Here is a functioning code, through Atmel Studio 6 on a Micro Controller Atmega3

ID: 3765564 • Letter: H

Question

Here is a functioning code, through Atmel Studio 6 on a Micro Controller Atmega328p

My reasoning for this question is to use the formula for the freq of Pwm in the data sheet provided on the atmel website. Use that to update the output compare register to change the frequency of 12 of the key inputs below.

#include <avr/io.h>
#include <util/delay.h>

#define FOSC 16000000 // 16 MHz Clock Speed
#define BAUD 9600
#define MYUBRR FOSC/16/BAUD-1

//CPU PIN   ------>       KEYPAD PIN ------>       TYPE           ------> ROW/COL
//------------------------------------------------------------------------------
//PINB0       ------>       PIN 4       ------>       OUTPUT from CPU   ------>   COL 4
//PINB1       ------>       PIN 3       ------>       OUTPUT from CPU   ------>   COL 3
//PINB2       ------>       PIN 2       ------>       OUTPUT from CPU   ------>   COL 2
//PINB3 ------>       PIN 1       ------>       OUTPUT from CPU   ------>   COL 1

//PINC3       ------>       PIN 8       ------>       INPUT with PU   ------>   ROW 4
//PINC2       ------>       PIN 7       ------>       INPUT with PU   ------>   ROW 3
//PINC1       ------>       PIN 6       ------>       INPUT with PU   ------>   ROW 2esssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss
//PINC0       ------>       PIN 5       ------>       INPUT with PU   ------>   ROW 1
//------------------------------------------------------------------------------

#define COL1       PINB3   //WRITE TO PORTS READ FROM PINS
#define COL2       PINB2
#define COL3       PINB1
#define COL4       PINB0
#define ROW4       PORTC3
#define ROW3       PORTC2
#define ROW2       PORTC1

//Function Prototypes
void InitUART(unsigned char);
void InitGPIO (void);
void USART_Transmit(unsigned char);
#define ROW1 PORTC0

#define DDRB_CFG 0x00 //0b 0000 0000 PINB[0:3] are inputs
#define DDRC_CFG 0x0F //0b 0000 1111 PINC[0:3] are outputs
#define PORTB_CFG 0x0F //0b 0000 1111 PULLUPS on PINB[0:3]

#define ROW1_LOW       0x0E //0b 0000 0111
#define ROW2_LOW       0x0D //0b 0000 1011
#define ROW3_LOW       0x0B //0b 0000 1101
#define ROW4_LOW       0x07 //0b 0000 1110

#define LOW 0
#define HIGH 1

unsigned char USART_Receive(void);
void SEND_KEYDATA(uint8_t);

void main(void)
{
   InitUART(MYUBRR);
   InitGPIO();

   unsigned char ROW_LOW[] = {ROW1_LOW, ROW2_LOW, ROW3_LOW, ROW4_LOW};

   while(1)
   {
       uint8_t i, j;

       for (i=0; i<=3; i++)
       {
           PORTC = ROW_LOW[i];
           j = i;
           SEND_KEYDATA(j);
       }
   }
   }

//*********************************************************************************************************************
//FUNCTIONS************************************************************************************************************
//*********************************************************************************************************************

//INITIALIZE UART
void InitUART( unsigned char ubrr)
{
   UBRR0H = (unsigned char)(ubrr>>8); // Set bits 8 to 11 in Baud Rate Register
   UBRR0L= (unsigned char)ubrr; //Set bits 0 to 7 in Baud Rate Register

   UCSR0B = (1<<TXEN0)|(1<<RXEN0); //write a 1 TXEN register to Enable Transmit and 1 to RXEN register to enable Receive

UCSR0C = (1<<UCSZ00)|(1<<UCSZ01); // Set asynchronous mode and frame format: 8data, 1stop bit
}

//INITIALIZE GPIO PINS
void InitGPIO(void)
{
   DDRB = DDRB_CFG;
   DDRC = DDRC_CFG;
   PORTB = PORTB_CFG;
}

//TRANSMIT DATA (TX PIN)
void USART_Transmit(unsigned char data)
{
while (!( UCSR0A & (1<<UDRE0)));
UDR0 = data;
}

//RECIEVE DATA (RX PIN)
unsigned char USART_Receive(void)
{
while (!(UCSR0A & (1<<RXC0)));
return UDR0;
}

void SEND_KEYDATA(uint8_t i)
{
   char key;
   if(!(PINB & (1<<COL1))) //check COL1
   {
       _delay_ms(500);
       if (i == 0) key = '1';
       else if (i == 1) key = '2';
       else if (i == 2) key = '3';
       else if (i == 3) key = 'A';
       USART_Transmit(key);
   }
   else if(!(PINB & (1<<COL2))) //check COL2
   {
       _delay_ms(500);
       if (i == 0) key = '4';
       else if (i == 1) key = '5';
       else if (i == 2) key = '6';
       else if (i == 3) key = 'B';
       USART_Transmit(key);
   }
   else if(!(PINB & (1<<COL3))) //check COL3
   {
       _delay_ms(500);
       if (i == 0) key = '7';
       else if (i == 1) key = '8';
       else if (i == 2) key = '9';
       else if (i == 3) key = 'C';
       USART_Transmit(key);
   }
   else if(!(PINB & (1<<COL4))) //check COL4
   {
       _delay_ms(500);
       if (i == 0) key = '*';
       else if (i == 1) key = '0';
       else if (i == 2) key = '#';
       else if (i == 3) key = 'D';
       USART_Transmit(key);
   }

Explanation / Answer

/*
Frequency of Pulse Width Modulation PWM :
PWM Period = { ( PR2) + 1 ] + 4 + TOSC

When PR2 = 255, and
FOSC = 40
then PWM Frequency = 1000000 / ( ( 256 ) * 4 * ( 25) ) = 39.06 Kilo Hertz

The following code can be used inside the program to calculate the PWM Frequency

double pwnFreq = 0.0;
int pr2 = 255, fosc = 40;
pwmFreq = 1000000 / ( ( 256 ) * 4 * (1000 / fosc ) );

// PWM can also be calculated by placing bit zero of the duty in the Least Significant Bit Register ( 4th bit)

CCPICON_4 = PW0

// and then the subsequent bits 5 will hold PW1, temp will hold PW shifted twice and so on

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Here is a functioning code, through Atmel Studio 6 on a Micro Controller Atmega3

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Here is a functioning code, through Atmel Studio 6 on a Micro Controller Atmega3

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