/******* Tones.c ***************
 *
 * Use RPG to change tone on RC2/CCP1 output over two octaves,
 * from  C = 523 Hz to C = 2093 Hz.
 *
 * VDD = 5V.
 * Use Fosc = 4 MHz for Fcpu = Fosc/4 = 1 MHz.
 *      Current draw = 2.20 mA
 *
 *      Current draw without piezo speaker = 2.14 mA
 *
 ******* Program hierarchy *****
 *
 * main
 *    Initial
 *    Tone
 *    RPG
 *
 *******************************
 */

#include <p18f4321.h>           // Define PIC18LF4321 registers and bits

/*******************************
 * Configuration selections
 *******************************
 */

#pragma config OSC = INTIO1     // Use internal osc, RA6=Fosc/4, RA7=I/O
#pragma config PWRT = ON        // Enable power-up delay
#pragma config LVP = OFF        // Disable low-voltage programming
#pragma config WDT = OFF        // Disable watchdog timer initially
#pragma config WDTPS = 4        // 16 millisecond WDT timeout period, nominal
#pragma config MCLRE = ON       // Enable master clear pin
#pragma config PBADEN = DIG     // PORTB<4:0> = digital
#pragma config CCP2MX = RB3     // Connect CCP2 internally to RB3 pin
#pragma config BOR = SOFT       // Brown-out reset controlled by software
#pragma config BORV = 3         // Brown-out voltage set for 2.1V, nominal
#pragma config LPT1OSC = OFF    // Deselect low-power Timer1 oscillator

/*******************************
 * Global variables
 *******************************
 */
unsigned int DELAY;             // Counter for obtaining a delay
unsigned char ALIVECNT;         // Counter for blinking "Alive" LED
char COUNT;                     // Counter available as local to subroutines
char DELRPG;                    // RPG output
unsigned int HALFPERIOD;        // Value to be reloaded into Timer1
unsigned char OLDPORTB;         // Value of PORTB from last loop time
const rom int *romPtr;          // Pointer into ROM strings
signed char NOTENUM;         	// Number of the note to be played 0,...,12

/*******************************
 * Constant strings
 *******************************
 */
const rom int Notes[] = {956 ,851,758,716,638,568,506, 478 ,426,379,358,319,284,253, 239};
                                // Half period microseconds for two octaves
/*******************************
 * Function prototypes
 *******************************
 */
void Initial(void);
void RPG(void);
void Tone(void);

/*******************************
 * Macros
 *******************************
 */
#define Delay(x) DELAY = x; while(--DELAY){ Nop(); Nop(); }

/////// Main program /////////////////////////////////////////////////////

/*******************************
 * main
 *******************************
 */
void main()
{
   Initial();                   // Initialize everything
   while (1)
   {
      RPG();
      Tone();
   }
}

/*******************************
 * Initial
 *
 * This function performs all initializations of variables and registers.
 *******************************
 */
void Initial()
{
   OSCCON = 0b01100010;         // Use Fosc = 4 MHz (Fcpu = 1 MHz)
   ADCON1 = 0b00001111;         // RA0,1,2,...  digital
   TRISA = 0b00000000;          // Set I/O for PORTA
   TRISB = 0b01110100;          // Set I/O for PORTB
   TRISC = 0b10000000;          // Set I/O for PORTC
   TRISD = 0b00000000;          // Set I/O for PORTD
   TRISE = 0b00000000;          // Set I/O for PORTE
   PORTA = 0;                   // Set initial state for all outputs
   PORTB = 0;
   PORTC = 0;
   PORTD = 0;
   PORTE = 0;
   Delay(50000);                // Pause for half a second
   RCONbits.SBOREN = 0;         // Now disable brown-out reset
   ALIVECNT = 197;              // Blink immediately
   PORTAbits.RA7 = 1;           // Power pullup resistor for RPG
   Nop();
   OLDPORTB = PORTB;            // Initialize OLDPORTB
   PORTAbits.RA7 = 0;           // Power down pullup resistor for RPG

   NOTENUM = 7;                 // Initial note equals C = 1046 Hz
   romPtr = Notes;              // Point to Notes table
   HALFPERIOD = *romPtr;  	// Freq = 880 Hz, initially
   CCP1CON = 0b00000010;        // Toggle CCP1 pin on compare
   CCPR1 = HALFPERIOD;
   PIR1bits.CCP1IF = 0;         // Clear compare flag
   TMR1H = 0;                   // Clear Timer1
   TMR1L = 0;
   T1CON = 0b10000001;          // Clock Timer1 from Fcpu = 1 MHz
}

/*******************************
 * RPG
 *
 * Respond to rising and falling edges on INT2 input from RPG.
 *******************************
 */
void RPG()
{
   unsigned char TEMP;
   unsigned char newB;
   DELRPG = 0;
   PORTAbits.RA7 = 1;           // Power pullup resistor for RPG
   Nop();
   TEMP = PORTB;
   newB = PORTB;
   PORTAbits.RA7 = 0;           // Power down pullup resistor for RPG
   TEMP = OLDPORTB ^ TEMP;
   TEMP = TEMP & 0b00110000;
   if (TEMP != 0)  		// change?
   {
      TEMP = OLDPORTB >> 1;
      TEMP = newB ^ TEMP;
      TEMP = TEMP & 0b00010000;
      if (TEMP != 0)
      {
         DELRPG--;		//CCW
      }
      else
      {
         DELRPG++;		//CW
      }
   }
   OLDPORTB = newB;
}

/*******************************
 * Tone()
 *
 * This function waits for TMR1 = CCPR1.
 * Then it adds HALFPERIOD to CCPR1 and clears CCP1IF flag.
 * Then it adds DELRPG*16 to HALFPERIOD.
 */
void Tone()
{
   while (!PIR1bits.CCP1IF);    // Wait for flag to set
   CCPR1 += HALFPERIOD;         // Increase CCPR1 by HALFPERIOD
   PIR1bits.CCP1IF = 0;         // Then clear flag

   NOTENUM += DELRPG; 		// Update which note to play
   if (NOTENUM == -1) NOTENUM = 0;
   if (NOTENUM == 15) NOTENUM = 14;
   HALFPERIOD = Notes[NOTENUM];
}