/* Copyright 2010, 2011 Ethan Blanton <elb@psg.com> */

/* This example blinks P1.0 in morse code, sending the message in the
 * variable 'str' in main(). */

#include <io.h>
#include <signal.h>

#define MORSE_NONE 0x01

#define DELAY_DIT 0x5555
#define DELAY_DAH 0xFFFF

/* Each byte is prefixed with a variable number of zero bits and a
 * single 1, followed by the morse code representation of the
 * character where 0 = dit and 1 = dah.  For example, the character
 * e is 0b0000 0010; that is, six prefix 0s, a 1 to indicate the
 * beginning of the character, and a single 0 represinting the dit.
 * The table is in ASCII order, so indexing a character into the
 * table directly yields its morse representation.  The character
 * set is incomplete.  (Notably, some symbols and all prosigns are
 * missing.)  Missing characters cause a dah-length inter-character
 * delay with no intervening symbols. */
const unsigned char morse_ascii[] = {
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    0x73, MORSE_NONE, 0x55, 0x32,                   /* , _ . / */
    0x3F, 0x2F, 0x27, 0x23,                         /* 0 1 2 3 */
    0x21, 0x20, 0x30, 0x38,                         /* 4 5 6 7 */
    0x3C, 0x37, MORSE_NONE, MORSE_NONE,             /* 8 9 _ _ */
    MORSE_NONE, 0x31, MORSE_NONE, 0x4C,             /* _ = _ ? */
    MORSE_NONE, 0x05, 0x18, 0x1A,                   /* _ A B C */
    0x0C, 0x02, 0x12, 0x0E,                         /* D E F G */
    0x10, 0x04, 0x17, 0x0D,                         /* H I J K */
    0x14, 0x07, 0x06, 0x0F,                         /* L M N O */
    0x16, 0x1D, 0x0A, 0x08,                         /* P Q R S */
    0x03, 0x09, 0x11, 0x0B,                         /* T U V W */
    0x19, 0x1B, 0x1C, MORSE_NONE,                   /* X Y Z _ */
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
    MORSE_NONE, 0x05, 0x18, 0x1A,                   /* _ A B C */
    0x0C, 0x02, 0x12, 0x0E,                         /* D E F G */
    0x10, 0x04, 0x17, 0x0D,                         /* H I J K */
    0x14, 0x07, 0x06, 0x0F,                         /* L M N O */
    0x16, 0x1D, 0x0A, 0x08,                         /* P Q R S */
    0x03, 0x09, 0x11, 0x0B,                         /* T U V W */
    0x19, 0x1B, 0x1C, MORSE_NONE,                   /* X Y Z _ */
    MORSE_NONE, MORSE_NONE, MORSE_NONE, MORSE_NONE,
};

/* This delays for roughly four cycles per iteration, plus a
 * couple of cycles of overhead.  (See the compiler-generated code
 * to determine exactly how many cycles per iteration!) */
void delay(unsigned int d) {
    for (; d > 0; d--) {
       nop();
       nop();
    }
}

int main(void) {
    /* It is important that this string be some immutable data type, to
     * prevent the compiler from copying it to RAM.  const char str[] is
     * *not* treated as immutable, and leads to the compiler a) using a
     * pile of RAM for the string, and b) inserting a 266-byte (!)
     * memcpy implementation in the binary in ROM. */
    const char *str = "hello de KB8OJH";
    unsigned int i;

    WDTCTL = WDTPW | WDTHOLD;
    P1DIR  = 0x1;

    /* Loop forever */
    while (1) {
        /* Send the string in str as morse code */
        for (i = 0; str[i]; i++) {
            int inchar = 0; /* Indicates whether we are in the prefix
                             * padding or the character itself. */
            unsigned int j;
            for (j = 0; j < 8; j++) {
                /* The following lookup yields true for dah and false
                 * for dit at each position */
                int bit = morse_ascii[(int)str[i]] & (0x80 >> j);
                if (inchar) {
                   /* Set the output pin, delay for dit or dah
                    * period according to bit, then unset the
                    * output pin. */
                    P1OUT = 1;
                    delay(bit ? DELAY_DAH : DELAY_DIT);
                    P1OUT = 0;
                    if (j < 7) {
                        /* If we're not yet to the end of the character,
                         * delay one dit period for intra-char delay */
                        delay(DELAY_DIT);
                    }
                } else if (bit) {
                    /* This is the end of the padding, set inchar
                     * and iterate. */
                    inchar = 1;
                }
            }
            delay(DELAY_DAH); /* Inter-character delay. */
        }
        /* Delay two more dahs at the end of the string, before we
         * repeat. */
        delay(DELAY_DAH);
        delay(DELAY_DAH);
    }
}