/*

 * ax25.c

 *

 * Created: 10/30/2012 12:16:41 PM

 *  Author: ethanzonca

 */ 

/*

#include <inttypes.h>

#include "afsk.h"

// Module constants

#define MAX_PACKET_LEN 512  // bytes

// Module globals

static uint16_t crc;

static uint8_t ones_in_a_row;

static uint8_t packet[MAX_PACKET_LEN];

static unsigned int packet_size;

// Module functions

void update_crc(uint8_t a_bit)

{

	crc ^= a_bit;

	if (crc & 1)

	crc = (crc >> 1) ^ 0x8408;  // X-modem CRC poly

	else

	crc = crc >> 1;

}

void send_byte(uint8_t a_byte)

{

	uint8_t i = 0;

	while (i++ < 8) {

		uint8_t a_bit = a_byte & 1;

		a_byte >>= 1;

		update_crc(a_bit);

		if (a_bit) {

			// Next bit is a '1'

			if (packet_size >= MAX_PACKET_LEN * 8)  // Prevent buffer overrun

			return;

			packet[packet_size >> 3] |= (1 << (packet_size & 7));

			packet_size++;

			if (++ones_in_a_row < 5) continue;

		}

		// Next bit is a '0' or a zero padding after 5 ones in a row

		if (packet_size >= MAX_PACKET_LEN * 8)    // Prevent buffer overrun

		return;

		packet[packet_size >> 3] &= ~(1 << (packet_size & 7));

		packet_size++;

		ones_in_a_row = 0;

	}

}

// Exported functions

void ax25_send_byte(uint8_t a_byte)

{

	// Wrap around send_byte, but prints debug info

	send_byte(a_byte);

}

void ax25_send_flag()

{

	uint8_t flag = 0x7e;

	int i;

	for (i = 0; i < 8; i++, packet_size++) {

		if (packet_size >= MAX_PACKET_LEN * 8)  // Prevent buffer overrun

		return;

		if ((flag >> i) & 1)

		packet[packet_size >> 3] |= (1 << (packet_size & 7));

		else

		packet[packet_size >> 3] &= ~(1 << (packet_size & 7));

	}

}

void ax25_send_string(const char *string)

{

	int i;

	for (i = 0; string[i]; i++) {

		ax25_send_byte(string[i]);

	}

}

void ax25_send_header(const struct s_address *addresses, int num_addresses)

{

	int i, j;

	packet_size = 0;

	ones_in_a_row = 0;

	crc = 0xffff;

	// Send flags during TX_DELAY milliseconds (8 bit-flag = 8000/1200 ms)

	for (i = 0; i < TX_DELAY * 3 / 20; i++) {

		ax25_send_flag();

	}

	for (i = 0; i < num_addresses; i++) {

		// Transmit callsign

		for (j = 0; addresses[i].callsign[j]; j++)

		send_byte(addresses[i].callsign[j] << 1);

		// Transmit pad

		for ( ; j < 6; j++)

		send_byte(' ' << 1);

		// Transmit SSID. Termination signaled with last bit = 1

		if (i == num_addresses - 1)

		send_byte(('0' + addresses[i].ssid) << 1 | 1);

		else

		send_byte(('0' + addresses[i].ssid) << 1);

	}

	// Control field: 3 = APRS-UI frame

	send_byte(0x03);

	// Protocol ID: 0xf0 = no layer 3 data

	send_byte(0xf0);

}

void ax25_send_footer()

{

	// Save the crc so that it can be treated it atomically

	uint16_t final_crc = crc;

	// Send the CRC

	send_byte(~(final_crc & 0xff));

	final_crc >>= 8;

	send_byte(~(final_crc & 0xff));

	// Signal the end of frame

	ax25_send_flag();

}

void ax25_flush_frame()

{

	// Key the transmitter and send the frame

	afsk_send(packet, packet_size);

	afsk_start();

}*/

/*

 * ax25.h

 *

 * Created: 10/30/2012 12:14:05 PM

 *  Author: ethanzonca

 */ 

#ifndef AX25_H_

#define AX25_H_

#endif /* AX25_H_ */