include "gpio.h"
 #include "gps.h"
 
-
-void sysclk_init(void);
-
 #define WSPR_DEFAULT_FREQ 10140100UL
 #define WSPR_TONE_SPACING 146 // ~1.46 Hz
 #define WSPR_CTC 10672 // CTC value for WSPR
 
+// Private functions
+void sysclk_init(void);
+void enter_sleep(void);
+void enter_deepsleep(void);
+
+// Test stuff
 char call[7] = "KD8TDF";
 char loc[5] = "EN72";
 uint8_t dbm = 10;
 uint8_t tx_buffer[255];
 
-
+// Frequencies and channel info
 uint32_t freq = WSPR_DEFAULT_FREQ;
 uint8_t symbol_count = WSPR_SYMBOL_COUNT;
 uint16_t ctc = WSPR_CTC;
 uint16_t tone_spacing = WSPR_TONE_SPACING;
 volatile uint8_t proceed = 0;
 
+// Bring up TCXO and oscillator IC
 void encode_wspr(void)
 {
+    HAL_GPIO_WritePin(OSC_NOTEN, 0);
+    HAL_GPIO_WritePin(TCXO_EN, 1);
+    HAL_Delay(100);
+
+    // Bring up the chip
+    si5351_init(i2c_get(), SI5351_CRYSTAL_LOAD_8PF, 0);
+    si5351_set_correction(0);
+    //si5351_set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
+    //si5351_set_ms_source(SI5351_CLK0, SI5351_PLLA);
+    si5351_set_freq(WSPR_DEFAULT_FREQ * 100, 0, SI5351_CLK0);
+    si5351_drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA); // Set for max power if desired (8ma max)
+    si5351_output_enable(SI5351_CLK0, 1);
+    //si5351_pll_reset(SI5351_PLLA);
+
     // Encode message to transmit
     wspr_encode(call, loc, dbm, tx_buffer);
 
@@ -53,8 +71,12 @@ void encode_wspr(void)
 
     // Disable transmitter
     si5351_output_enable(SI5351_CLK0, 0);
+
+    HAL_GPIO_WritePin(OSC_NOTEN, 1);
+    HAL_GPIO_WritePin(TCXO_EN, 0);
 }
 
+
 TIM_HandleTypeDef htim1;
 
 int main(void)
@@ -67,8 +89,9 @@ int main(void)
     adc_init();
     i2c_init();
 
-    HAL_GPIO_WritePin(OSC_NOTEN, 0);
-    HAL_GPIO_WritePin(TCXO_EN, 1);
+    // Disable ICs
+    HAL_GPIO_WritePin(OSC_NOTEN, 1);
+    HAL_GPIO_WritePin(TCXO_EN, 0);
 
 
     // Start timer for WSPR
@@ -91,19 +114,21 @@ int main(void)
 
     jtencode_init();
     //gps_init();
-    si5351_init(i2c_get(), SI5351_CRYSTAL_LOAD_8PF, 0);
-    si5351_set_correction(0);
-    //si5351_set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
-    //si5351_set_ms_source(SI5351_CLK0, SI5351_PLLA);
-    si5351_set_freq(WSPR_DEFAULT_FREQ * 100, 0, SI5351_CLK0);
-    si5351_drive_strength(SI5351_CLK0, SI5351_DRIVE_2MA); // Set for max power if desired (8ma max)
-    si5351_output_enable(SI5351_CLK0, 1);
-    //si5351_pll_reset(SI5351_PLLA);
 
     uint32_t led_timer = HAL_GetTick();
     uint32_t last_gps  = HAL_GetTick();
     uint32_t last_wspr  = 0xfffff; // start immediately. 
 
+    HAL_GPIO_TogglePin(LED_BLUE);
+    HAL_Delay(100);
+    HAL_GPIO_TogglePin(LED_BLUE);
+    HAL_Delay(100);
+    HAL_GPIO_TogglePin(LED_BLUE);
+    HAL_Delay(100);
+    HAL_GPIO_TogglePin(LED_BLUE);
+    HAL_Delay(100);
+
+
     while (1)
     {
         if(HAL_GetTick() - last_wspr > 120000)
@@ -117,15 +142,37 @@ int main(void)
             HAL_GPIO_TogglePin(LED_BLUE);
             led_timer = HAL_GetTick();
         }
-        if(HAL_GetTick() - last_gps > 100)
+        if(HAL_GetTick() - last_gps > 3000)
         {
 //            gps_process();
             last_gps = HAL_GetTick();
         }
+
+        enter_sleep();
     }
+
 }
 
 
+void enter_sleep(void)
+{
+    //HAL_SuspendTick();
+    HAL_TIM_Base_Stop_IT(&htim1);
+    HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_SLEEPENTRY_WFI);
+    HAL_TIM_Base_Start_IT(&htim1);
+    //HAL_ResumeTick();
+}
+
+void enter_deepsleep(void) 
+{
+    // Request to enter STOP mode with regulator in low power mode
+    HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
+    // After wake-up from STOP reconfigure the PLL
+    sysclk_init();
+}
+
+
+
 // Initialize system clocks
 void sysclk_init(void)
 {