Question

Please comment and or provide information on what each function or line does within the following code. The code is a Arduino Atmega C programming language code which which creates a piano keyboard outputting different frequencies per. I would really appreciate a detailedf explanation on what each function and line does as I am a beginner and need to use this within lab.

volatile unsigned char *TCCR1A = (unsigned char *) 0x80; /* Address location for Timer/Counter Control Register A. */
volatile unsigned char *TCCR1B = (unsigned char *) 0x81; /* Address location for Timer/Counter Control Register B. */
volatile unsigned char *TCCR1C = (unsigned char *) 0x82; /* Address location for Timer/Counter Control Register C. */
volatile unsigned char *TIMSK1 = (unsigned char *) 0x6F; /* Address location for Timer/Counter 1 Interrupt Mask Register. */
volatile unsigned int *TCNT1 = (unsigned int *) 0x84; /* Address location for Timer/Counter 1L (lower 8-bits). */
volatile unsigned char *TIFR1 = (unsigned char *) 0x36; /* Address location for Timer/Counter 1 Interrupt Flag Register. */
volatile unsigned char *PORT_B = (unsigned char *) 0x25; /* Address location for PORT B. */
volatile unsigned char *PORT_DDRB = (unsigned char *) 0x24; /* Address location for PORT B Data Direction Register. */
unsigned int Value[13] = {18181, 17167, 16194, 15286, 14440, 13628, 12820, 12139, 11461, 10810, 10204, 9626, 0};
unsigned char Input[13] = {'a', 'A', 'b', 'c', 'C', 'd', 'D', 'e', 'f', 'F', 'g', 'G', 'q'};
volatile unsigned int note;

void myTimer(unsigned int note);

byte byteRead;

void setup()
{
  
Serial.begin(9600);

*TCNT1 &= 0;

*TCCR1A &= 0;
*TCCR1B &= 0;
*TCCR1C &= 0;
*TIMSK1 &= 0;
  
*PORT_DDRB |= 0x40;
  
}

void loop()
{

  
if (Serial.available())
{
  
byteRead = Serial.read();
  

Serial.write(byteRead);
}

  
for(int i = 0; i<13; i++){
if(Input[i] == byteRead){
note = Value [i];
}
}
  
  
*PORT_B |= 0x40;
myTimer(note);
*PORT_B &= 0xBF;
myTimer(note);
  

}

void myTimer(unsigned int note)
{
*TCCR1B &= 0xF8;
/* Load Timer/Counter 1 and delay for half of the period. */
*TCNT1 = unsigned int (65536 - note);
/* Set the precsaler to 1, Timer 1, NORMAL mode. */
*TCCR1B |= 0x01;
/* Set PORT_B HIGH. */
*PORT_B |= 0x40;
/* Wait for TIFR1 overflow flag bit to be set. */
while ((*TIFR1 & 0x01) == 0);
/* Turn off the Timer after getting delay. */
*TCCR1B &= 0xF8;
/* Clear the flag bit on TIFR1 for next use. */
*TIFR1 |= 0x01;
  
  
}

Answer 1

Serial.begin(9600): this line is for selection of baud rate. Here it selects baud rate of 9600 means 9600 bits information transfer per sec.

*TCNT1 &= 0;

*TCCR1A &= 0;
*TCCR1B &= 0;
*TCCR1C &= 0;
*TIMSK1 &= 0;(These lines are for assigning off condition to the arduino ports.)

byteRead = Serial.read(); This line is for taking input signals.

if(Input[i] == byteRead) : this will compare the value of input with byte entered.
note = Value [i]; Here if above condition will be true then note will get assigned value of value[i].