From d21eb97de4ce14506a08765b21ae681f29a46d45 Mon Sep 17 00:00:00 2001
From: "David A. Mellis" <d.mellis@arduino.cc>
Date: Wed, 29 Nov 2006 19:35:43 +0000
Subject: [PATCH] Adding some comments to explain the interrupts.

---
 targets/arduino/WInterrupts.c | 7 +++++++
 targets/arduino/wiring.c      | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/targets/arduino/WInterrupts.c b/targets/arduino/WInterrupts.c
index 8b44bed2e..87dc25e6a 100755
--- a/targets/arduino/WInterrupts.c
+++ b/targets/arduino/WInterrupts.c
@@ -41,7 +41,13 @@ void attachInterrupt(uint8_t interruptNum, void (*userFunc)(void), int mode) {
     intFunc[interruptNum] = userFunc;
     
     if (interruptNum == 0) {
+      // Configure the interrupt mode (trigger on low input, any change, rising
+      // edge, or falling edge).  The mode constants were chosen to correspond
+      // to the configuration bits in the hardware register, so we simply shift
+      // the mode into place.
       MCUCR = (MCUCR & ~((1 << ISC00) | (1 << ISC01))) | (mode << ISC00);
+      
+      // Enable the interrupt.
       GICR |= (1 << INT0);
     } else {
       MCUCR = (MCUCR & ~((1 << ISC10) | (1 << ISC11))) | (mode << ISC10);
@@ -53,6 +59,7 @@ void attachInterrupt(uint8_t interruptNum, void (*userFunc)(void), int mode) {
 void detachInterrupt(uint8_t interruptNum) {
   if(interruptNum < EXTERNAL_NUM_INTERRUPTS) {
     if (interruptNum == 0)
+      // Disable the interrupt.
       GICR &= ~(1 << INT0);
     else
       GICR &= ~(1 << INT1);
diff --git a/targets/arduino/wiring.c b/targets/arduino/wiring.c
index 9890c5b09..b3444cbd9 100755
--- a/targets/arduino/wiring.c
+++ b/targets/arduino/wiring.c
@@ -41,7 +41,7 @@
 // Define constants and variables for buffering incoming serial data.  We're
 // using a ring buffer (I think), in which rx_buffer_head is the index of the
 // location to which to write the next incoming character and rx_buffer_tail
-// is the index of the location from which to read
+// is the index of the location from which to read.
 #define RX_BUFFER_SIZE 128
 
 unsigned char rx_buffer[RX_BUFFER_SIZE];