working uart but not waking after sleep

semestralka_2_uart/src/sleep/shutdown.rs

@@ -0,0 +1,13 @@
+// src/sleep/standby.rs
+
+pub fn enter_shutdown() -> ! {
+    unsafe extern "C" {
+        fn HAL_PWREx_EnterSHUTDOWNMode();
+    }
+
+    unsafe {
+        HAL_PWREx_EnterSHUTDOWNMode();
+    }
+
+    cortex_m::asm::udf(); //panic
+}