Electronic Engineering Laboratory IV BEE31101 …fkee.uthm.edu.my/images/docs/labsheet/3/BEE31101/BEE...Electronic Engineering Laboratory IV (BEE31101) Lab 1: Introduction to ARM M3

Electronic Engineering Laboratory IV

BEE31101

Instruction Sheet

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Lab No. 4

Lab Title Introduction to ARM M3 Microcontroller (LPC1768)

Semester 02

Session 2019/20

Lab Durations 2 Hours

Independent Studies 1 Hour

Electronic Engineering Laboratory IV (BEE31101) Lab 1: Introduction to ARM M3 Microcontroller (LPC1768)

ii

FKEE, Sem02 Session 2019/20

Table of Content

Table of Content ii

1.0 Outcomes 1

2.0 Guidelines 1

3.0 Pre-Lab (5%) 2

4.0 Procedures Error! Bookmark not defined.

Overview 3

Example 1 Error! Bookmark not defined.

Example 2 3

5.0 Lab Activities (40%)

Lab Activity 1 Error! Bookmark not defined.

Lab Activity 2 Error! Bookmark not defined.

5.0 Observations (15%) 12

6.0 Questions (15%) 12

7.0 References Error! Bookmark not defined.


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1.0 Outcomes

After completing this module, student should be able to:

(1) Students will be able to write a program to configure the I/O pins based on the

microcontroller’s memory map.

(2) Students will be able to write a program for simple input/output operations using mbed

API

2.0 Instructions

1. Grouping: Lab group is not predetermine and consists with at most two team members.

2. Pre-Lab: Must be handwritten and submitted to the instructor at the beginning of lab session.

Verified by the instructor and returned to the students at the end of lab session. The verified

pre-lab will be attached with the final report for submission.

3. Lab Activities: All lab activities such as sample code, examples and lab assignments must

be held in the respective lab location and completed within the given times.

4. Demonstration: Student must demonstrate the successful sample code, examples and lab

assignments to the respective instructor. Verification only will be given upon completion of all

lab activities and initialized by the instructor on the cover page.

5. Report Organization: Report must be organized according to given report template.

6. Appendix: Handwritten source code with detail description of each command for lab

activities. Marks for lab activities are given based on attachment of the appendix. Printed

source code is required only as an attachment of lab activities.

7. Report Submission: Report must be received by respective technical staff (at respective

lab) before 4.00pm; not later than three (3) days upon completion of lab session.


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3.0 Pre-Lab (5%)

1. Explain memory mapped I/O in microprocessor/microcontroller.

(2 marks)

2. The initialization section of a certain program reads:

FIO0DIR0=0xF0;

FIO2DIR2=0x02;

Explain the settings that have been made.

(3 marks)

3. Explain the Application Programming Interface (API) in embedded system development.

(2 marks)


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4.0 Guidelines

Overview

Memory mapped I/O is the method of performing input and output between the CPU and

peripheral devices in a microprocessor system. It uses the same address space to address

both memory and I/O devices. The memory and registers of the I/O devices are mapped

to (associated with) address values. When an address is accessed by the CPU, it may

refer to a portion of physical RAM, or it can instead refer to memory of the I/O device.

Thus, the CPU instructions used to access the memory can also be used for accessing

devices. Figure 1.1 shows the memory map of the NXP LPC1768 microcontroller. For

example, the general purpose I/O (GPIO) is mapped to the memory addresses between

0x2009C000 to 0x2009FFFF. Meanwhile, the analog to digital converter (ADC) is mapped

to the memory addresses between to 0x40034000 to 0x40037FFF. In this lab, we will

configure the GPIO of the LPC1768 for a simple I/O operation.

Figure 1.1: Memory map of the LPC1768 microcontroller

General Purpose Input/Output (GPIO)


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The LPC1768 has five 32-bit digital I/O ports (Port 0, 1, 2, 3 and 4). However, not all bits

are physically implemented (has physical connection to the I/O pin). For example, Port 0

has 32-bit I/O port, but Pins 12, 13, 14, and 31 of this port are not available. Figure 1.2

shows the I/O posts of the LPC1768 microcontroller. Note that, the grey bits indicate the

pins are not available.

Figure 1.2: The LPC1768 ports

It is possible to set each port pin as an input or as an output. Each port has a 32-bit

register that controls the direction of each of its pins. These are called the FIODIR

registers. To specify which port the register relates to, the port number is embedded within

the register name, for example, FIO0DIR is the direction register for Port 0. Each bit in this

register then controls the corresponding bit in the I/O port, for example bit 0 in the direction

register controls bit 0 in the port. If the bit in the direction register is set to 1, then that port

pin is configured as an output; if the bit is set to 0, the pin is configured as an input.

It is sometimes more convenient not to work with the full 32-bit direction register,

especially when we might just be thinking of one or two bits within the register. For this

reason, it is also possible to access any of the bytes within the larger register, as single-

byte registers (8-bit). These registers have a number code at their end. For example,

FIO2DIR0 is byte 0 of the Port 2 direction register. A second set of registers, called FIOPIN,

holds the data value of the microcontroller’s pins, whether they have been set as input or

output. If a port bit has been set as an output, then writing to its corresponding bit in its


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FIOPIN register will control the logic value placed on that pin. If the pin has been set as

input, then reading from that bit will tell you the logic value asserted at the pin. Example in

Figure 1.3 shows how to configure the lower 4-bit of the Port 0, Byte 0 as the output while

the upper 4-bit as the input. Figure 1.4 shows the port and its associated pin on the

LPC1768 microcontroller.

Figure 1.3: Example of port configurations


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Figure 1.4: Port and its associated pin on the LPC1768

Figure 1.5 and 1.6 show the addresses of the FIODIR and FIOPIN respectively.


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Figure 1.5: Fast GPIO port Direction control byte and half-word accessible

register description


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Figure 1.6: Fast GPIO port Pin value register byte and half-word accessible

register description

Program Example 1: Sets up a digital output pin using control registers, and

flashes an led.

Figure 1: Analog inputs of the mbed LPC1678 microcontroller


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Listing 1.1: Example program for blinking the LED1 on the LPC1768 microcontroller

5.0 Lab Activities (40%)

Lab Assignment 1:

Modify the program in Listing 1.1 to blink the LED2 and LED3 on the LPC1768

microcontroller.

Introduction to the mbed microcontroller

#include "mbed.h"

// function prototypes

void delay(void);

//Define addresses of digital i/o control registers, as pointers to

volatile data

#define FIO1DIR2 (*(volatile unsigned char *)(0x2009C022))

#define FIO1PIN2 (*(volatile unsigned char *)(0x2009C036))

int main() {

FIO1DIR2=0xFF; // set port 2, lowest byte to output

FIO1PIN2=0x00;

while(1) {

FIO1PIN2 = 0x04; // OR bit 0 with 1 to set pin high

Delay();

FIO1PIN2 = 0x00; // AND bit 0 with 0 to set pin low

Delay();

}

}

//delay function

void delay(void){

int j; //loop variable j

for (j=0;j<1000000;j++) {

j++;//waste time

}

}


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The mbed takes a microcontroller (LPC1678) surrounds it with some very useful support

circuitry. It places this on a conveniently sized little printed circuit board (PCB) and

supports it with an online compiler, program library and handbook. This gives a complete

embedded system development environment, allowing users to develop and prototype

embedded systems simply, efficiently and rapidly. Fast prototyping is one of the key

features of the mbed approach. The mbed takes the form of a 2 inch by 1 inch (53 mm by

26 mm) PCB, with 40 pins arranged in two rows of 20, with 0.1 inch spacing between the

pins. This spacing is a standard in many electronic components. Figure 1.7 shows the

mbed architecture.

The API (Application Programming Interface) is a set of function of subroutine definitions

that is used to help the application developers (or a programmers) to develop a program

faster and easier by providing the necessary building blocks and libraries. Figure 1.8

illustrates the concept of API in mbed microcontroller.


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Figure 1.8: The mbed API

The mbed Software Development Kit (SDK) is a C/C++ microcontroller software platform

relied upon by tens of thousands of developers to build projects fast. The mbed library is

made up of a set of utilities, which are all itemized in the mbed website Handbook

(www.mbed.org). In the second lab session, we will learn about how to interface the

LPC1678 microcontroller to the simple I/O devices (digital and analog) its associated APIs.

Digital Input and Output

Our first API is DigitalOut where it is used to configure and control a digital output pin. The

DigitalOut API component creates a C++ class, called DigitalOut. The class then has a set

of member functions as follows:

The first of these is a C++ constructor, which must have the same name as the class itself.

This can be used to create C++ objects. By using the DigitalOut constructor, we can create

C++ objects where we can then write to it and read from it, using the functions write( ) and

read( ). Listing 1.2 demonstrates the use of mbed API to produce an output as in the

program in Listing 1.1. Please visit to www.mbed.com for other mbed APIs.

http://www.mbed.org/

http://www.mbed.com/


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Listing 1.2: Example program for blinking the LED1 on the LPC1768 microcontroller

using the mbed API

Lab Assignment 2:

Repeat Lab Assignment 1 by using mbed API. (LED2 and LED3)

5.0 Observations (15%)

1. From Listing 1.1, discuss how 0.1s delay can be implemented using C programming.

(5 marks)

2. From Lab Assignment 2, write down simple command line to blinking the LED1, LED2 and

LED3 on the LPC1768 microcontroller using the mbed API.

(10 marks)

6.0 Questions (15%)

1. By referring to Figure below, without using the mbed API, write a C++ program to perform

the operation as follows: when sw1 is pressed, the LEDs will act as a binary counter. While

when sw2 is pressed, all the LEDs will turn off.

(15 mark)

#include "mbed.h"

DigitalOut myled(LED1);

int main() { //the function starts here

while (1) { //a continuous loop is created

myled = 1; //switch the led on, by setting the output to logic 1

wait(1); //wait 1 seconds

myled = 0; //switch the led off

wait(1); //wait 1 seconds

} //end of while loop

} //end of main function

Documents

Electronic Engineering Laboratory IV BEE31101 …fkee.uthm.edu.my/images/docs/labsheet/3/BEE31101/BEE...Electronic Engineering Laboratory IV (BEE31101) Lab 1: Introduction to ARM M3