This repo contains libraries for AVR ATmega 2560 & similar micro-controllers. It contains function names same as that used in Arduino IDE
io.h is the main library containing all the basic functions for ATmega2560 microcontroller INDEX: 1]pulseIn() 2]LCD
1]pulseIn():
FUNCTIONS:
- unsigned long pulseIn(); This function reads a pulse (either HIGH or LOW) on a pin. For example, if value is HIGH, pulse_In() waits for the pin to go from LOW to HIGH, starts timing, then waits for the pin to go LOW and stops timing. Returns the length of the pulse in microseconds or gives up and returns 0 if no complete pulse was received within the timeout.
SYNTAX: unsigned long pulseIn (volatile uint8_t bitno, uint8_t stateMask);
PARAMETERS: • bitno: The pin number on which you want to read the pulse. (int) • stateMask: type of pulse to read: either 1(for high) or 0(for low). (int)
-
unsigned long microsecondsToInches(); • There are 73.746 microseconds per inch (i.e. sound travels at 1130 feet per second).This gives the distance travelled by the ping, outbound and return, so we divide by 2 to get the distance of the obstacle.
Formula: microseconds1*0.00669/ 2 SYNTAX: unsigned long microsecondsToInches(unsigned long microseconds1)
-
unsigned long microsecondsToCentimeters(); • The speed of sound is 340 m/s or 29 microseconds per centimetre. The ping travels out and back, so to find the distance of the object we take half of the distance travelled.
Formula: microseconds*0.17/ 2 SYNTAX: unsigned long microsecondsToCentimeters(unsigned long microseconds)
EXAMPLE CODE: #include <avr/io.h> #include <util/delay.h> #include <pulseIn.h>
int main() { DDRC=0b11111111; DDRD=0b00000000; while(1) { // establish variables for duration of the ping, and the distance result // in inches and centimeters: unsigned long duration, inches, cm;
// The PING))) is triggered by a HIGH pulse of 2 or more microseconds. // Give a short LOW pulse beforehand to ensure a clean HIGH pulse: //trig 10 PORTC=(1<<pingPin); _delay_us(2); PORTC=(1<<pingPin); _delay_us(5); PORTC=(1<<pingPin);
// The same pin is used to read the signal from the PING))): a HIGH pulse // whose duration is the time (in microseconds) from the sending of the ping // to the reception of its echo off of an object. //echo11 duration = pulseIn(Pin,1);
// convert the time into a distance
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);
PORTB=0;
if(cm<10)
{
PORTB=0b00000001;
}
if(cm>=10||cm<20)
{
PORTB=0b00000010;
}
if(cm>=20||cm<30)
{
PORTB=0b00000100;
}
else if(cm>=30)
{
PORTB=0b00001000;
}
}
}
2]LCD:
FUNCTIONS: 1. Lcd8_Init () & Lcd4_Init (): These functions will initialize the 16×2 LCD module connected to the microcontroller pins defined by the following constants. 2. Lcd8_Clear() & Lcd4_Clear() : Calling these functions will clear the 16×2 LCD display screen when interfaced with 8 bit and 4 bit mode respectively. 3. Lcd8_SetCursor() & Lcd4_SetCursor() : These function will set the cursor position on the LCD screen by specifying its row and column. By using these functions we can change the position of character and string displayed by the following functions. 4. Lcd8_WriteChar() & Lcd4_WriteChar() : These functions will write a single character to the LCD screen and the cursor position will be incremented by one. 5. Lcd8_WriteString() & Lcd8_WriteString() : These function will write string or text to the LCD screen and the cursor positon will be incremented by length of the string plus one. 6. Lcd8_ShiftLeft() & Lcd4_ShiftLeft() : This function will shift data in the LCD display without changing data in the display RAM. 7. Lcd8_ShiftRight() & Lcd8_ShiftRight() : This function will shift data in the LCD display without changing data in the display RAM. 8. For Pin change • Change Lcd4_Port(data) and Lcd8_Port(data) to PORTD = data • Change pinChange(EN,1) to PORTC |= (1<<PC7) • Change pinChange(EN,0) to PORTC &= ~(1<<PC7) • Change pinChange(RS,1) to PORTB |= (1<<PB6) • Change pinChange(RS,0) to PORTC &= ~(1<<PC6) EXAMPLE CODE: // Defining pins for LCD #define D4 eS_PORTD4 #define D5 eS_PORTD5 #define D6 eS_PORTD6 #define D7 eS_PORTD7 #define RS eS_PORTC6 #define EN eS_PORTC7 //Including standard libs #include <avr/io.h> #define F_CPU 8000000UL #include <util/delay.h> #include <avr/interrupt.h> #include <stdlib.h> #include "lcd.h" // Defining pins #define trig PB0 //Output pin for sending trigger pulse #define echo 2 //Input pin for receiving distance proportional pulse
int time=0;
void set_interrupt() { GICR |= (1<<INT0); //Enable external interrupts MCUCR |= (1<<ISC00); //Trigger interrupt on logical change MCUCR &= ~(1<<ISC01); sei(); //Enable global interrupts or SREG |= (1<<I) }
void init_timer() { TCCR1B = (1<<CS11); // Initialize timer1 with prescaler of 8 TCNT1 = 0; }
void trigger() { PORTB &= ~(1<<trig); _delay_us(2); PORTB |= (1<<trig); _delay_us(12); PORTB &= ~(1<<trig); _delay_us(2); }
ISR(INT0_vect) { if(TCNT1 == 0) { init_timer(); } else { time = TCNT1; TCNT1 = 0; TCCR1B = 0x00; } }
int main(void) { DDRB |= (1<<trig); //Setting trigger pin as output DDRC |= (0b11100000); //Setting enable and RS pin as output DDRD &= ~(1<<echo); //Setting echo pin as input DDRD |= (0b11110000); //Setting LCD data pins as output set_interrupt(); Lcd4_Init(); int dist = 0; char a[10]; while (1) { trigger(); dist = time/58; itoa(dist, a, 10); if(dist>400) { Lcd4_Set_Cursor(1,1); Lcd4_Write_String("No object found"); } else { Lcd4_Set_Cursor(1,1); Lcd4_Write_String("Distance : "); Lcd4_Write_String(a); }
_delay_ms(1000);
Lcd4_Clear();
}
}