From: Matt Mullins <mmullins@mmlx.us>
Date: Sun, 23 Dec 2012 18:10:11 +0000 (-0800)
Subject: Use LED to display the bits received from UART
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=9deb5310d58453ff42e43bad5f795dfe75dd5cdc;p=stellaris%2Fled_blink.git

Use LED to display the bits received from UART
---

diff --git a/main.c b/main.c
index 4cfd891..0aed93b 100644
--- a/main.c
+++ b/main.c
@@ -9,8 +9,13 @@ static void spin(int);
 static const int initial_systick_count = 3;
 static int systick_count;
 
+static int bit_count, blink_char;
+
 __attribute__((isr))
 void main_isr() {
+	// Initialization, since we don't blank out BSS
+	bit_count = 0;
+
 	// Power on the PLL, set to 16MHz XTAL
 	SYSCTL_RCC_R &= ~(SYSCTL_RCC_PWRDN | SYSCTL_RCC_XTAL_M);
 	SYSCTL_RCC_R |= SYSCTL_RCC_XTAL_16MHZ;
@@ -64,6 +69,12 @@ void main_isr() {
 	NVIC_ST_CURRENT_R = 0;
 	NVIC_ST_CTRL_R |= 0x7;
 
+	// Enable GPIO output for PF[3:1]
+	SYSCTL_RCGCGPIO_R |= 0x20;
+	GPIO_PORTF_DIR_R = 0xE;
+	GPIO_PORTF_DR2R_R = 0xE;
+	GPIO_PORTF_DEN_R = 0xE;
+
 	// infinite loop
 	for (;;) { 
 		asm("wfi");
@@ -82,8 +93,12 @@ __attribute__((isr))
 void uart0_isr() {
 	// Receive data, increment by 1 and send it back through the UART
 	int data = UART0_DR_R & 0xFF;
+	blink_char = data;
+
 	data = (data + 1) & 0xFF;
 	UART0_DR_R = data;
+
+	bit_count = 8;
 }
 
 __attribute__((isr))
@@ -98,4 +113,21 @@ void systick_isr() {
 
 	// Send a character out the UART for simple testing
 	UART0_DR_R = 'F';
+
+	// If we're displaying bits via the LED, bit_count keeps track of how many
+	// bits are remaining to display
+	if (bit_count) {
+		if (blink_char & 0x80) {
+			// display blue for a '1' bit
+			*(GPIO_PORTF_DATA_BITS_R + 0xE) = 0x4;
+		} else {
+			// display red for a '0' bit
+			*(GPIO_PORTF_DATA_BITS_R + 0xE) = 0x2;
+		}
+		bit_count--;
+		blink_char <<= 1;
+	} else {
+		// or if we're done, blank the LED
+		*(GPIO_PORTF_DATA_BITS_R + 0xE) = 0;
+	}
 }