global: add central user input storage

global.c

@@ -35,6 +35,11 @@
 
 volatile bool button_flag = false;
 volatile uint32_t sleep_duration = 0; /**< sleep duration count down (in SysTick interrupts) */
+volatile bool user_input_available = false;
+
+static volatile uint8_t user_input_buffer[64] = {0}; /**< ring buffer for received data */
+static volatile uint8_t user_input_i = 0; /**< current position of read received data */
+static volatile uint8_t user_input_used = 0; /**< how much data has been received and not red */
 
 char* b2s(uint64_t binary, uint8_t rjust)
 {
@@ -159,6 +164,44 @@ 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;
+	}
+	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
+	user_input_used--; // update used buffer
+	user_input_available = (user_input_used!=0); // update available data
+	return to_return;
+}
+
+void user_input_store(char c)
+{
+	// only save data if there is space in the buffer
+	if (user_input_used>=LENGTH(user_input_buffer)) { // if buffer is full
+		user_input_i = (user_input_i+1)%LENGTH(user_input_buffer); // drop oldest data
+		user_input_used--; // update used buffer information
+	}
+	user_input_buffer[(user_input_i+user_input_used)%LENGTH(user_input_buffer)] = c; // put character in buffer
+	user_input_used++; // update used buffer
+	user_input_available = true; // update available data
+}
+
+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
+		return false;
+	}
+}
+
+
 void board_setup(void)
 {
 	// setup LED
@@ -193,6 +236,11 @@ void board_setup(void)
 	exti_enable_request(EXTI(BUTTON_PIN)); // enable external interrupt
 	nvic_enable_irq(NVIC_EXTI_IRQ(BUTTON_PIN)); // enable interrupt
 #endif
+
+	// reset user input buffer
+	user_input_available = false;
+	user_input_i = 0;
+	user_input_used = 0;
 }
 
 #if defined(BUTTON_PIN)

global.h

@@ -378,8 +378,10 @@ extern uint32_t __application_beginning;
  *  @note this symbol will be provided by the linker script
  */
 extern uint32_t __application_end;
-
-extern volatile bool button_flag; /**< flag set when board user button has been pressed/released */
+/** flag set when board user button has been pressed/released */
+extern volatile bool button_flag;
+/** flag set when user input is available */
+extern volatile bool user_input_available;
 
 /** get binary representation of a number
  *  @param[in] binary number to represent in binary
@@ -415,8 +417,19 @@ void sleep_us(uint32_t duration);
  */
 void sleep_ms(uint32_t duration);
 
+/** get user input
+ *  @note verify availability using user_input_available
+ *  @return user input character
+ */
+char user_input_get(void);
+
+/** store user input
+ *  @param[in] c user input character to store
+ *  @note old data will be overwritten when buffer is full
+ */
+void user_input_store(char c);
+
 /** wait for user to press space
- *  @note needs to be implemented by the main application depending on the user inputs
  *  @return if the user press space (true) or something else
  */
 bool wait_space(void);