44-Pin Demo Board
User’s Guide
2006-2015 Microchip Technology Inc.
DS40001296C
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life support and/or safety applications is entirely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless Microchip from any and all damages, claims,
suits, or expenses resulting from such use. No licenses are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer,
LANCheck, MediaLB, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC,
SST, SST Logo, SuperFlash and UNI/O are registered
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
The Embedded Control Solutions Company and mTouch are
registered trademarks of Microchip Technology Incorporated
in the U.S.A.
Analog-for-the-Digital Age, BodyCom, chipKIT, chipKIT logo,
CodeGuard, dsPICDEM, dsPICDEM.net, ECAN, In-Circuit
Serial Programming, ICSP, Inter-Chip Connectivity, KleerNet,
KleerNet logo, MiWi, MPASM, MPF, MPLAB Certified logo,
MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code
Generation, PICDEM, PICDEM.net, PICkit, PICtail,
RightTouch logo, REAL ICE, SQI, Serial Quad I/O, Total
Endurance, TSHARC, USBCheck, VariSense, ViewSpan,
WiperLock, Wireless DNA, and ZENA are trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
Silicon Storage Technology is a registered trademark of
Microchip Technology Inc. in other countries.
GestIC is a registered trademarks of Microchip Technology
Germany II GmbH & Co. KG, a subsidiary of Microchip
Technology Inc., in other countries.
All other trademarks mentioned herein are property of their
respective companies.
© 2006-2015, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
ISBN: 978-1-63277-381-4
QUALITY MANAGEMENT SYSTEM
CERTIFIED BY DNV
== ISO/TS 16949 ==
DS40001296C-page 2
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Table of Contents
Preface ........................................................................................................................... 5
Chapter 1. 44-Pin Demo Board Overview
1.1 Introduction ................................................................................................... 11
1.2 Highlights ...................................................................................................... 11
1.3 Devices Supported by the 44-Pin Demo Board ............................................ 11
1.4 44-Pin Demo Board Overview ...................................................................... 12
1.5 Running the Default Demonstration ............................................................. 13
Chapter 2. PIC® Microcontroller Architectural Overview
2.1 Introduction ................................................................................................... 15
2.2 Memory Organization ................................................................................... 16
2.3 Programming ................................................................................................ 16
Chapter 3. 44-Pin Demo Board Lessons
3.1 Introduction ................................................................................................... 17
3.2 Program Flowchart ....................................................................................... 17
3.3 44-Pin Demo Board Lessons ....................................................................... 18
3.3.1 Lesson 1: Hello World (Light a LED) ......................................................... 18
3.3.2 Lesson 2: Blink (Delay Loop) .................................................................... 19
3.3.3 Lesson 3: Rotate (Move the LED) ............................................................. 20
3.3.4 Lesson 4: Analog-to-Digital ....................................................................... 21
3.3.5 Lesson 5: Variable Speed Rotate .............................................................. 23
3.3.6 Lesson 6: Reversible Variable Speed Rotate ............................................ 24
3.3.7 Lesson 7: Interrupt Priorities ..................................................................... 25
3.4 Lessons Not Included ................................................................................... 26
3.5 MPLAB® Code Configurator (MCC) ............................................................. 26
Appendix A. Hardware Schematics
A.1 Introduction .................................................................................................. 29
Worldwide Sales and Service .................................................................................... 32
2006-2015 Microchip Technology Inc.
DS40001296C-page 3
44-Pin Demo Board User’s Guide
NOTES:
DS40001296C-page 4
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Preface
NOTICE TO CUSTOMERS
All documentation becomes dated, and this manual is no exception. Microchip tools and
documentation are constantly evolving to meet customer needs, so some actual dialogs
and/or tool descriptions may differ from those in this document. Please refer to our web site
(www.microchip.com) to obtain the latest documentation available.
Documents are identified with a “DS” number. This number is located on the bottom of each
page, in front of the page number. The numbering convention for the DS number is
“DSXXXXXA”, where “XXXXX” is the document number and “A” is the revision level of the
document.
For the most up-to-date information on development tools, see the MPLAB® IDE online help.
Select the Help menu, and then Topics to open a list of available online help files.
INTRODUCTION
This chapter contains general information that will be useful to know before using the
44-Pin Demo Board. Items discussed in this chapter include:
•
•
•
•
•
•
•
•
Document Layout
Conventions Used in this Guide
Warranty Registration
Recommended Reading
The Microchip Web Site
Development Systems Customer Change Notification Service
Customer Support
Revision History
DOCUMENT LAYOUT
This document describes how to use the 44-Pin Demo Board as a development tool to
emulate and debug firmware on a target board. The document is organized as follows:
• Chapter 1. “44-Pin Demo Board Overview” – This chapter provides an
overview of the 44-Pin Demo Board for Microchip’s 44-pin Thin Quad Flatpack
(TQFP) PIC® microcontroller units (MCU).
• Chapter 2. “PIC®Microcontroller Architectural Overview”” – This chapter
provides an overview of the PIC microcontroller architecture.
• Chapter 3. “44-Pin Demo Board Lessons” – This chapter provides lessons that
introduce mid-range PIC MCU assembly instructions and cover basic 44-Pin
Demo Board features.
• Appendix A. “Hardware Schematics” – The appendix illustrates the 44-Pin
Demo Board hardware schematic diagram, PCB layout and bill of materials
(BOM).
2006-2015 Microchip Technology Inc.
DS40001296C-page 5
44-Pin Demo Board User’s Guide
CONVENTIONS USED IN THIS GUIDE
This manual uses the following documentation conventions:
DOCUMENTATION CONVENTIONS
Description
Arial font:
Italic characters
Initial caps
Quotes
Underlined, italic text with
right angle bracket
Bold characters
N‘Rnnnn
Text in angle brackets < >
Courier New font:
Plain Courier New
Represents
Examples
Referenced books
Emphasized text
A window
A dialog
A menu selection
A field name in a window or
dialog
A menu path
MPLAB® IDE User’s Guide
...is the only compiler...
the Output window
the Settings dialog
select Enable Programmer
“Save project before build”
A dialog button
A tab
A number in verilog format,
where N is the total number of
digits, R is the radix and n is a
digit.
A key on the keyboard
Click OK
Click the Power tab
4‘b0010, 2‘hF1
Italic Courier New
Sample source code
Filenames
File paths
Keywords
Command-line options
Bit values
Constants
A variable argument
Square brackets [ ]
Optional arguments
Curly brackets and pipe
character: { | }
Ellipses...
Choice of mutually exclusive
arguments; an OR selection
Replaces repeated text
Represents code supplied by
user
DS40001296C-page 6
File>Save
Press <Enter>, <F1>
#define START
autoexec.bat
c:\mcc18\h
_asm, _endasm, static
-Opa+, -Opa0, 1
0xFF, ‘A’
file.o, where file can be
any valid filename
mcc18 [options] file
[options]
errorlevel {0|1}
var_name [,
var_name...]
void main (void)
{ ...
}
2006-2015 Microchip Technology Inc.
Preface
WARRANTY REGISTRATION
Please complete the enclosed Warranty Registration Card and mail it promptly.
Sending in the Warranty Registration Card entitles users to receive new product
updates. Interim software releases are available at the Microchip web site.
RECOMMENDED READING
This user’s guide describes how to use the 44-Pin Demo Board. Other useful
documents are listed below. The following Microchip documents are available and
recommended as supplemental reference resources.
PIC18F23K20/24K20/25K20/26K20/43K20/44K20/45K20/46K20 Data Sheet
28/40/44-Pin Flash Microcontrollers with nanoWatt XLP Technology
(DS41303)
Consult this document for information regarding the PIC18F4XK20 28/40/44-pin
Flash-based, 8-bit CMOS microcontrollers with XLP technology.
PICkit™ 3 In-Circuit Debugger/Programmer User’s Guide for MPLAB® X
IDE (DS52116)
Consult this document for instructions on how to use the PICkit™ 3 microcontroller
programmer software and hardware.
MPLAB® Code Configurator User’s Guide (DS40001725)
Consult this document for information on how to use the MPLAB® Code Configurator
(MCC). Access www.microchip.com/code_configurator.html for more information on
the MCC.
MPLAB® ICD 3 In-Circuit Debugger User’s Guide for MPLAB X IDE
(DS50002081)
Consult this document for more information pertaining to the features and functions of
the MPLAB® ICD 3 software.
MPLAB® X IDE User’s Guide (DS50002027)
Consult this document for more information pertaining to the installation and features
of the MPLAB X Integrated Development Environment (IDE) software.
Readme Files
For the latest information on using other tools, read the tool-specific Readme files in
the Readmes subdirectory of the MPLAB IDE installation directory. The Readme files
contain update information and known issues that may not be included in this user’s
guide.
2006-2015 Microchip Technology Inc.
DS40001296C-page 7
44-Pin Demo Board User’s Guide
THE MICROCHIP WEB SITE
Microchip provides online support via our web site at www.microchip.com. This web
site is used as a means to make files and information easily available to customers.
Accessible by using your favorite Internet browser, the web site contains the following
information:
• Product Support – Data sheets and errata, application notes and sample
programs, design resources, user’s guides and hardware support documents,
latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQs), technical
support requests, online discussion groups, Microchip consultant program
member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip
press releases, listing of seminars and events, listings of Microchip sales offices,
distributors and factory representatives
DEVELOPMENT SYSTEMS CUSTOMER CHANGE NOTIFICATION SERVICE
Microchip’s customer notification service helps keep customers current on Microchip
products. Subscribers will receive e-mail notification whenever there are changes,
updates, revisions or errata related to a specified product family or development tool of
interest.
To register, access the Microchip web site at www.microchip.com, click on Customer
Change Notification and follow the registration instructions.
The Development Systems product group categories are:
• Compilers – The latest information on Microchip C compilers, assemblers, linkers
and other language tools. These include all MPLAB X IDE and MPLAB XC8
compilers; all MPLAB assemblers (including MPASM™ assembler); all MPLAB
linkers (including MPLINK™ object linker); and all MPLAB librarians (including
MPLIB™ object librarian).
• Emulators – The latest information on Microchip in-circuit emulators.This
includes the MPLAB REAL ICE™ and MPLAB ICE 2000 and MPLAB ICE 4000
in-circuit emulators.
• In-Circuit Debuggers – The latest information on the Microchip in-circuit
debuggers. This includes MPLAB ICD 3 in-circuit debuggers and PICkit™ 3
debug express.
• MPLAB® X IDE – The latest information on Microchip MPLAB X IDE, the
Windows® Integrated Development Environment for development systems tools.
This list is focused on the MPLAB IDE, MPLAB IDE Project Manager, MPLAB
Editor and MPLAB SIM simulator, MPLAB IDE Project Manager as well as general
editing and debugging features.
• Programmers – The latest information on Microchip programmers. These include
production programmers such as MPLAB REAL ICE in-circuit emulator, MPLAB
ICD 3 in-circuit debugger and MPLAB PM3 and PRO MATE® device
programmers. Also included are nonproduction development programmers such
as PICSTART® Plus and PICkit 2 and 3.
DS40001296C-page 8
2006-2015 Microchip Technology Inc.
Preface
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
•
•
•
•
Distributor or Representative
Local Sales Office
Field Application Engineer (FAE)
Technical Support
Customers should contact their distributor, representative or field application engineer
(FAE) for support. Local sales offices are also available to help customers. A listing of
sales offices and locations is included in the back of this document.
Technical support is available through the web site at:
http://www.microchip.com/support.
REVISION HISTORY
Revision A (August 2006)
• Initial release of this document.
Revision B (December 2006)
•
•
•
•
•
•
Updated Chapter 1, “PICkit™ 2 Overview”
Added Chapter 2, “Mid-Range PIC® Microcontroller Architectural Overview”
Added Chapter 3, “Mid-Range PIC® Microcontroller Architectural Overview”
Changed PICmicro® to PIC®
Changed PICkit® to PICkit™
Removed Development Systems Information Line from Customer Support
bulleted list
• Updated schematic in Appendix
Revision C (May 2015)
•
•
•
•
•
Updated the Recommended Reading section in Preface
Updated for new PIC18F45K20 device
Removed assembly code and added reference to C code
Removed lessons 6, 8, 9, 10, 11, 12 in chapter 3
Replaced MPLAB IDE, PICkit 2 and ICD 2 references with MPLAB X IDE, PICkit 3
and ICD 3, respectively.
2006-2015 Microchip Technology Inc.
DS40001296C-page 9
44-Pin Demo Board User’s Guide
NOTES:
DS40001296C-page 10
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Chapter 1. 44-Pin Demo Board Overview
1.1
INTRODUCTION
The 44-Pin Demo Board is a small and simple demonstration PCB for Microchip’s
44-pin Thin Quad Flatpack (TQFP) PIC® microcontroller units (MCU). It is populated
with a PIC18F45K20 MCU, eight LEDs, push button and potentiometer. The demo
board has several test points to access the I/O pins of the MCU and a surface mount
prototyping area. The MCU can be programmed with the PICkit™ 3 microcontroller
programmer or the MPLAB® ICD 3 using the RJ-11 to 6-pin inline adapter (AC164110).
1.2
HIGHLIGHTS
This chapter outlines:
• Devices supported by the 44-Pin Demo Board
• 44-Pin Demo Board Overview
• Running the Default Demonstration
1.3
DEVICES SUPPORTED BY THE 44-PIN DEMO BOARD
The 44-Pin Demo Board can be used with virtually any 44-pin Thin Quad Flatpack
(TQFP) PIC MCU. The assembled 44-Pin Demo Board is populated with a
PIC18F45K20 microcontroller.
Additional 44-Pin Demo Boards can be ordered from Microchip Technology or
distributors via part number, DM164120-2. The part comes with one assembled and
two blank 44-Pin Demo Boards. The blank demo board can be used for evaluating or
prototyping circuits using any of the 44-pin devices listed below.
44-Pin TQFP Flash Devices:
•
•
•
•
•
•
•
•
•
•
•
•
•
PIC16F74
PIC16F777
PIC16F877A
PIC16F917
PIC18F4320
PIC18F4410
PIC18F4431
PIC18F4480
PIC18F4515
PIC18F4525
PIC18F4585
PIC18F4620
PIC18F4685
2006-2015 Microchip Technology Inc.
•
•
•
•
•
•
•
•
•
•
•
•
PIC16F747
PIC16F871
PIC16F887
PIC18F4220
PIC18F4321
PIC18F4420
PIC18F4450
PIC18F44J10
PIC18F4520
PIC18F4550
PIC18F45J10
PIC18F4680
•
•
•
•
•
•
•
•
•
•
•
•
PIC16F77
PIC16F874A
PIC16F914
PIC18F4221
PIC18F4331
PIC18F4423
PIC18F4455
PIC18F4510
PIC18F4523
PIC18F4580
PIC18F4610
PIC18F4682
DS40001296C-page 11
44-Pin Demo Board User’s Guide
1.4
44-PIN DEMO BOARD OVERVIEW
The 44-Pin Demo Board is populated with a PIC18F45K20 MCU (U1), eight LEDs
(DS1-DS8), push button (SW1) and potentiometer (RP1). The board layout is shown in
Figure 1-1. The demo board has several test points to access the I/O pins of the MCU
and a surface mount prototyping area. The MCU can be programmed with the
PICkit™ 3 microcontroller programmer from header P1.
FIGURE 1-1:
44-PIN DEMO BOARD
PICkit™ 3 Programming Header
Push Button SW1
Potentiometer RP1
LEDs DS1-DS8
3
Surface Mount
Prototyping
Area
DS40001296C-page 12
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Overview
1.5
RUNNING THE DEFAULT DEMONSTRATION
The assembled 44-Pin Demo Board comes preprogrammed with a MCC developed
demonstration program. To use this program, power the demo board (3.0-5.5 VDC)
using a PICkit™ 3 microcontroller programmer, or a bench power supply connected to
header P2.
To use the PICkit™ 3 microcontroller programmer follow these steps:
1.
2.
3.
4.
5.
6.
7.
Connect it to a PC USB port using the USB cable
Start the MPLAB X IDE application
Open the project containing the code for 44-Pin Demo Board
Right click on Project to open Project Properties
Go to Configuration>PICkit™ 3>Option Categories: Power
Select the check box “Power target circuit from PICkit 3”
Select the power supply voltage between 3.0 to 5V. The demo program will first
light the DS1 LED.
8. Press the push button switch (SW1), to cycle demo program through different
states along with the potentiometer (RP1). The demo program is explained in
more details in Chapter 3. “44-Pin Demo Board Lessons”.
2006-2015 Microchip Technology Inc.
DS40001296C-page 13
44-Pin Demo Board User’s Guide
NOTES:
DS40001296C-page 14
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Chapter 2. PIC® Microcontroller Architectural Overview
2.1
INTRODUCTION
This chapter provides a simple overview of the mid-range PIC® microcontroller
architecture.
SIMPLIFIED MID-RANGE PIC® MICROCONTROLLER BLOCK
DIAGRAM
FIGURE 2-1:
INT
13
Flash
4k x 14
Program
Memory
8
Data Bus
Program Counter
RAM
256 bytes
File
Registers
8-Level Stack (13-bit)
Program 14
Bus
9
RAM Addr
Addr MUX
Instruction Reg
Direct Addr
7
8
Indirect
Addr
FSR Reg
STATUS Reg
8
3
Instruction
Decode and
Control
OSC1/CLKI
OSC2/CLKO
MUX
ALU
8
Timing
Generation
W Reg
Internal
Oscillator
Block
2006-2015 Microchip Technology Inc.
DS40001296C-page 15
44-Pin Demo Board User’s Guide
2.2
MEMORY ORGANIZATION
PIC microcontrollers are designed with separate program and data memory areas. This
is called Harvard architecture and it allows faster execution as the address and data
buses are separate and do not have to do double duty.
Data Memory is divided into File registers, Special Function registers (SFRs) and
General Purpose Registers (GPRs). File registers are used by the CPU during
execution for quick access; for example, they are used in the case of a loop variable.
Instructions referring to File registers use seven bits; therefore, only 128 File registers
can be addressed. These registers are arranged in groups of registers called register
banks. Access to a register bank is controlled through the STATUS register. Additional
banks may or may not be implemented, depending on the device.
The application program interacts with the peripherals and core features through
Special Function Registers. SFRs contain peripheral Control registers for operation
mode selection, peripheral Data registers for data communication, interrupts etc. The
application program writes into these registers so that these peripherals called device
drivers can be used.
The General Purpose Registers are also called RAM. They are accessible to program
and are used for storing both global and static application variables and also the stack
containing local variables and other data.
Program Memory is accessed via the program counter (PC), which stores the program
to be executed. The execution unit of the PIC device uses the PC value to get the
location of the next queued program instruction to be executed and it auto-increments
the PC. The bit length of the PC changes with the device and the program memory size.
Refer to the device specific data sheet for PC details and implementation.
The device clock can be provided either from an internal on-chip oscillator or an
external crystal oscillator. The application can select the clock using the configuration
fuse settings.
2.3
PROGRAMMING
PIC devices are RISC-based MCUs optimized for C programming. This makes C code
written for PIC devices and compiled to small-size assembly code take up less program
memory and be more efficient in terms of program performance (i.e., higher MIPS).
The compiler optimizes the code to take less stack, data and program memory and it
initializes them. Hence, the programmer can focus on peripheral drivers and the
application code. For further information on the C compiler for 8-bit PIC devices, refer
to the MPLAB® XC8 C Compiler User’s Guide (DS50002053).
DS40001296C-page 16
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Chapter 3. 44-Pin Demo Board Lessons
3.1
INTRODUCTION
The following lessons cover basic 44-Pin Demo Board features. Refer to applicable
documents as needed. Any updates to the applicable documents are available on
Microchip’s web site.
The code and hex files may be installed from Microchip’s web site.
3.2
PROGRAM FLOWCHART
Figure 3-1 shows the initialization of the program. The 44-Pin Demo Board program
contains seven lessons or states of program. These states are mentioned in the
flowchart as actions or tasks to be performed. These seven lessons show the basic
peripherals and their working in PIC MCUs. The initialization program is generated
using the MPLAB Code Configurator (MCC) as explained in the following sections. It
initializes external INT0 for switch SW1, Analog-to-Digital Converter (ADC) input for
potentiometer RP1, Port D output for LED, and Timers, etc.
As shown in Figure 3-1, a key press changes the current action to the next action. The
actions are implemented in circular fashion (i.e., after the last action restarts to execute
from the first one).
FIGURE 3-1:
INITIALIZATION FLOWCHART
Start
Initialize
NO
Switch Interrupt?
B
YES
Advance Action to Next
A
2006-2015 Microchip Technology Inc.
DS40001296C-page 17
44-Pin Demo Board User’s Guide
3.3
44-PIN DEMO BOARD LESSONS
The list of lessons is as follows:
•
•
•
•
•
•
•
Lesson 1: Hello World (Light a LED)
Lesson 2: Blink (Delay Loop)
Lesson 3: Rotate (Move the LED)
Lesson 4: Analog-to-Digital
Lesson 5: Variable Speed Rotate
Lesson 6: Reversible Variable Speed Rotate
Lesson 7: Interrupt Priorities
3.3.1
Lesson 1: Hello World (Light a LED)
The first lesson shows how to turn on a LED and discusses the I/O pin structures. This
is the PIC microcontroller version of “Hello World”.
The LEDs are connected to PORTD from RD0 to RD7 in common cathode
configuration. When one of these I/O pins drives high, the LED turns on. The I/O pins
can be configured for input or output. On start-up, the default is input. The TRIS Special
Function Register bits use the convention of ‘0’ for output and ‘1’ for input. Digital output
is targeted, so these must be configured. The LAT register acts as buffer to the output
value on the port pin in output configuration.
After setting TRISD as output port in the program, assigning logic ‘1’ to the LATD0 bit
of the LATD register turns LED on and vice versa.
FIGURE 3-2:
HELLO WORLD FOR PIC® MCU
A
B
NO
Action==LED_ON?
YES
Set Port Pin to Light
LED
Wait for State Change
DS40001296C-page 18
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Lessons
3.3.2
Lesson 2: Blink (Delay Loop)
The first lesson showed how to turn on a LED; this lesson shows how to make it blink
(see Figure 3-3). While this might seem a trivial change from Lesson 1, it gives a
context to explore several more peripherals.
FIGURE 3-3:
LED BLINK AT PERIODIC RATE USING TIMER0
A
B
NO
Action==LED_BLINK?
YES
Set Timer Delay
NO
Timer Overflow?
YES
Change LED Port Pin
Status
The LED will blink (i.e., toggled from its current state periodically). The period of
toggling is adjusted using a delay loop either in software or hardware. Timer0 is a
commonly found core-independent Timer peripheral in almost all 8-bit PIC devices. In
the baseline and mid-range devices, Timer0 is an 8-bit timer/counter while in high-end
8-bit PIC MCUs, Timer0 can also be configured as a 16-bit timer/counter. Timer0 can
be clocked from either PIC device instruction clock or from an external pin. Once
selected, the timer clock can be further prescaled to a smaller clock. Timer0 has eight
prescaler options from 1:1 to 1:256 prescaling of the clock.
The TMR0 register holds the timer counter value. It can be preloaded to vary the delay.
In Figure 3-3, Timer0 is preloaded with a count. As an up-counter, Timer0 counts to the
maximum value (i.e., 255 for eight bits or 65535 for 16 bits). After counter reaches its
maximum value, it rolls over to ‘0’ and Timer0 overflow interrupt occurs. The MCU is
then interrupted and jumps to a predetermined location to execute the interrupt routine
and perform a delay loop task, where LED status is toggled. This is called hardware
delay.
The advantage of hardware delay is that delay can be performed independently of the
PIC MCU core and the MCU core is free to do other tasks instead of being blocked by
the delay task, thus saving CPU cycles and increasing application performance.
To use Timer0, follow these steps in the Configuration register, T0CON:
1. Set the number of bits for the counter (i.e., eight or 16 and select the internal
clock).
2. Select the clock edge for Timer operation and prescaler.
3. Write the interrupt routine for Timer0 interrupt void interrupt ISR() and
write custom code in it as per application.
4. Start Timer0.
2006-2015 Microchip Technology Inc.
DS40001296C-page 19
44-Pin Demo Board User’s Guide
The software delay includes running a loop, either for or while loop in C. Every
instruction in the PIC device takes four clock cycles (i.e., one instruction cycle is equal
to four clock cycles). In loop, the initialization is done only once; after that, a condition
is checked and an increment or decrement operation is performed on the variable that
takes part in the condition check. This requires one instruction cycle to perform the
math operation, and another instruction cycle for the condition check. Therefore, if the
clock is running at 4 MHz, a single execution of the loop for the 8-bit integer takes 2 us
of delay time. The advantage of software delay is that it does not require help from
peripherals in order to perform. The disadvantages are that CPU cycles are wasted in
delay, blocking other important tasks, and the user has to do all calculations at C
instruction level, which may vary depending on the compiler optimization for the delay
program (i.e., if the compiler uses the RAM location for the variable, another instruction
is required to load or store the variable in RAM).
3.3.3
Lesson 3: Rotate (Move the LED)
Building on lessons 1 and 2, which showed how to light up a LED and then make it blink
with a delay loop, this lesson adds rotation. It will light up DS8 and then shift it to DS7,
then to DS6, to DS8, and then back to DS1.
FIGURE 3-4:
ROTATE LED AT FIXED RATE
A
B
NO
Action==LED_
ROTATE?
YES
Set Variable with
Value 1
Set Timer Delay
NO
Timer Overflow?
YES
Rotate the Variable
Value by ‘1’
Assign Variable to
LED Port
DS40001296C-page 20
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Lessons
The program flow to rotate the lighting of the LEDs is listed below:
1.
2.
3.
4.
First, initialize the I/O port and the display.
Copy the display variable to the I/O port.
Delay for a little while.
Rotate the display.
In this lesson, the delay is given by hardware Timer0 previously explained. An
unsigned 8-bit integer variable is used to store value of decimal ‘1’. To rotate the
lighting of the LEDs, after Timer0 delay, this variable is shifted left so that only one bit
in decimal value is logic ‘1’ while the other are logic ‘0’. The rate at which the lighting
of the LEDs rotates depends on Timer0 delay. Next the variable is updated with the
new value; then, it is assigned to the I/O port connected to the LEDs (i.e., LATD register
for PORTD).
3.3.4
Lesson 4: Analog-to-Digital
This lesson shows how to configure the ADC, run a conversion, read the analog voltage
controlled by the potentiometer (RP1) on the board, and display the high-order eight
bits on the LEDs.
FIGURE 3-5:
ADC DISPLAY ON LED
A
B
NO
Action==A/D?
YES
Configure ADC for
Port Input
Set Timer Delay
NO
Timer Overflow?
YES
Start ADC Acquisition
NO
ADC Done?
YES
Set the High-Order
Bits of ADC Out to
LED Port
2006-2015 Microchip Technology Inc.
DS40001296C-page 21
44-Pin Demo Board User’s Guide
PIC18F45K20 has an on-board ADC with ten bits of resolution on any of the 13
channels. The converter can be referenced to the device’s VDD or an external voltage
reference. The 44-Pin Demo Board references it to VDD as provided by the PICkit 3
microcontroller programmer. The answer from the ADC is represented by a ratio of the
voltage to the reference (see Equation 3-1).
EQUATION 3-1:
ADC = V VREF 1023
Converting the answer from the ADC back to voltage requires solving for V (see
Equation 3-2).
EQUATION 3-2:
V = ADC 1023 V REF
Two of the three factors on the right-hand side of the equation are constants and may
be calculated in advance. This eliminates the need to actually divide, but it still requires
fixed or floating point multiply to solve the equation on the fly.
However, calculating the voltage is sometimes only the first step. There may be
additional math to calculate the meaningful data from the sensor. For example, when
reading a thermistor, calculating the voltage is only the first step on the way to getting
the temperature.
There are other means to convert ADC values, including a straight table look-up or a
piece-wise linear interpolation. Each of these represents different speed/memory
trade-offs.
The schematic in Appendix A. “Hardware Schematics” shows that the wiper on the
potentiometer is connected to pin RA0 on PIC18F45K20.
Below is the checklist for this lesson:
1.
2.
3.
4.
Configure PORTA as an analog input, TRISA<0> = 1, ANSEL<0> = 1.
Select channel in ADCON0.
Select VREF source in ADCON1.
Select justification, acquisition time and clock in ADCON2.
Refer to the device-specific data sheet for further information on control registers. The
high-order eight bits of the ADC result are then displayed on the LED port neglecting
the lower two bits.
DS40001296C-page 22
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Lessons
3.3.5
Lesson 5: Variable Speed Rotate
Lesson 5 combines lessons 3 and 4 by using the ADC to control the speed of rotation.
FIGURE 3-6:
ROTATE LED CLOCKWISE OR FORWARD AT VARIABLE
RATE
A
Action==VAR_LED
_ROTATE?
NO
YES
Set Variable with Value
‘1’
Configure ADC for Port
Input
Set Timer1 Delay for
ADC
Set Timer2 Delay for
LED Rotation
NO
NO
Timer1 Overflow?
Timer2 Overflow?
YES
YES
Start ADC Acquisition
Rotate Variable by ‘1’
NO
ADC Done?
Assign Variable to LED
Port
YES
Change Timer2 Delay
Proportional to ADC
Out
In this lesson, Timer0 is used as variable delay counter, the delay of which is changed
according to the ADC output of the RP1 potentiometer connected to the ADC channel,
AN0. Timer1 is used to set the sampling frequency for the ADC. When Timer1 times
out, it enables the ADC conversion. The ADC output is used to change the Timer0
delay. As the potentiometer RP1 resistance changes, the rate at which the LED is
rotating changes accordingly.
2006-2015 Microchip Technology Inc.
DS40001296C-page 23
44-Pin Demo Board User’s Guide
3.3.6
Lesson 6: Reversible Variable Speed Rotate
Lesson 6 is similar to Lesson 5 (i.e., the system and peripherals have the same
functions as explained in Lesson 5, except that the LED rotation direction is reversed).
FIGURE 3-7:
ROTATE LED ANTI-CLOCKWISE/REVERSE AT VARIABLE
RATE
A
B
Action==REVERSE_
VAR_LED_ROTATE?
NO
YES
Set Variable with Value 0x80
Configure ADC for Port Input
Set Timer1 Delay for ADC
Set Timer2 Delay for LED
Rotation
NO
NO
Timer1 Overflow?
Timer2 Overflow?
YES
YES
Start ADC Acquisition
Rotate Variable by ‘1’ in
Reverse Direction
ADC Done?
Assign Variable to LED
Port
NO
YES
Change Timer2 Delay
Proportional to ADC Out
DS40001296C-page 24
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Lessons
3.3.7
Lesson 7: Interrupt Priorities
This lesson focuses on interrupt priorities in high-end PIC16F and PIC18F devices. The
external interrupt INT0 is connected to the SW1 switch which is a high-priority interrupt.
The Timer0 overflow interrupt is a low-priority interrupt, which is used to blink LED DS0
at a constant rate set by the user. When SW1 is pressed, the high-priority external
interrupt takes priority over the low-priority Timer0 interrupt and stops LED from
blinking for a second and lights the DS1 LED. After a second, the DS1 LED is turned
off and Timer0 resumes blinking the DS0 LED. This lesson explains when the
low-priority interrupt is being serviced; it can be interrupted by high-priority interrupts.
FIGURE 3-8:
INTERRUPT PRIORITY TEST
A
B
NO
Action==INTERRUPT_TEST?
YES
Init Timer0 for LED1 Blink
Set Timer1 Low and External Switch
High Interrupt Priority
NO
NO
Timer1 Overflow?
Switch Press?
YES
YES
Change LED1 Status
Stop LED 1 Blink, ON LED2 for
1 Second
Note: The switch interrupt is high priority; therefore, it will automatically
stop Timer interrupt, which is low priority; however, it will resume when
switch interrupt is done delaying.
2006-2015 Microchip Technology Inc.
DS40001296C-page 25
44-Pin Demo Board User’s Guide
3.4
LESSONS NOT INCLUDED
There are some tasks which are inherently part of the program such as switch
debouncing or Timer0 delay. Hence, these lessons from the previous versions of this
user guide are not included as separate lessons in the current version. Following is the
list of lessons that can be found in previous versions of the document:
•
•
•
•
3.5
Function Calls
Timer0
Indirect Data Addressing
Look-up Table
MPLAB® CODE CONFIGURATOR (MCC)
The MPLAB® X Code Configuration tool is used in this project to generate driver
application programming interfaces (APIs) for the peripherals used. It is the simplest
and fastest way to generate code. The peripherals used in this program are:
•
•
•
•
•
Timer0 – delay timer
Timer1 – used for setting ADC sampling frequency
ADC – channel AN0 for potentiometer RP1
INT0 – external interrupt for switch SW1
PORTD – LED output port
To install the MCC, go to Tools>Plugins>Available Plugins>MPLAB X Code
Configurator>Install.
To start and use the MCC after installation, go to Tools>Embedded>MPLAB Code
Configurator.
FIGURE 3-9:
ADC SETTINGS USING THE MCC
As seen in Figure 3-9, the clock, VREF, acquisition time, channel selection, interrupt
enable are all set by GUI at one place.
DS40001296C-page 26
2006-2015 Microchip Technology Inc.
44-Pin Demo Board Lessons
FIGURE 3-10:
TIMER0 SETTINGS USING MCC
Similar to Figure 3-9, Figure 3-10 shows the Timer0 settings. In both figures, the port
pin settings are given on the right-hand side. In a similar way, other settings are
performed in the MCC. After all system settings are done, click the Generate Code
button in the upper left-hand side corner of the MPLAB Code Configurator window. This
will generate all peripheral-related code in a MCC file structure along with the main.c
file, where the user can call these initialization functions at will and focus on the actual
application code.
2006-2015 Microchip Technology Inc.
DS40001296C-page 27
44-Pin Demo Board User’s Guide
NOTES:
DS40001296C-page 28
2006-2015 Microchip Technology Inc.
44-PIN DEMO BOARD
USER’S GUIDE
Appendix A. Hardware Schematics
A.1
INTRODUCTION
This appendix contains the 44-Pin Demo Board schematic, PCB layout and Bill of
Materials (BOM).
44-PIN DEMO BOARD SCHEMATIC DIAGRAM
PIC®
FIGURE A-1:
2006-2015 Microchip Technology Inc.
DS40001296C-page 29
44-Pin Demo Board User’s Guide
DS40001296C-page 30
FIGURE A-2:
44-PIN DEMO BOARD SILKSCREEN
FIGURE A-3:
44-PIN DEMO BOARD TOP COPPER
2006-2015 Microchip Technology Inc.
Hardware Schematics
FIGURE A-4:
TABLE A-1:
44-PIN DEMO BOARD BOTTOM COPPER
44-PIN DEMO BOARD BILL OF MATERIALS
Bill of Materials
Qty
Description
C1, C2, C3
R5-R12
R1, R3
R2
RP1
DS1-DS8
SW1
U1 – Microcontroller
P1
Designation
3
8
2
1
1
8
1
1
1
JP1
1
Rubber feet
4
Capacitor, Ceramic, 0805 SMT, 0.1 F, 16V, 5%, X7R
Resistor, 0805 SMT, 750, 5%, 1/8W
Resistor, 0805 SMT, 1 k 5%, 1/8W
Resistor, 0805 SMT, 10 k, 5%, 1/8W
Potentiometer 10 k, thumbwheel
LED, 0805 SMT, Red Clear
Switch, push button, momentary
44-pin PIC® MCU
Connector, header, right-angle, 6-pin, 0.100” spacing,
0.025” square
Connector, header, 2-pin, 0.100” spacing, 0.025”
square
Bumpon square, 0.40 x 0.10, black
2006-2015 Microchip Technology Inc.
DS40001296C-page 31
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