MICROPROCESSOR PROJECT

Components provided are

Nerdkit- ATMEGA 168 MICROPROCESSOR
4*3 KEYPAD
MYLAR CONE SPEAKER
LM386N-1 LOW VOLTAGE 1W AMPLIFIER IC (DATASHEET)
10KΩ POTENTIOMETER FOR VOLUME ADJUSTMENT
Capacitor
a. Capacitor (473) 47 nF
b. Electrolytic Capacitors/Voltage: 220uF/25V
Resistors –2KΩ , 220 Ω , 100 Ω, 100 Ω
2 LED

software used is WinAVR-20100110 and code in assembler language.

SAMPLE PROGRAM CODE FOR INTERFACING WITH KEYPAD
uint8_t debg;

// PIN DEFINITIONS:
//
// PC0 — KEYPAD COL1 (left column)
// PC1 — KEYPAD COL2 (centre column)
// PC2 — KEYPAD COL3 (right column)
// PC3 — KEYPAD ROW1 (top row)
// PC4 — KEYPAD ROW2 (second row)
// PC5 — KEYPAD ROW3 (third row)
//
// NOTE: We have not connected bottom row
// because PC6 is being used as RESET input (tied high)

void keypad_init() {
// set ports to proper input and output
// enable pull up resistors for inputs

// Set the columns as ouput
// Set row pins to input mode
// Port C bit 0 and 1 and 2 as output (columns)
DDRC |= (1<<PC2) |(1<<PC1) |(1<<PC0) ;
DDRC &= ~(1<<PC3); // set PC3 as input
DDRC &= ~(1<<PC4); // set PC4 as input
DDRC &= ~(1<<PC5); // set PC5 as input

// turn on the internal resistors for the input pins
PORTC |= (1<<PC3); // turn on internal pull up resistor for PC3
PORTC |= (1<<PC4); // turn on internal pull up resistor for PC6
PORTC |= (1<<PC5); // turn on internal pull up resistor for PC7

// Set column output pins low, so input low if contact made
PORTC &= ~(1<<PC2 | 1<<PC1 | 1<<PC0 ); // set PC0, PC1 and PC2 low

} // END keypad_init

uint8_t keypressed() {
// checks to see if any key has been pressed
// sets columns to 0, and checks if any row goes low
// Returns a 1 (true) if a key has been pressed, 0 if not pressed

// Set column output pins low, so input low if contact made

uint8_t rowvl;
uint8_t kp;

PORTC &= ~(1<> 3);
rowvl&= (1<<PC2 | 1<<PC1 | 1<<PC0); // mask out other bits

kp = (rowvl != 7); // if 7, all high so no key

return kp;
}

char keypad_read(char lastchar) {
// read from keypad
// (assumes key has been pressed)
// returns keyval0..9
// takes in lastchar, and returns that if invalid read from keypad

uint8_t rowval;
char keych; // Initialise to $

keych = ‘$’;

PORTC |= ( (1<<PC2) | (1<<PC1)); // set other 2 high
PORTC &= ~(1<<PC0 ); // set PC0 low – check column 1
delay_us(10); // delay to allow signals to settle

// Read value from Pins on PortC
// Then shift right 3 to get pins3, 4 and 5 in first 3 bits
rowval= (PINC >> 3);
rowval&= (1<<PC2 | 1<<PC1 | 1<<PC0); // mask out other bits

switch(rowval) {
case 6: keych = ‘1’;
break;
case 5: keych = ‘4’;
break;
case 3: keych = ‘7’;
break;
default: keych = ‘$’;
break;
}

if (keych==’$’) { // if still not valid key
PORTC |= ( (1<<PC2) | (1<<PC0)); // set other 2 high
PORTC &= ~(1<<PC1 ); // set PC1 low – check column 2
delay_us(10); // delay to allow signals to settle

 // Read value from Pins on PortC

rowval= (PINC >> 3);
rowval&= (1<<PC2 | 1<<PC1 | 1<<PC0); // mask out other bits

 switch(rowval) {
 case 6: keych = '2';
          break;
 case 5: keych = '5';
         break;        
 case 3: keych = '8';
         break;
 default: keych = '$'; 
         break;     
 }

}

if (keych==’$’) { // if still not valid key
PORTC |= ( (1<<PC1) | (1<<PC0)); // set other 2 high
PORTC &= ~(1<<PC2 ); // set PC2 low – check column 3
delay_us(10); // delay to allow signals to settle

 // Read value from Pins on PortC

rowval= (PINC >> 3);
rowval&= (1<<PC2 | 1<<PC1 | 1<<PC0); // mask out other bits

 switch(rowval) {
 case 6: keych = '3';
          break;
 case 5: keych = '6';
         break;        
 case 3: keych = '9';
         break;
 default: keych = '$'; 
         break; 
 }

}

if (keych != ‘$’) { // if valid character
lastchar = keych; // update last char
}
return lastchar;

} // END keypad_read

void init_interrupts() {
// To set up the interrupts for the pin – PCINT1
// Enable the particular pin change interrupt – PC0
// Enable global interrupts

PCMSK0 = ( 1<<PCINT1 ) ;/* INSERT your own code here */ // Enable PCINT1 interrupt, and clear others

PCICR &= ~((1<<PCINT1) | (1<<PCINT2)) ;/* INSERT your own code here / // Disable PC Int 1 and PC Int 2 PCICR |= ( 1< INSERT your own code here */ // Enable PC Int 0
sei(); // Enable global interrupts

} // END init_interrupts

//
void init_switch_port() {
// Initialises Port B
// Turn GREEN LED ON and Red LED OFF
// Initialises Port B

DDRB &= ~(1<<PB1);

PORTB |= (1<<PB1);

DDRB |= (1<<PB3) | (1<<PB5);

PORTB |= (1<<PB3) |(1<<PB5); // PB1 set as input for switch

// PB3 and PB5 set as outputs for LEDs

PORTB &= ~(1<<PB3) ; // Turn GREEN LED ON and Red LED OFF
PORTB &= (1<<PB5) ;

} // END init_switch_port

ISR(PCINT0_vect) {
// This uses the predefined ISR function to create an ISR
// The compiler generates the initial and final code
// (including the RETI instruction)
// This will result in the following code being run when
// Interrupt PC0 (Pin change 0) happens
delay_ms(1); // delay to ‘debounce’ switch
PORTB ^= (1<<PB3) | (1<<PB5); // XOR bits 3 and 5 to toggle LEDs

} //End ISR PCINT0

int main() {

// variables declaration and initialisation
char keychar = ‘C’;
int8_t keynum;

debg = 0;

// start up the LCD
lcd_init();
lcd_home();

// initialise keypad, switch port
keypad_init();
init_switch_port();

// wait a bit then enable interrupts
delay_ms(1);
init_interrupts();

while(1) {

   // continuously check keypad
   // IF key is pressed then read and display character
   if (keypressed()) {
keychar = keypad_read(keychar); 
    }
    else {
    //do nothing for now
    }

lcd_home();
lcd_write_string(PSTR("Last Key pressed: "));

lcd_write_data(keychar);
lcd_write_string(PSTR("  "));

}
return 0;
}

Share this:

Leave a Reply Cancel reply