From 55cb2009d9a9f71a606ff4b6c871e854dce7bb9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Sun, 17 Jan 2016 15:03:10 +0100
Subject: [PATCH] example now echos back UART communication

---
 lib/usart.c |  7 +++----
 lib/usart.h |  2 +-
 main.c      | 20 +++++++++-----------
 3 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/lib/usart.c b/lib/usart.c
index f1fb42d..4c862a8 100644
--- a/lib/usart.c
+++ b/lib/usart.c
@@ -13,9 +13,7 @@
  *
  */
 /* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
-/* this library handles the USART
- * it uses the TX and RX pins (depending on which USART is used)
- */
+/* this library handles the USART */
 
 /* standard libraries */
 #include <stdint.h> // standard integer types
@@ -55,7 +53,8 @@ void usart_setup(void)
 	usart_set_parity(USART, USART_PARITY_NONE);
 	usart_set_flow_control(USART, USART_FLOWCONTROL_NONE);
 
-	nvic_enable_irq(USART_IRQ); // enable the USART2 interrupt
+	nvic_enable_irq(USART_IRQ); // enable the USART interrupt
+	usart_enable_rx_interrupt(USART); // enable receive interrupt
 	usart_enable(USART); // enable USART
 
 	/* reset buffer states */
diff --git a/lib/usart.h b/lib/usart.h
index 22933a4..0fd167e 100644
--- a/lib/usart.h
+++ b/lib/usart.h
@@ -13,7 +13,7 @@
  *
  */
 /* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
-/* This library handles the USART */
+/* this library handles the USART */
 
 /* which USART to use */
 #define USART USART1
diff --git a/main.c b/main.c
index 45da4fe..eeaa246 100644
--- a/main.c
+++ b/main.c
@@ -61,24 +61,22 @@ static void gpio_setup(void)
 }
 
 int main(void)
-{
-	int i, c = 0;
-	
+{	
 	SCB_VTOR = (uint32_t) 0x08002000; // relocate vector table because of the bootloader
 
-	clock_setup();
-	gpio_setup();
-	usart_setup();
+	clock_setup(); // setup main clock
+	gpio_setup(); // setup main inputs/ouputs
+	usart_setup(); // setup USART (for printing)
 	setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print	
 	setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
 
 	/* blink the LED with every transmitted character */
 	while (1) {
-		gpio_toggle(LED_PORT, LED_PIN);	/* LED on/off */
-		printf("%c",c+'0');
-		c = (c == 9) ? 0 : c + 1;	/* increment c */
-		for (i = 0; i < 8000000; i++)	/* wait a bit */
-			__asm__("nop");
+		while (usart_received) { // echo every received character
+			gpio_toggle(LED_PORT, LED_PIN);	// toggle LED
+			printf("%c",usart_getchar()); // transmit receive character
+		}
+		__asm__("wfi"); // go to sleep
 	}
 
 	return 0;