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Modem/afsk.c

@@ -336,7 +336,12 @@ void afsk_adc_isr(Afsk *afsk, int8_t currentSample) {
 // Signal modulation and DAC                        //
 //////////////////////////////////////////////////////
 
+// Defines how many consecutive ones we send
+// before we need "stuff" in a zero
 #define BIT_STUFF_LEN 5
+
+// A macro for switching what tone is being
+// synthesized by the DAC.
 #define SWITCH_TONE(inc)  (((inc) == MARK_INC) ? SPACE_INC : MARK_INC)
 
 static void afsk_txStart(Afsk *afsk) {
@@ -352,7 +357,7 @@ static void afsk_txStart(Afsk *afsk) {
 	ATOMIC(afsk->tailLength = DIV_ROUND(CONFIG_AFSK_TRAILER_LEN * BITRATE, 8000));
 }
 
-// This is the DAC ISR, called at sampling ratewhenever the DAC IRQ is on.
+// This is the DAC ISR, called at sampling rate whenever the DAC IRQ is on.
 // It modulates the data to be transmitted and returns a value directly
 // for output on the DAC
 uint8_t afsk_dac_isr(Afsk *afsk) {
@@ -444,7 +449,7 @@ uint8_t afsk_dac_isr(Afsk *afsk) {
 
 
 //////////////////////////////////////////////////////
-// File operation overwrites for read/write         //
+// File operation functions for read/write          //
 // These functions make the "class" act like a file //
 // pointer, which can be read from or written to.   //
 // Handy for sending and receiving data :)          //

Modem/afsk.h

@@ -1,19 +1,35 @@
+//////////////////////////////////////////////////////
+// First things first, all the includes we need     //
+//////////////////////////////////////////////////////
 
 #ifndef FSK_MODEM_H
 #define FSK_MODEM_H
 
-#include "config.h"
-#include "hardware.h"
+#include "config.h"				// Various configuration values
+#include "hardware.h"			// Hardware functions
 
-#include <cfg/compiler.h>
-#include <io/kfile.h>
-#include <struct/fifobuf.h>
+#include <cfg/compiler.h>		// Compiler info from BertOS
+#include <struct/fifobuf.h>		// FIFO buffer implementation from BertOS
+#include <io/kfile.h>			// The BertOS KFile interface. This is
+								// used for letting other functions read
+								// from or write to the modem like a
+								// file descriptor.
 
+//////////////////////////////////////////////////////
+// Our type definitions and function declarations   //
+//////////////////////////////////////////////////////
 
 #define SAMPLERATE 9600			// The rate at which we are sampling and synthesizing
 #define BITRATE    1200			// The actual bitrate at baseband. This is the baudrate.
-#define SAMPLESPERBIT (SAMPLERATE / BITRATE)	// How many DAC/ADC samples constitute on bit (8).
+#define SAMPLESPERBIT (SAMPLERATE / BITRATE)	// How many DAC/ADC samples constitute one bit (8).
 
+// This defines an errortype for a receive-
+// buffer overrun.
+#define RX_OVERRUN BV(0)
+
+// This struct defines a Hdlc parser. It will let
+// us parse the raw bits coming in from the modem
+// and synchronise to byte boundaries.
 typedef struct Hdlc
 {
 	uint8_t demodulatedBits;  	// Incoming bitstream from demodulator
@@ -22,11 +38,13 @@ typedef struct Hdlc
 	bool receiving;				// Whether or not where actually receiving data (or just noise ;P)
 } Hdlc;
 
-#define RX_OVERRUN BV(0)
-
+// This is our primary modem struct. It defines
+// all the values we need to modulate and
+// demodulate data from the physical medium.
 typedef struct Afsk
 {
-	KFile fd;
+	KFile fd;								// A file descriptor for reading from and
+											// writing to the modem
 
 	// I/O hardware pins
 	int adcPin;								// Pin for incoming signal
@@ -94,9 +112,10 @@ INLINE Afsk *AFSK_CAST(KFile *fd) {
   return (Afsk *)fd;
 }
 
-// Declare ISRs and initialization functions
+// Declare Interrupt Service Routines
+// and initialization functions
 void afsk_adc_isr(Afsk *af, int8_t sample);
 uint8_t afsk_dac_isr(Afsk *af);
 void afsk_init(Afsk *af, int adc_ch, int dac_ch);
 
-#endif
+#endif

Modem/config.h

@@ -2,12 +2,16 @@
 #ifndef FSK_CFG
 #define FSK_CFG
 
-#define CONFIG_AFSK_RX_BUFLEN 64
-#define CONFIG_AFSK_TX_BUFLEN 64
-#define CONFIG_AFSK_DAC_SAMPLERATE 9600
-#define CONFIG_AFSK_RXTIMEOUT 0
+#define CONFIG_AFSK_RX_BUFLEN 64			// The size of the modems receive buffer
+#define CONFIG_AFSK_TX_BUFLEN 64			// The size of the modems transmit buffer
+#define CONFIG_AFSK_DAC_SAMPLERATE 9600		// The samplerate of the DAC. Note that
+											// changing it here will not change the
+											// actual sample rate. It is defined here
+											// so various functions can use it.
+#define CONFIG_AFSK_RXTIMEOUT 0				// How long a read operation from the modem
+											// will wait for data before timing out.
 
-#define CONFIG_AFSK_PREAMBLE_LEN 500UL
-#define CONFIG_AFSK_TRAILER_LEN 100UL
+#define CONFIG_AFSK_PREAMBLE_LEN 250UL		// The length of the packet preamble in milliseconds
+#define CONFIG_AFSK_TRAILER_LEN 100UL		// The length of the packet tail in milliseconds
 
 #endif

Modem/hardware.c

@@ -11,7 +11,7 @@
 #include <avr/interrupt.h>	// AVR interrupt functions from BertOS
 
 // A reference to our modem "object"
-static Afsk *context;
+static Afsk *modem;
 
 //////////////////////////////////////////////////////
 // And now for the actual hardware functions        //
@@ -19,11 +19,10 @@ static Afsk *context;
 
 // This function initializes the ADC and configures
 // it the way we need.
-void hw_afsk_adcInit(int ch, Afsk *_context)
+void hw_afsk_adcInit(int ch, Afsk *_modem)
 {
 	// Store a reference to our modem "object"
-	// FIXME: rename this
-	context = _context;
+	modem = _modem;
 
 	// Also make sure that we are not trying to use
 	// a pin that can't be used for analog input
@@ -109,7 +108,7 @@ DECLARE_ISR(ADC_vect) {
 	// can't read negative voltages. By doing this simple
 	// math, we bring it back to an AC representation
 	// we can do further calculations on.
-	afsk_adc_isr(context, ((int16_t)((ADC) >> 2) - 128));
+	afsk_adc_isr(modem, ((int16_t)((ADC) >> 2) - 128));
 
 	// We also need to check if we're supposed to spit
 	// out some modulated data to the DAC.
@@ -124,7 +123,7 @@ DECLARE_ISR(ADC_vect) {
 		// we also need to trigger another pin controlled
 		// by the PORTD register. This is the PTT pin
 		// which tells the radio to open it transmitter.
-		PORTD = (afsk_dac_isr(context) & 0xF0) | BV(3); 
+		PORTD = (afsk_dac_isr(modem) & 0xF0) | BV(3); 
 	else
 		// If we're not supposed to transmit anything, we
 		// keep quiet by continously sending 128, which

Modem/main.c

@@ -1,4 +1,8 @@
 
+//////////////////////////////////////////////////////
+// First things first, all the includes we need     //
+//////////////////////////////////////////////////////
+
 #include <cpu/irq.h>		// Interrupt functionality from BertOS
 #include <cfg/debug.h>		// Debug configuration from BertOS
 
@@ -11,6 +15,11 @@
 #include "afsk.h"			// Header for AFSK modem
 #include "protocol/mp1.h"	// Header for MP.1 protocol
 
+
+//////////////////////////////////////////////////////
+// A few definitions				                //
+//////////////////////////////////////////////////////
+
 static Afsk afsk;			// Declare a AFSK modem struct
 static MP1 mp1;				// Declare a protocol struct
 static Serial ser;			// Declare a serial interface struct
@@ -30,6 +39,10 @@ static bool sertx = false;							// Flag signifying whether it's time to send da
 													// Received on the serial port.
 
 
+//////////////////////////////////////////////////////
+// And here comes the actual program :)             //
+//////////////////////////////////////////////////////
+
 // 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.

buildrev.h

@@ -1,2 +1,2 @@
-#define VERS_BUILD 371
+#define VERS_BUILD 377
 #define VERS_HOST  "vixen"