K3-2KL band decoder suitable for ATtiny2313. (This code is under review.)

k3-2kl-banddec.c

/*
  -- A K3-2KL band decoder suitable for ATtiny2313.
  -- (C) 2011 B1Z.
  -- Currently, nothing about licensing is considered.
  -- Author: BD1ES.

  -- Comments:
  -- The chip should be configured to enable the internal "RC clock div 8."
  -- That is, the main frequency of the CPU is 1 MHz.
 */

#include <avr/io.h>
#include <avr/pgmspace.h>

// Define D/A values corresponding to 2KL input voltages.
#define BAND_28     BAND_VALUE(2.25)
#define BAND_24     BAND_VALUE(2.25)
#define BAND_21     BAND_VALUE(3.25)
#define BAND_18     BAND_VALUE(3.25)
#define BAND_14     BAND_VALUE(4.25)
#define BAND_10     BAND_VALUE(0.6)
#define BAND_7      BAND_VALUE(5.25)
#define BAND_3M5    BAND_VALUE(6.25)
#define BAND_1M8    BAND_VALUE(7.5)
#define BAND_UNDEF  BAND_VALUE(2.25)

// Since
// Vout = (DAout/128)*Vref*(1+Rf/Ra),
// DAout = 128*Vout*Ra/(Vref*(Ra+Rf)),
// and Rf = 6k, Ra = 10k, Vref = 5.0,
// therefore:
#define BAND_VALUE(band_volt) (128 * band_volt * 10 / (5.0 * (10 + 6)) + 0.5)

// Define a table for mapping bands from K3 to 2KL.
static uint8_t PROGMEM band_value[16] = {
    BAND_UNDEF, BAND_1M8,   BAND_3M5,   BAND_7,
    BAND_10,    BAND_14,    BAND_18,    BAND_21,
    BAND_24,    BAND_28,    BAND_UNDEF, BAND_UNDEF,
    BAND_UNDEF, BAND_UNDEF, BAND_UNDEF, BAND_UNDEF
};

// Define a table for preventing invalid band combination input.
static uint8_t PROGMEM band_valid[16] = {
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0
};

// Hardware dependent routines.
static void init_io(void)
{
    // Port A(1..0) pull up.
    DDRA = 0;
    PORTA = (1<<PA1) | (1<<PA0);

    // Port D(5..2) pull up.
    DDRD = 0;
    PORTD = (1<<PD5) | (1<<PD4) | (1<<PD3) | (1<<PD2);

    // Port B output.
    PORTB = 0;
    DDRB = 0xff;
}

static uint8_t read_k3_on(void)
{
    return PINA & (1<<PA0);
}

static uint8_t read_key_out_lp(void)
{
    return PINA & (1<<PA1);
}

static uint8_t read_band(void)
{
    uint8_t value = 0;

    if(PIND & (1<<PD2)) value |= 0x08;
    if(PIND & (1<<PD3)) value |= 0x04;
    if(PIND & (1<<PD4)) value |= 0x02;
    if(PIND & (1<<PD5)) value |= 0x01;

    return value;
}

static void write_port_b(uint8_t value)
{
    PORTB = value;
}

// The main program.
int main()
{
    // Init I/O.
    init_io();

    // Main loop.
    while(1){
        // Read signals representing the band and the PTT from the input.
        uint8_t band = read_band();

        // Forward the PTT signal and the converted D/A value to the output.
        if(pgm_read_byte(&band_valid[band]) && read_k3_on() &&
          (read_key_out_lp() == 0)){
            write_port_b(pgm_read_byte(&band_value[band]) | 0x80);
        }else{
            write_port_b(pgm_read_byte(&band_value[band]) & 0x7f);
        }
    }

    return 0;
}