main: sleep instead of busy-loop

src/main.c

@@ -45,6 +45,9 @@ int main()
     TMR0_ITCfg(ENABLE, TMR0_3_IT_CYC_END);
     PFIC_EnableIRQ(TMR0_IRQn);
 
+    TMR1_TimerInit((FREQ_SYS / 1000));
+    TMR1_ITCfg(ENABLE, TMR0_3_IT_CYC_END);
+
     TMR3_TimerInit(FREQ_SYS / 200);
     TMR3_ITCfg(ENABLE, TMR0_3_IT_CYC_END);
     PFIC_EnableIRQ(TMR3_IRQn);
@@ -58,6 +61,9 @@ int main()
 
     screen_push(&badge_screen);
 
+    // set SEVONPEND
+    PFIC->SCTLR |= (1 << 4);
+
     while (1) {
         WWDG_SetCounter(0x7F);
         static int btldr_timer = 0;
@@ -108,6 +114,11 @@ int main()
         TMOS_SystemProcess();
         cdc_tick();
         hid_tick();
-        DelayMs(1);
+
+        while (!TMR1_GetITFlag(TMR0_3_IT_CYC_END)) {
+            __SEV();
+            __asm__ volatile("wfi");
+        }
+        TMR1_ClearITFlag(TMR0_3_IT_CYC_END);
     }
 }