global: make user_input_get blocking

global.c

@@ -166,9 +166,8 @@ void sys_tick_handler(void)
 
 char user_input_get(void)
 {
-	// this is prone to error if user input is stored meanwhile (e.g. by interrupts)
-	if (!user_input_used) { // no user input available
-		return 0;
+	while (!user_input_available) { // wait for user input
+		__WFI(); // go to sleep
 	}
 	volatile char to_return = user_input_buffer[user_input_i]; // get the next available character
 	user_input_i = (user_input_i+1)%LENGTH(user_input_buffer); // update used buffer
@@ -191,9 +190,6 @@ void user_input_store(char c)
 
 bool wait_space(void)
 {
-	while (!user_input_available) { // wait for user input
-		__WFI(); // go to sleep
-	}
 	if (' '==user_input_get()) { // space entered
 		return true;
 	} else { // something else entered

global.h

@@ -419,6 +419,7 @@ void sleep_ms(uint32_t duration);
 
 /** get user input
  *  @note verify availability using user_input_available
+ *  @warning blocks and sleeps until user input is available
  *  @return user input character
  */
 char user_input_get(void);