Tiny morse beacon keyer in an ATTiny85

Using some code based on the excellent example here I built a morse beacon keyer using an ATMega8 but it seemed like a massive waste of pins so I ordered a bunch of the 8 pin ATTiny85 chips from Digi-key. (Great service by the way)

With just 8 pins, if you use the internal oscillator, you get 6 available pins for input and output which is really quite a lot for many simple tasks like this.

In the code below, pin 5 is the keyer output, pin 6 is an inverted version and pin 7 is an audio side tone output.

My code is a simplification and an extension (to include the full alphabet and make a side tone) of the code that is "© 1997-2006 by AWC, 310 Ivy Glen, League City, TX 77573" so I hope it's ok to present it here:

/*
    Morse ident, based on code from:
    http://www.awce.com/cbasic.htm
*/

#include 
#include 
#define F_CPU 800000UL	      // Sets up the default speed for delay.h
#include 
#include 

/* dit delay for morse code */
#define DITDELAY 50  /* mS */
#define OUTPORT PORTB
#define OUTPORTDIRECTION DDRB

// the normal output bit
#define OUTBIT 0

// inverted version out bit
#define INVERTED_OUTBIT 1

// tone output bit
#define TONE_OUTBIT 2

void sendchar(int c);
void tone(int length);

int main (void)
{
    // Put beacon message in program memory
    PGM_P *message=PSTR("cq cq cq cq de vk2tpm ");
    OUTPORTDIRECTION = _BV(OUTBIT) | _BV(INVERTED_OUTBIT) | _BV(TONE_OUTBIT);
    
    while (1) 
    {
        int c;
        // Send each character in message
        PGM_P ptr=message;
        for (c=pgm_read_byte(ptr); c; c=pgm_read_byte(++ptr))
        {
            sendchar(c);
        }
        _delay_ms(30000);  // wait 30 seconds
    }
    return 0;
}

/* Send a Morse code element (.- or space) */
void send(char c)
{
    switch (c)
    {
        case '-':
            OUTPORT = _BV(OUTBIT);
            tone(3*DITDELAY);
            OUTPORT = _BV(INVERTED_OUTBIT);
            break;
        case '.':
            OUTPORT = _BV(OUTBIT);
            tone(DITDELAY);
            OUTPORT = _BV(INVERTED_OUTBIT);
            break;
    case ' ':
        _delay_ms(4*DITDELAY);
        break;
    }
    _delay_ms(DITDELAY);  /* inter element space */
}

// play a tone for the given length
void tone(int length)
{
    int i;
    for(i = 0; i < length; i++)
    {
        // leave the other bits in place
        OUTPORT ^= _BV(TONE_OUTBIT);
        _delay_ms(2);
    }
}
// Send a character (made from dots/dashes) from program memory
void sendc(PGM_P s)
{
    int c;
    for (c=pgm_read_byte(s);c;c=pgm_read_byte(++s)) 
    {
        send(c);
    }
}
// Send an ASCII character
void sendchar(int c)
{
    switch (toupper(c))
    {
        case ' ': sendc(PSTR(" ")); break;
        case 'A': sendc(PSTR(".-")); break;
        case 'B': sendc(PSTR("-...")); break;
        case 'C': sendc(PSTR("-.-.")); break;
        case 'D': sendc(PSTR("-..")); break;
        case 'E': sendc(PSTR(".")); break;
        case 'F': sendc(PSTR("..-.")); break;
        case 'G': sendc(PSTR("--.")); break;
        case 'H': sendc(PSTR("....")); break;
        case 'I': sendc(PSTR("..")); break;
        case 'J': sendc(PSTR(".---")); break;
        case 'K': sendc(PSTR("-.-")); break;
        case 'L': sendc(PSTR(".-..")); break;
        case 'M': sendc(PSTR("--")); break;
        case 'N': sendc(PSTR("-.")); break;
        case 'O': sendc(PSTR("---")); break;
        case 'P': sendc(PSTR(".--.")); break;
        case 'Q': sendc(PSTR("--.-")); break;
        case 'R': sendc(PSTR(".-.")); break;
        case 'S': sendc(PSTR("...")); break;
        case 'T': sendc(PSTR("-")); break;
        case 'U': sendc(PSTR("..-")); break;
        case 'V': sendc(PSTR("...-")); break;
        case 'W': sendc(PSTR(".--")); break;
        case 'X': sendc(PSTR("-..-")); break;
        case 'Y': sendc(PSTR("-.--")); break;
        case 'Z': sendc(PSTR("--..")); break;
        case '1': sendc(PSTR(".----")); break;
        case '2': sendc(PSTR("..---")); break;
        case '3': sendc(PSTR("...--")); break;
        case '4': sendc(PSTR("....-")); break;
        case '5': sendc(PSTR(".....")); break;
        case '6': sendc(PSTR("-....")); break;
        case '7': sendc(PSTR("--...")); break;
        case '8': sendc(PSTR("---..")); break;
        case '9': sendc(PSTR("----.")); break;
        case '0': sendc(PSTR("-----")); break;
    }
    send(' ');
}

When I burn it with the fabulous AVRDUDE I get:

Writing | ################################################## | 100% 34.10s

avrdude: 1026 bytes of flash written

avrdude: safemode: lfuse reads as 62
avrdude: safemode: hfuse reads as DF
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK

avrdude done.  Thank you.

So the code uses just 1026 bytes out of the available 8k which means a lot more can be done on one of these chips.