/*
 * CV
 * (or
 * knob)
 * to
 * MIDI
 * converter
 *
 * The controls go to the AVR chip's ADC pins,
   first control to AD1, second control to AD2, third to AD3
        pitch wheel to AD0
 * A switch goes to PIND2 which selects
   hi=38400 baud (serial port)
   lo=31500 baud (standard MIDI)
 *
 * Use with a 3.6864MHz crystal
*/

#include <stdarg.h>
#include <ctype.h>
#include <io4433.h>

#define xADCSR	(*(volatile unsigned char*)0x26)
#define xUCSRA  (*(volatile unsigned char*)0x2B)
//#define xUCSRB  (*(volatile unsigned char*)0x2A)

#define debug 0
#define NUM_KNOBS 3 //number of controls/pots
#define NUM_BUTTONS 5 //number of controls/pots
#define POT_CHANNEL 0x00 //midi channel to use for controllers (pots)
#define BUT_CHANNEL 0x01 //midi channel to use for effect selection (buttons)
#define IDLE_LOOPS 400 //number of loops with no midi signal before we send status of all buttons/knobs
void adc_init(void);

void adc_init(void) 
{
	outp(0x00, DDRC);
	outp(0x00, PORTC);
    outp(0x02 | (1 << ADEN)  | (1 << ADSC) | (0 << ADFR) ,   ADCSR);        //set up ADC Prescaler Divide 4 mHz by 128 ADC enable 
								//ADC Free Run   SB 20 samples per hz 
}

int main(void) 
{ 
short ain_lo, ain_hi; //analog input high and low byte
short ain; //analog in (full word)
short val[NUM_KNOBS]; //array of current controller values
short fx_on[NUM_BUTTONS]; //stores which fx are on/off
short cur_pot; //current control number (0..NUM_KNOBS-1) that we're reading in the ADC
short cur_but; //current button (0..NUM_BUTTONS-1) that we're reading from PINB
short count,count2,idle_count;
short last_baud;


if (debug){
}else{
	outp(0x00, DDRB); //portb as inputs for effect selection
	outp(0xFF, PORTB); //pull portB high
	outp(0<<PD2, DDRD);//portD pin 2 as input for baud select
	outp(1<<PD2, PORTD);//pullup portD pin 2 high
	
	adc_init();                   /* init the ADC and MUX  buffer */
	
	outp(0x00, UCSRA); 		//uart init
	outp((1<<TXEN) | (1<<RXEN), UCSRB);
	
	outp(5 , UBRR);last_baud=5;
	
	outp(0x00,  ADMUX);           /*set up mux to channel 0*/
	
	cur_pot=0;
	cur_but=0;
        idle_count=IDLE_LOOPS;

	for (count=0;count<NUM_KNOBS;count++){
		val[count]=0x40;
	}
	for (count=0;count<NUM_BUTTONS;count++){
		fx_on[count]=0x00;
	}

    for (;;)                      /* loop forever */
    {
    
    	/*********************
    	** BAUD RATE SELECT **
    	**********************/
    	
        ain_lo=inp(PIND);
        if (ain_lo & (1<<PD2)){
                ain_hi=5;          //pinD2 high means serial MIDI (38400 baud)
        }else{  //we're just using ain_hi to conserve variables :)
                ain_hi=6;           //pinD2 low means MIDI (31500 baud)
        }
        if (ain_hi!=last_baud){
                last_baud=ain_hi;
                outp(last_baud,UBRR);  //only output to UART baud reg if it changed!
        }
        
    
    	/*************************
    	**  BUTTONS: FX SELECT  **
    	**************************/
    	
		ain_lo=inp(PINB); //6 bits
		count2=((ain_lo & (1 << cur_but)) ? 0x7F : 0x00); //if the bit is set, MIDI ctrlr value = 127
		if (fx_on[cur_but]!=count2){
			fx_on[cur_but]=count2;
			
                        idle_count=0;
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(0xB0 | BUT_CHANNEL, UDR);
					//send status byte: continuous controllers
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(cur_but, UDR);
					//send data byte1: controller number (starts at controller 1 [0x00])
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(fx_on[cur_but], UDR);
					//send data byte2: value of controller (0..127)

		}
		cur_but++;
		if(cur_but>=NUM_BUTTONS) cur_but=0;

         
       	/*********************
    	**  READ CTRL VALUE **
    	**********************/

        xADCSR |= 1<<ADSC;
    	do{ } while(!(xADCSR & (1<<ADIF)));     // Wait for A/D conversion to finish
        xADCSR |= 1<<ADIF;			  			// Clear the flag
   
		ain_lo = inp(ADCL);						//eight bits
		ain_hi = inp(ADCH);						//two bits
		
		
	/*********************
    	**  CTRL MIDI OUT   **
    	**********************/

		ain=(ain_hi << 5) |  (ain_lo>>3);
			//scale the 10 bit value to a 7 bit value (0..127)
	
		if (((val[cur_pot]-ain)>1) || ((val[cur_pot]-ain)<-1)){	//if this control's value has changed...
			val[cur_pot]=ain; 	//...update the array of control values

                        idle_count=0;
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(0xB0 | POT_CHANNEL, UDR);
					//send status byte: continuous controllers
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(cur_pot, UDR);
					//send data byte1: controller number (starts at controller 1 [0x00])
			while ( !(xUCSRA & (1<<UDRE)) ) ;
			outp(val[cur_pot], UDR);
					//send data byte2: value of controller (0..127)
		}

        /**********************
        ** IDLE MIDI UPDATES **
        ***********************/

                idle_count++;
                if (idle_count>=IDLE_LOOPS){
                 	for (count=0;count<NUM_KNOBS;count++){
		      	     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(0xB0 | POT_CHANNEL, UDR);
					//send status byte: continuous controllers
			     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(count, UDR);
					//send data byte1: controller number (starts at controller 1 [0x00])
			     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(val[count], UDR);
					//send data byte2: value of controller (0..127)
                	}
                	for (count2=0;count2<NUM_BUTTONS;count2++){
			     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(0xB0 | BUT_CHANNEL, UDR);
					//send status byte: continuous controllers
			     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(count2, UDR);
					//send data byte1: controller number (starts at controller 1 [0x00])
			     while ( !(xUCSRA & (1<<UDRE)) ) ;
			     outp(fx_on[count2], UDR);
					//send data byte2: value of controller (0..127)
                	}

                        idle_count=0;

                }

		count=1000;do{
			count2=10;while (--count2);
		} while(--count) ;

		cur_pot++;
		if(cur_pot>=NUM_KNOBS) cur_pot=0;

		outp(cur_pot ,ADMUX);	//set up mux to read next control


        count = 66;                          
        do{ } while(--count);                   // wait some cycles
        
   } //endless loop
} //if debug
} //main()