ARM HOW-TO GUIDE Interfacing Interrupts with LPC2148 · PDF file06/12/2014 · C Program to interface Ext-Interrupt using LPC2148 ... file into your microcontroller IC LPC2148 through

ARM HOW-TO GUIDE

Interfacing Interrupts

with LPC2148 ARM

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Contents at a Glance

ARM7 LPC2148 Slicker Board ........................................... 3

External Interrupts .......................................................... 3

Interfacing External Interrupts ......................................... 4

Interfacing External Interrupts with LPC2148 ................... 5

Pin Assignment with LPC2148 .......................................... 5

Circuit Diagram to Interface Ext-Interrupt with LPC2148 ... 6

Source Code .................................................................... 6

C Program to interface Ext-Interrupt using LPC2148 ......... 7

Testing the External Interrupts with LPC2148 ................. 10

General Information ...................................................... 11



ARM7 LPC2148 Slicker Board

The ARM7 LPC2148 Slicker board is specifically

designed to help students to master the required skills in

the area of embedded systems. The kit is designed in such

way that all the possible features of the microcontroller will

be easily used by the students. The kit supports in system

programming (ISP) which is done through serial port.

NXP’s ARM7 (LPC2148), ARM Slicker Kit is proposed to

smooth the progress of developing and debugging of

various designs encompassing of High speed 32-bit

Microcontrollers.

External Interrupts

An interrupt caused by an external source such as the

computer operator, external sensor or monitoring device,

or another computer. Interrupts are special events that

require immediate attention.



Interfacing External Interrupts

Fig. 1 shows how to interface the External Interrupt to

microcontroller. Interrupts cause the processor to cease the

running task to serve a special task for which the interrupt

event had occurred. After the special task is over, the

processor resumes performing the original task.

The processor can also serve these events by polling

method. But polling is an inefficient technique as compared

to interrupts. In the polling method, the processor has to

continuously wait for the event signal. Thus it always

remains busy using extra resources.



Fig. 1 Interfacing External Interrupts to Microcontroller

Interfacing External Interrupts with LPC2148

We now want to display some messages in PC when

occur an external interrupt signal in LPC2148 Slicker Board.

The Interrupt signal is occurred by using switches. When the

switch is pressed to LOW, then the external interrupt is

occurred.

The Vectored Interrupt Controller (VIC) takes 32

interrupt request inputs and programmable assigns them

into 3 categories, FIQ, vectored IRQ, and non-vectored IRQ.

The ARM7 LPC2148 Slicker board has two numbers of

External Interrupts, connected with I/O Port lines (P0.14 &

P0.15) as switches.

Pin Assignment with LPC2148

Interrupts LPC2148 Lines Interrupts



Circuit Diagram to Interface Ext-Interrupt with LPC2148

Source Code

Tact

ile

Swit

ch

DS1

30

7 SW5 – (INT1) P0.14

SW6– (INT2) P0.15

ARM7

INTR

3.3V

C68

22pf

C69

22pf

X29

12MHz

LPC2148

U16

VSS16 V

DD

A7

VSS218

VD

D3

23

VSS325

VD

D2

43

VSS442

VR

EF

63

XT

AL1

62

XT

AL2

61

VSSA59

VD

D1

51

VSS550

P0.1545

P0.1441

C9

100n

C10

100n

R622K

SW6

INT2

R522K

SW5

INT1

3V3

INTERRUPTS

3V3



The Interfacing External Interrupt with LPC2148

program is very simple and straight forward, that accessed

by using switches. When the external interrupts occurring,

some messages are displayed in PC through serial port at

9600 baud rate. The C programs are written in Keil

software.

C Program to interface Ext-Interrupt using LPC2148 ***************************************************************************************

Title : Program to interface an external Interrupt ***************************************************************************************

#include<LPC214x.h> // Define LPC2148 Header File

#include <stdio.h>

int volatile EINT1 = 0;

int volatile EINT2 = 0;

void ExtInt_Serve1(void)__irq;

void ExtInt_Serve2(void)__irq;

void ExtInt_Serve1(void)__irq

{

++EINT1;

EXTINT |= 2;

VICVectAddr = 1;

}

void ExtInt_Serve2(void)__irq

{

++EINT2;



EXTINT |= 4;

VICVectAddr = 0;

}

void main(void)

{

Serial_Init();

ExtInt_Init1(); //Initialize Interrupt 1

ExtInt_Init2(); //Initialize Interrupt 2

putchar(0x0C);

printf ("***************** External Interrupt

Demo ***************************\n\n\r");

DelayMs(100);

printf (">>> Press Interrupt Keys SW2(INT1) and

SW3(INT2) for Output... \n\n\n\r");

DelayMs(100);

while(1)

{

DelayMs(500);

printf("INT1 Generated : %d | INT2 Generated

: %d \r", EINT1, EINT2);

DelayMs(500);

}

}

void ExtInt_Init2(void)

{

EXTMODE |= 4; //Edge sensitive mode on EINT2

EXTPOLAR = 0; //Falling Edge Sensitive

PINSEL0 |= 0x80000000; //Enable EINT2 on P0.15

VICVectCntl1 = 0x20 | 16; // 16 is index of EINT2



VICVectAddr1 = (unsigned long) ExtInt_Serve2;

VICIntEnable |= 1<<16; //Enable EINT2

}

void ExtInt_Init1(void)

{

EXTMODE |= 2; //Edge sensitive mode on EINT1

EXTPOLAR = 0; //Falling Edge Sensitive

PINSEL0 |= 0x20000000; //Enable EINT2 on P0.14

VICVectCntl0 = 0x20 | 15; //15 is index of EINT1

VICVectAddr0 = (unsigned long) ExtInt_Serve1;

VICIntEnable |= 1<<15; //Enable EINT1

}

void Serial_Init(void)

{

PINSEL0 |= 0X00000005; //Enable Txd0 and Rxd0

U0LCR = 0x00000083; //8-bit data,1-stop bit

U0DLL = 0x00000061; //XTAL = 12MHz

U0LCR = 0x00000003; //DLAB = 0;

}

void DelayMs(unsigned int count)

{

unsigned int i,j;

for(i=0;i<count;i++)

{

for(j=0;j<1000;j++);

}

}

To compile the above C code you need the KEIL

software. They must be properly set up and a project with



correct settings must be created in order to compile the

code. To compile the above code, the C file must be added

to the project.

In KEIL, you want to develop or debug the project

without any hardware setup. You must compile the code for

generating HEX file. In debugging Mode, you want to check

the port output without LPC2148 Slicker Board.

The Flash Magic software is used to download the hex

file into your microcontroller IC LPC2148 through UART0.

Testing the External Interrupts with LPC2148

Give +3.3V power supply to LPC2148 Slicker Board; the

serial cable is connected between the LPC2148 Slicker

Board and PC. Open the Hyper Terminal screen, select

which port you are using and set the default settings. Now

the screen should show which external interrupt is selected.

When you pressed the external interrupt key, the

screen should update which interrupt is now pressed. The



external Interrupts are controlled by using switches. If any

data is not coming in Hyper Terminal, then you just check

the serial cable is working or not. Otherwise you just check

the code with debugging mode in KEIL. If you want to see

more details about debugging just see the videos in below

link.

How to Create & Debug a Project in KEIL.

General Information

For proper working use the components of exact values

as shown in Circuit file. Wherever possible use new

components.

Solder everything in a clean way. A major problem

arises due to improper soldering, solder jumps and

loose joints.

Use the exact value crystal shown in schematic.

More instructions are available in following articles,

Interfacing UART with LPC2148 Microcontroller.

http://youtu.be/EzOCple4POk

http://www.pantechsolutions.net/index.php?option=com_k2&view=item&layout=item&id=665&virtuemart_category_id=1&Itemid=19



Interfacing Keys with LPC2148 Microcontroller.

User Manual of LPC2148 Slicker Board.

Tutorial of how to create & Debug a project in KEIL.






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ARM HOW-TO GUIDE Interfacing Interrupts with LPC2148 · PDF file06/12/2014 · C Program to interface Ext-Interrupt using LPC2148 ... file into your microcontroller IC LPC2148 through