Commenting

Modem/main.c

@@ -1,79 +1,120 @@
 
-#include <cpu/irq.h>
-#include <cfg/debug.h>
+#include <cpu/irq.h>		// Interrupt functionality from BertOS
+#include <cfg/debug.h>		// Debug configuration from BertOS
+
+#include <drv/ser.h>		// Serial driver from BertOS
+#include <drv/timer.h>		// Timer driver from BertOS
+
+#include <stdio.h>			// Standard input/output
+#include <string.h>			// String operations
 
 #include "afsk.h"			// Header for AFSK modem
 #include "protocol/mp1.h"	// Header for MP.1 protocol
 
-#include <drv/ser.h>
-#include <drv/timer.h>
+static Afsk afsk;			// Declare a AFSK modem struct
+static MP1 mp1;				// Declare a protocol struct
+static Serial ser;			// Declare a serial interface struct
 
-#include <stdio.h>
-#include <string.h>
+#define ADC_CH 0			// Define which channel (pin) we want
+							// for the ADC (this is A0 on arduino)
 
-static Afsk afsk;
-static Serial ser;
+#define TEST_TX false		// Whether we should send test packets
+							// periodically, plus what to send:
+#define TEST_PACKET "Test MP1 AFSK Packet. This is a test. 1234567890. ABCDEFGHIJKLMNOPQRSTUVWXYZ."
 
-static MP1 mp1;
 
-#define ADC_CH 0
+static uint8_t serialBuffer[MP1_MAX_FRAME_LENGTH];	// This is a buffer for incoming serial data
+static int sbyte;									// For holding byte read from serial port
+static int serialLen = 0;							// Counter for counting length of data from serial
+static bool sertx = false;							// Flag signifying whether it's time to send data
+													// Received on the serial port.
 
-#define TEST_PACKET "Test MP1 AFSK Packet! This one is longer and probably more prone to errors..."
-
-static uint8_t serialBuffer[MP1_MAX_FRAME_LENGTH];
-static int sbyte;
-static uint8_t serialLen = 0;
-static bool sertx = false;
 
+// This is a callback we register with the protocol,
+// so we can process each packet as they are decoded.
+// Right now it just prints the packet to the serial port.
 static void mp1Callback(struct MP1Packet *packet) {
 	kfile_printf(&ser.fd, "%.*s\r\n", packet->dataLength, packet->data);
 }
 
+// Simple initialization function.
 static void init(void)
 {
+	// Enable interrupts
 	IRQ_ENABLE;
+	// Initialize BertOS debug bridge
 	kdbg_init();
     kprintf("Init\n");
 
+    // Initialize hardware timers
 	timer_init();
 
-	afsk_init(&afsk, ADC_CH, 0);
-	mp1Init(&mp1, &afsk.fd, mp1Callback);
-
+	// Initialize serial comms on UART0,
+	// which is the hardware serial on arduino
 	ser_init(&ser, SER_UART0);
 	ser_setbaudrate(&ser, 57600);
-	//ser_settimeouts(&ser, 0, 0);
+
+	// Create a modem context
+	afsk_init(&afsk, ADC_CH, 0);
+	// ... and a protocol context with the modem
+	mp1Init(&mp1, &afsk.fd, mp1Callback);
+
+	// That's all!
 }
 
 int main(void)
 {
+	// Start by running the main initialization
 	init();
+	// Record the current tick count for time-keeping
 	ticks_t start = timer_clock();
 	
+	// Go into ye good ol' infinite loop
 	while (1)
 	{
+		// First we instruct the protocol to check for
+		// incoming data
 		mp1Poll(&mp1);
 
+		// We then read a byte from the serial port.
+		// Notice that we use "_nowait" since we can't
+		// have this blocking execution until a byte
+		// comes in.
 		sbyte = ser_getchar_nowait(&ser);
+		// If there was actually some data waiting for us
+		// there, let's se what it tastes like :)
 		if (sbyte != EOF) {
-			if (serialLen < MP1_MAX_FRAME_LENGTH && sbyte != 138) {
+			// If we have not yet surpassed the maximum frame length
+			// and the byte is not a "transmit" (newline) character,
+			// we should store it for transmission.
+			if ((serialLen < MP1_MAX_FRAME_LENGTH) && (sbyte != 138)) {
+				// Put the read byte into the buffer;
 				serialBuffer[serialLen] = sbyte;
+				// Increment the read length counter
 				serialLen++;
 			} else {
+				// If one of the above conditions were actually the
+				// case, it means we have to transmit, se we set
+				// transmission flag to true.
 				sertx = true;
 			}
 		}
 
+		// Check whether we should send data in our serial buffer
 		if (sertx) {
+			// If we should, pass the buffer to the protocol's
+			// send function.
 			mp1Send(&mp1, serialBuffer, serialLen);
+			// Reset the transmission flag and length counter
 			sertx = false;
 			serialLen = 0;
 		}
 
-		// Periodically send test data
-		if (false && timer_clock() - start > ms_to_ticks(4000L))
-		{
+		// Periodically send test data if we should do so
+		if (TEST_TX && timer_clock() - start > ms_to_ticks(15000L)) {
+			// Reset the timer counter;
 			start = timer_clock();
+			// And send a test packet!
 			mp1Send(&mp1, TEST_PACKET, sizeof(TEST_PACKET));
 		}
 	}