Atmega16 external interrupt programming example

Atmega16 has up to 21 interrupt sources. Here I will discuss only the external interrupt of this controller. External interrupt consist of three source sources:

1. INT0 - External interrupt request 0
2. INT1 - External interrupt request 1, and
3. INT2 - External interrupt request 2.

First I will show how to use INT0 source. It has four sense that determine whether the interrupt is triggering. It is the Interrupt Sense Control register bits of the MCU Control Register (MCUCR).

MCU Control Register (MCUCR)

 Interrupt Sense Control register bits

The General Interrupt Control Register (GICR) turn on and off these external interrupt source, including the INT0 source.

General Interrupt Control Register – GICR

They also have their corresponding interrupt flag in the General Interrupt Flag Control (GIFR).

General Interrupt Flag Control (GIFR)

There are three bit corresponding to INTF1, INTF0, and INTF2. These bits will be cleared after the Interrupt Service Routine (ISR) executed. Optionally the programmer can clear any flag by setting it. However it is uncommon from most of microcontrollers.

In C programming the interrupt is very easy to program that I will show it in this programming example.

In this example I use only the INT0 source. The interrupt sense is the falling edge of INT0, as I will select it in program. Each time the INT0 occurs, and output LED connects to PD7 will toggle.

Schematic Diagram

The source code is very simple. It contains a little lines of code.

/*
 * int0Example1.c
 *
 * Created: 5/27/2022 6:45:11 PM
 * Author : Admin
 */ 
 
#include <avr/io.h>
 
#include <avr/interrupt.h>
 
int main(void)
{
    //PortD output
	DDRD=0xFF;
	//RD2 input
	DDRD&=~(1<<2);
	//Turn on RD2
	PORTD|=(1<<2);
	//Select falling edge of INT0
	MCUCR|=(1<<ISC01);
	//Enable INT0 request
	GICR|=(1<<INT0);
	//Enable interrupt
	sei();
	//Clear Flag
	GIFR|=(1<<INTF0);
    while (1) 
    {
    }
}
 
//Interrupt Service Routine - ISR
ISR(INT0_vect){
	//Toggle PD7
	PORTD^=0x80;
}
 

Click here to download it source file.

A DIY USB Charger with LM1117MP Voltage Regulator

USB charging requires only a constant voltage of +5V DC, with constant current. The LM1117MP-5,0 linear voltage regulator is very popular due to its simplicity of circuit wiring. It outputs a +5V voltage, and 1A current. It has low drop down voltage.

A finished circuit soldering

It's constructed with about a dozen of components I have. The LM1117MP-5,0 is an SMD device, but soldering it on PCB is not difficult.

Circuit diagram

PCB Drawing

I used Proteus 8 to draw the schematic and PCB. 

Bottom copper pattern with non-mirror

Top silk mirror

Top copper mirror

Three-D view of this PCB design

Click here to download source file.

PWM Pulse Steering in PIC16F887

CCP1 can generate PWM signal up to 4 pins at the same time, by selecting CCP1M<3:2> = 11 and P1M<1:0> = 00. The Pulse Steering Control Register (PSTRCON) allow us to select any streering pin between P1A, P1B, P1C, and P1D.

 PSTRCON: PULSE STEERING CONTROL REGISTER

SIMPLIFIED STEERING BLOCK DIAGRAM

In this example, I use all PWM steering pins to generate the signal of 25% duty cycle.

void main() {
     TRISC=0x01;
     TRISD=0x00;
     OSCCON=0x70;
     CCP1CON=0x3C;
     PSTRCON=0x0F;             // steering output to P1<D:A>
     PR2=99;                   // Period is 50us
     CCPR1L=22;               // duty cycle is 25%
     T2CON=0x00;             // Timer2 Prescaler is 1:1
     TMR2=0;                   // clear timer 2
     T2CON.TMR2ON=1;          // Enable timer2
     PIR1.TMR2IF=0;             // clear flag
     while(PIR1.TMR2IF==0);     // wait until new cycles
}

I use simulator to test this program.

Program simulation

This system uses a 8MHz internal RC oscillator of PIC16F887.