gistfile1.c

#include <string.h>
#include <stdlib.h>

#define BEEPER_PIN 2

#define UNIT_MS 50
#define UNIT_US (1000L * UNIT_MS)

#define DOT 0
#define DASH 1
#define WAIT_3 2 // end of a letter
#define WAIT_7 3 // end of a word

const int morse_map[][6] = {
	{ DOT,	DASH,			WAIT_3 }, // A
	{ DASH,	DOT,	DOT,	DOT,	WAIT_3 }, // B
	{ DASH,	DOT,	DASH,	DOT,	WAIT_3 }, // C
	{ DASH,	DOT,	DOT,		WAIT_3 }, // D
	{ DOT,				WAIT_3 }, // E
	{ DOT,	DOT,	DASH,	DOT,	WAIT_3 }, // F
	{ DASH,	DASH,	DOT,		WAIT_3 }, // G
	{ DOT,	DOT,	DOT,	DOT,	WAIT_3 }, // H
	{ DOT,	DOT,			WAIT_3 }, // I
	{ DOT,	DASH,	DASH,	DASH,	WAIT_3 }, // J
	{ DASH,	DOT,	DASH,		WAIT_3 }, // K
	{ DOT,	DASH,	DOT,	DOT,	WAIT_3 }, // L
	{ DASH,	DASH,			WAIT_3 }, // M
	{ DASH,	DOT,			WAIT_3 }, // N
	{ DASH,	DASH,	DASH,		WAIT_3 }, // O
	{ DOT,	DASH,	DASH,	DOT,	WAIT_3 }, // P
	{ DASH,	DASH,	DOT,	DASH,	WAIT_3 }, // Q
	{ DOT,	DASH,	DOT,		WAIT_3 }, // R
	{ DOT,	DOT,	DOT,		WAIT_3 }, // S
	{ DASH,				WAIT_3 }, // T
	{ DOT,	DOT,	DASH,		WAIT_3 }, // U
	{ DOT,	DOT,	DOT,	DASH,	WAIT_3 }, // V
	{ DOT,	DASH,	DASH,		WAIT_3 }, // W
	{ DASH,	DOT,	DOT,	DASH,	WAIT_3 }, // X
	{ DASH,	DOT,	DASH,	DASH,	WAIT_3 }, // Y
	{ DASH,	DASH,	DOT,	DOT,	WAIT_3 }  // Z
};

int *morse_sequence = NULL;
int morse_length = 0;
int sequence_idx = 0;

/**
 * add_char_to_sequence - Add a character to the morse code sequence
 * @c:	Character to add
 *
 * Copy over the corresponding sequence from morse_map, if it's a space just
 * append a WAIT_7
 */
static void add_char_to_sequence(const char c)
{
	// 7 unit wait for spaces
	if (c == ' ') {
		morse_sequence = (int*)(
				realloc(morse_sequence, morse_length + 1));
		morse_sequence[morse_length++] = WAIT_7;
		return;
	}
	// string must be all caps alphabetical
	if (c < 'A' || c > 'Z')
		return;

	const int map_idx = c - 'A';
	const int start_idx = morse_length;

	// update the buffer size
	for (int i = 0; morse_map[map_idx][i] != WAIT_3; i++)
		morse_length++;

	morse_length++; // need an extra space to copy the wait
	morse_sequence = (int*)(realloc(morse_sequence, morse_length));

	// copy the sequence over
	const int copy_size = (morse_length - start_idx) * sizeof(int);
	memcpy(&morse_sequence[start_idx], morse_map[map_idx], copy_size);
}

/**
 * setup - Initialization function
 *
 * Generate a sequence of morse code
 */
void setup()
{
	const char *string = "ACD ON TOP";
	const int len = strlen(string);

	for (int i = 0; i < len; i++)
		add_char_to_sequence(string[i]);

	// initialize the beeper pin
	pinMode(BEEPER_PIN, OUTPUT);
}

/**
 * beep - Beep at the specified interval
 * @interval_us:	Interval in microseconds
 * @time_us:		Time to beep in microseconds
 *
 * Loop and use delayMicroseconds to beep every interval_us. Add interval_us to
 * a counter and break when it reaches time_us.
 */
static void beep(const long interval_us, const long time_us)
{
	const long delay_us = interval_us / 2;
	for (long i = 0; i < time_us; i += interval_us) {
		digitalWrite(BEEPER_PIN, HIGH);
		delayMicroseconds(delay_us);
		digitalWrite(BEEPER_PIN, LOW);
		delayMicroseconds(delay_us);
	}
	delay(UNIT_MS);
}

/**
 * loop - Main loop
 *
 * Play the morse code sequence through the beeper
 */
void loop()
{
	const int cmd = morse_sequence[sequence_idx];
	if (cmd == DOT)
		beep(500, UNIT_US);
	else if (cmd == DASH)
		beep(2000, UNIT_US * 3);
	else if (cmd == WAIT_3)
		delay(UNIT_MS * 3);
	else if (cmd == WAIT_7)
		delay(UNIT_MS * 7);

	if (++sequence_idx == morse_length) {
		// restart sequence
		sequence_idx = 0;
		delay(3000);
	}
}