Difference between revisions of "AVR External Interrupts"
| Line 53: | Line 53: | ||
=Hook Up= | =Hook Up= | ||
=The Code= | =The Code= | ||
| − | + | <syntaxhighlight> | |
| + | #include<avr/io.h> | ||
| + | #include<avr/interrupt.h> | ||
| + | #include<util/delay.h> | ||
| + | #include "lcd.h" | ||
| + | |||
| + | volatile int cnt_zero,cnt_one; | ||
| + | |||
| + | ISR (INT0_vect) //External interrupt_zero ISR | ||
| + | { | ||
| + | cnt_zero++; | ||
| + | } | ||
| + | |||
| + | ISR (INT1_vect) //External interrupt_one ISR | ||
| + | { | ||
| + | cnt_one++; | ||
| + | |||
| + | } | ||
| + | |||
| + | int main() | ||
| + | { | ||
| + | DDRC=0xff; //Configure PORTC(Lcd databus) as output | ||
| + | DDRD=0xe0; //Configure INT0,INT1 as input and PORTD5-PORTD7(rs,rw,en) as output | ||
| + | |||
| + | LCD_SetUp(PB_0,PB_1,PB_2,P_NC,P_NC,P_NC,P_NC,PB_4,PB_5,PB_6,PB_7); | ||
| + | LCD_Init(2,16); | ||
| + | |||
| + | GICR=0xc0; //Enable External Interrupts INT0 and INT1 | ||
| + | MCUCR=0x08; //Configure INT0 active low level triggered and INT1 as falling edge | ||
| + | |||
| + | sei(); // Enable global interrupts by setting global interrupt enable bit in SREG | ||
| + | |||
| + | while(1) | ||
| + | { | ||
| + | LCD_Printf("EINT0:%4u\n",cnt_zero); | ||
| + | LCD_Printf("EINT1:%4u\n",cnt_one); | ||
| + | } | ||
| + | } | ||
| + | </syntaxhighlight> | ||
=Downloads= | =Downloads= | ||
Revision as of 17:20, 19 March 2016
We have looked at the basics of AVR Interrupts, now let us go ahead and use the External Interrupts feature on the AVR MCUs.
Steps to configure the Interrupts:
- Set Global Interrupt(I-bit) Enable bit in the AVR Status Register(SREG)
- Set INT1 and INT0 bits in the General Interrupt Control Register (GICR)
- Configure MCU Control Register (MCUCR) to select interrupt type.
- Handle the interrupt in the Interrupt Service Routine code.
Contents
The Registers
General Interrupt Control Register (GICR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| INT1 | INT0 | INT2 | - | - | - | IVSEL | IVCE |
MCU Control Register (MCUCR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| SE | SM2 | SM1 | SM0 | ISC11 | ISC10 | ISC01 | ISC00 |
| ISC01 | ISC00 | Description |
|---|---|---|
| 0 | 0 | The low level of INT0 generates an interrupt request. |
| 0 | 1 | Any logical change on INT0 generates an interrupt request. |
| 1 | 0 | The falling edge of INT0 generates an interrupt request. |
| 1 | 1 | The rising edge of INT0 generates an interrupt request. |
General Interrupt Flag Register(GIFR)
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|
| INTF1 | INTF0 | INTF2 | - | - | - | - | - |
We will connect two switches to the two interrupt pins and show the status on a LCD. The connections are shown in the image below.
Hook Up
The Code
#include<avr/io.h> #include<avr/interrupt.h> #include<util/delay.h> #include "lcd.h" volatile int cnt_zero,cnt_one; ISR (INT0_vect) //External interrupt_zero ISR { cnt_zero++; } ISR (INT1_vect) //External interrupt_one ISR { cnt_one++; } int main() { DDRC=0xff; //Configure PORTC(Lcd databus) as output DDRD=0xe0; //Configure INT0,INT1 as input and PORTD5-PORTD7(rs,rw,en) as output LCD_SetUp(PB_0,PB_1,PB_2,P_NC,P_NC,P_NC,P_NC,PB_4,PB_5,PB_6,PB_7); LCD_Init(2,16); GICR=0xc0; //Enable External Interrupts INT0 and INT1 MCUCR=0x08; //Configure INT0 active low level triggered and INT1 as falling edge sei(); // Enable global interrupts by setting global interrupt enable bit in SREG while(1) { LCD_Printf("EINT0:%4u\n",cnt_zero); LCD_Printf("EINT1:%4u\n",cnt_one); } }