From f33c949d3ce62846ffef9483e7f61bbeba188b87 Mon Sep 17 00:00:00 2001
From: BinHong Lee <binhong@binhong.me>
Date: Mon, 17 Apr 2017 02:02:22 -0700
Subject: [PATCH] Code commented

---
 main.c | 82 +++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 61 insertions(+), 21 deletions(-)

diff --git a/main.c b/main.c
index f5582b3..413deb7 100644
--- a/main.c
+++ b/main.c
@@ -3,100 +3,140 @@
 #include <stdint.h>
 #include <wiringPi.h>
 #include <wiringPiI2C.h>
-#include <errno.h>
 
+//Preset information about MPU3050 (gyro sensor)
 #define MPU3050_PWR	(0x6b)
 #define MPU3050_I2C	(0x69)
 #define MPU3050_REG	(0x21)
-#define	LED	0
+
+//Preset buzzer WiringPi port
+#define	BUZZER	0
+
+//Preset button interrupt WiringPi port
 #define BUTTON	5
+//Preset button debounce time
 #define DEBOUNCE_MS	1000
 
-volatile int trigger;
+//Declaring all global variables
+volatile uint8_t trigger;
 volatile uint8_t photoTaken;
 volatile unsigned int prevTime = 0;
 volatile uint8_t btnClicked = 0;
 
-void myInterrupt(void)
+void buttonInterrupt()
 {
+	//Get the current time and its difference from last interrupt
 	unsigned int currentTime = millis();
 	unsigned int deltaTime = currentTime - prevTime;
 
-	printf("%d\n", deltaTime);
+	//Check if the deltaTime from the last click is longer than the preset debounce time
 	if (deltaTime > DEBOUNCE_MS)
 	{
+		//Set new values
 		btnClicked = 1;
 		prevTime = currentTime;
-		printf("test\n");
+
 		if (trigger == 0)
 		{
-			photoTaken = 0;
+			//Set trigger and turn off buzzer
 			trigger = 1;
-			digitalWrite(LED, LOW);
-			printf("T R I G G E R R E D\n");
+			digitalWrite(BUZZER, LOW);
 		}
 		else
 		{
+			//Reset photoTaken and trigger
 			photoTaken = 0;
 			trigger = 0;
-			digitalWrite(LED, HIGH);
+
+			//Double short beep to inform rider
+			digitalWrite(BUZZER, HIGH);
 			delay(100);
-			digitalWrite(LED, LOW);
+			digitalWrite(BUZZER, LOW);
 			delay(100);
-			digitalWrite(LED, HIGH);
+			digitalWrite(BUZZER, HIGH);
 			delay(100);
-			digitalWrite(LED, LOW);
-			printf("T R I G G E R R E D  A G A I N\n");
+			digitalWrite(BUZZER, LOW);
 		}
 	}
 }
 
 int main()
 {
+	//Initialize photoTaken and trigger
 	photoTaken = 0;
 	trigger = 0;
 
 	wiringPiSetup();
 	pinMode(BUTTON, INPUT);
-	pinMode(LED, OUTPUT);
-	
-	int isrSetup = wiringPiISR(BUTTON, INT_EDGE_FALLING, &myInterrupt);
+	pinMode(BUZZER, OUTPUT);
+
+	//Setup ISR (button) and I2C (gyro sensor)
+	int isrSetup = wiringPiISR(BUTTON, INT_EDGE_FALLING, &buttonInterrupt);
 	int i2cSetup = wiringPiI2CSetup(MPU3050_I2C);
 
+	//Check if setups are successful
 	if (i2cSetup < 0||isrSetup < 0)
+	{
 		return 0;
+	}
 
+	//Power I2C and begin tracking
 	wiringPiI2CWriteReg8(i2cSetup, MPU3050_PWR, 0x01);
+
+	//Declare 'gyroInput' to be used to contain the input from gyro sensor later
 	int gyroInput;
+	//Initialize 'count' to be used to keep track how many consecutive 0.1 secs had the gyro sensor stayed at 0
 	int count = 0;
-	while(1)
+
+	//Double short beep to inform rider
+	digitalWrite(BUZZER, HIGH);
+	delay(100);
+	digitalWrite(BUZZER, LOW);
+	delay(100);
+	digitalWrite(BUZZER, HIGH);
+	delay(100);
+	digitalWrite(BUZZER, LOW);
+
+	while (1)
 	{
+		//Get gyro sensor input
 		gyroInput = wiringPiI2CReadReg8(i2cSetup, MPU3050_REG);
 
-		if(gyroInput == 0)
+		if (gyroInput == 0)
 		{
+			//Increase count if gyro sensor returns 0
 			count++;
+
+			//If the gyro sensor reading stayed at '0' consecutively for over a full second
 			if (count > 10 && trigger == 0 && photoTaken == 0)
 			{
-				digitalWrite(LED, HIGH);
+				//Set off the buzzer
+				digitalWrite(BUZZER, HIGH);
+				//Allow rider 2 seconds to cancel taking photo and sending email
 				delay(2000);
 
 				if (!btnClicked)
 				{
+					/* If rider did not press the button after 2 seconds, send an email asking
+					 * for help from emergency contact attaching a photo taken on the spot
+					 */
 					system("raspistill -v -o photo.jpg && ./sendMail.sh");
 					photoTaken = 1;
 				}
 
+				//Reset button clicks
 				btnClicked = 0;
 			}
 		}
 		else
 		{
+			//Reset counter to 0
 			count = 0;
-			digitalWrite(LED, LOW);
 		}
 
+		//Only read value from gyro sensor every 0.1 sec
 		delay(100);
 	}
+
 	return 0;
 }