//sched2 modified to include NON-BLOCKING serial code 
//used as an example in the program organization doc.      
             
#include <90s8515.h> 
#include <stdio.h>       //for debugging using printf, etc

//timeout values for each task
#define t1 60  
#define t2 250 
#define t3 50 

//I like these definitions
#define begin {
#define end   }
 
//timer 1 constants 
#define prescale1 1
#define clear_on_match 8

//the  subroutines
void task1(void);  		//test for button press
void task2(void);		//increment note to be played  
void task3(void);		//check the serial line for commands
void initialize(void); 	//all the usual mcu stuff 
          
unsigned char reload;				//timer 0 reload to set 1 mSec
unsigned char time1, time2, time3;	//task scheduleing timeout counters
unsigned char cmd_ready;			//set when command is received
unsigned char cmd;					//'p'=play 's'=stop 			  
unsigned char note;					//current note to be played... 
									//task 1 sets note to 0 to start song
    
//****************************************************
//table of periods for 1 cycle of each musical note in 1/4 microsec ticks
//
//   note   freq    period in
//           Hz    1/4 microsec
//
//    C4    262    15267
//    D4    294    13605
//    E4    330    12121
//    F4    349    11461
//    G4    392    10204
//    A4    440    9090
//    B4    494    8097
//    C5    523    7648  
// put the notes in flash to save RAM    
flash int notetable[8]={15267/2, 13605/2, 12121/2, 11461/2, 10204/2, 9090/2, 8097/2, 7648/2}; 

//**********************************************************
//timer 0 overflow ISR
interrupt [TIM0_OVF] void timer0_overflow(void)
begin   
    
  //reload to force 1 mSec overflow
  TCNT0=reload;
  
  //Decrement the three times if they are not already zero
  if (time1>0)	--time1;
  if (time2>0) 	--time2;
  if (time3>0) 	--time3;
end  
 
//**********************************************************
//timer 1 compare-match A ISR
interrupt [TIM1_COMPA] void cmpA_overflow(void)  
begin       
  PORTC = ~PORTC ; 	//toggle the port to make a sound
end  
 
//**********************************************************       
//Entry point and task scheduler loop
void main(void)
begin  
  initialize();
  
  //main task scheduler loop -- never exits!
  while(1)
  begin     
    if (time1==0)	task1();
    if (time2==0) 	task2();
    if (time3==0) 	task3();
  end   
end  
  
//**********************************************************          
//Task 1   -- detect a pusbutton
void task1(void) 
begin  
  time1=t1;  				//reset the task timer 
  
  //turn on the scale
  if (~PIND == 0x01 || (cmd_ready && cmd=='p') ) 
  begin
  	note=0;  			   			    	//check for button push or 'p' 
  	PORTB=0xfe;			   			    	//turn on the LED
  	cmd_ready=0;
  end  
     
  //kill it
  if (~PIND == 0x02 || (cmd_ready && cmd=='s')) 
  begin
  	note=8;  				//check for button push or 's'
  	TCCR1B = 0;				 //and turn off timer 1 
  	PORTB=0xfd;				//turn on the LED 
  	cmd_ready=0;
  end        
  
  //LEDs off
  if (~PIND == 0x00) 
  begin 
  	PORTB=0xff;				//turn off the LEDs
  end
end  
 
//********************************************************** 
//Task 2  -- detect start/end of scale and increment the note
void task2(void) 
begin
  time2=t2;  				//reset the task timer  
  if (note < 8)  			//play a note? or are we done?
  begin 
    TCNT1=0;   
    OCR1A=notetable[note]; 	//and load the correct time out for timer 1  
    ++note ; 	   			//play the next note when task 2 enters again
    TCCR1B = prescale1 + clear_on_match ; //start timer 2
  end 
  else TCCR1B=0;			//turn off timer 1 
end  
  
//********************************************************** 
//Task 3  -- non-blocking keyboard check every 50 mSec
void task3(void) 
begin
  time3=t3;
  if (USR.7)   		//RX done bit
  begin
  	cmd=getchar(); 
  	putchar(cmd); 
  	putsf("\r\n");
  	cmd_ready=1;
  end
end

//********************************************************** 
//Set it all up
void initialize(void)
begin
  //set up the ports
  DDRD=0x00;	// PORT D is an input
  DDRC=0xff;    // PORT C is an ouput  
  DDRB=0xff;	//PORT B is an output for leds
  PORTC=0; 
  PORTB=0xff;  //all LEDs off
   
  //serial setop for debugging using printf, etc.     
  UCR = 0x10 + 0x08 ;
  UBRR = 25 ;
           
  //set up timer 0     
  //62.5 x (64x.25) microSec = 1.0 mSec, so prescale 64, and count 62 times.
  reload=256-62; //value for 1 Msec  
  TCNT0=reload;	 //preload timer 1 so that is interrupts after 1 mSec.
  TCCR0=3;		//prescalar to 64
  TIMSK=2;	   	//turn on timer 0 overflow ISR  
  
  //set up timer 1
  TIMSK=TIMSK | 0x40;	//turn on timer 1 compare match interrupt
  TCCR1B = 0;			//disable timer 1 until song starts  
  TCNT1 = 0;     		//and zero the timer 
  
  //init the task timers
  time1=t1;
  time2=t2;    
                 
  //init the current note 8 => all done
  //song starts when task 1 sets note to 0
  note=8;
      
  //crank up the ISRs
  #asm
  	sei
  #endasm 
end