Using PIC ® Microcontrollers
by David Benson
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"MICROCONTROL'N APPS" is an intermediate level applications guide covering Microchip Technology's PIC ® Microcontrollers. Serial communication as a means of transferring data between PIC microcontrollers and peripheral chips and also between two or more PIC microcontrollers is described. Use of the 93C46 serial EEPROM is detailed as an example. Since we live in an analog world, A/D and D/A are discussed with several methods illustrated for each. Conditioning signals from sensors with an analog voltage output is described. Interfacing PIC microcontroller-controlled systems with humans requires some math, binary to decimal conversion and vice versa, alphanumeric LCD interfacing and scanning keypads. Single wire serial communication with a PIC-controlled LCD module which can be built by the reader is included. A digital thermometer project brings these topics together as an example. The book also explains how to establish serial communication between a PIC microcontroller and a PC via a RS-232 conversion circuit and a terminal program. These techniques are used in a digital voltmeter/data logger experiment for uploading data to a PC for display plus graphing using a spreadsheet program. Moving up or down from the now familiar PIC16F84 to other devices is covered in detail so that you will easily be able to work with the new devices being introduced by Microchip. Finally, use of the Microchip in-circuit debugger (ICD2) is described. "Microcontrol'n Apps" gives the reader the tools to design, build, and debug intermediate level microcontroller-based instrumentation and systems. By David Benson (8-1/2 x 11 format, 437 pages, $44.95).
TABLE OF CONTENTS
PREFACE
INTRODUCTION
PRODUCT OVERVIEW
CIRCUIT MODULES FOR EXPERIMENTS
USING OP-AMPS
SERIAL COMMUNICATION
SHIFT REGISTERS
Serial In, Parallel Out Shift Register - 74HC164
Parallel In, Serial Out Shift Register - 74HC165
Serial In, Parallel Out Shift Register - 74HC595
SERIAL EEPROMS
Demo Circuit
Main Program - Initial Test
SERIAL COMMUNICATION BETWEEN TWO PIC MICROCONTROLLERS
LIQUID CRYSTAL DISPLAY INTERFACE
1 X 16 LCD
Pins And Functions
Data vs. Instruction
Display Control
Character Addresses
LCD Operation
PIC/LCD Circuit
Timing And Pulsing
Testing The Circuit
Display RAM
Initialization
ASCII
Example Routines For LCD
Fill Display With Blanks
Display "HELLO"
LCD Initialization
Character Addresses
More on Alphanumeric Character Addresses
Display 16 Characters
Display Hex Byte Subroutine
Blanks
Separate A Hex Byte Into Two ASCII Digits
Hex Digit To ASCII Conversion
Hex To Bits Subroutine
Program Listing
To Use/Test Display Hex Byte
4-Bit Mode
LCD Module Serial Interface
LCD Experiments
More About ASCII
LCD Font table
SCANNING KEYPADS
Software Design
Scan Decimal Subroutine
Using Keypad And LCD With PIC Microcontroller
Debounce
Function Keys
DIGITAL TO ANALOG CONVERSION
Do It Yourself D/A Using A Resistor Network
8-Bit Parallel D/A Converter - AD558
Do It Yourself D/A Using Pulse Width Modulation
PWM Basics
Low Pass Filters
PWM Using A Filter With Unity Gain Follower
More PWM Philosophy
Analog Output - Increase/Decrease Buttons
PWM Using Software, TMR0 And Interrupts -
Philosophy
Hardware PWM
8-Bit Serial D/A Converter - MAX522
Output A Voltage Level
Output A Ramp Voltage
Output A Sine Wave
SENSORS - ANALOG VOLTAGE OUTPUT
LM335 Temperature Sensor
Offset And Scale
Three Amplifier Design
Single Amplifier Design
Why 1 Op-amp vs. 3 Op-amps?
ANALOG TO DIGITAL CONVERSION
PIC Pin And RC Time Constant
Measuring Resistance
PIC16F870 On-Board 10-bit A/D
A/D Control Registers
A/D Conversion Procedure
Example
PIC16F870 On-Board 10-bit A/D - Using Only the Most Significant 8 bits
Example
PIC12F675 On-Board 10-bit A/D
A/D Control Registers
A/D Conversion Procedure
Example
10-bit A/D Differences
USING COMPARATORS
Comparator Control Register - CMCON
Voltage Reference Control Register - VRCON
Single Comparator Example
Comparator Interrupts
MATH ROUTINES
Instructions
Arithmetic
Addition
Subtraction
Multiplication
Double Precision
Addition
Subtraction
Multiplication
Multiply A 2-Byte Binary Number By Decimal 10
8-Bit X 8-Bit Multiply, 2-Byte Result
DECIMAL INTERFACE
3-digit decimal to 8-bit binary
Using the 3-digit decimal to 8-bit binary decimal
entry program
8-bit to 3-digit BCD
Display result of 8-bit binary to 3-digit BCD
16-bit binary to 5-digit BCD -
range 0x0000 to 0x7FFF
16-bit binary to 5-digit BCD -
range 0x0000 to 0xFFFF
DIGITAL THERMOMETER
Building blocks
Rounding off
Displaying temperature via a LCD
SIMPLE DIGITAL VOLTMETER EXPERIMENT
TALKING TO A PIC MICROCONTROLLER WITH A PC
VIA A WINDOWS TERMINAL PROGRAM
"U-turn" experiment
PC-to-PC "2-lane highway" experiment
Importing a text file into a spreadsheet program
Windows XP - Microsoft Works 7.0
PC/PIC Microcontroller
PC baud rates
Modify ser_out subroutine
Modify ser_in subroutine
PIC to PIC at 4800 baud, LSB first
RS-232 interface for a PIC microcontroller
RS-232 converter circuit using MAX233
PC to PIC microcontroller serial communication
Display one ASCII character via 8 LEDs
PIC microcontroller to PC serial communication
Send one ASCII character
Code for formatting PIC microcontroller
data on a PC screen
PC to PIC/LCD
Control characters
Sending a text file (control characters
and data)
SIMPLE DATA LOGGER EXPERIMENT
Main program
Data logging
Display data sequentially via LCD
Uploading data to a PC
Code
Operating procedure
Spreadsheet and graphing data - Windows XP
MOV'n UP OR DOWN
Pin function options and how to select them
Clock oscillator options
Example - PIC12F627/628
Example - PIC12F629/675
External reset vs. digital I/O option
Example - PIC12F627/628
Example - PIC12F629/675
Special function registers
General purpose file registers
CBLOCK assembler directive
Configuration words
PIC16F628
Pins and functions
Package
Ports
Architecture - overview
Program memory
File registers
Special purpose registers - overview
Status register
Option register
Program counter
Control registers
Comparator control register - CMCON
Configuration bits
PIC16F628 programming examples
Example - pict1.asm adapted
Example - internal 4 MHz clock, no MCLR
PIC12F675 - 8-PIN MICROCONTROLLER
Pins and functions
Packag
Ports - GPIO
Clock oscillator options - covered previously
External reset vs. digital input pin (GP3) -
covered previously
Architecture - overview
Program memory
File registers
Special purpose registers - overview
Status register
Option register
Program counter
Control registers
Comparator control (CMCON) register
Analog select (ANSEL) register
Tristate I/O (TRISIO) register
Configuration bits
Calibrating the internal 4 MHz RC clock oscillator
Device programming considerations related to
internal oscillator calibration
Example program
Led pattern
Internal reset
Internal clock oscillator
PIC16F870
Pins and functions
Package
Ports
Architecture - overview
Program memory
File registers
Special purpose registers - overview
Status register
Option register
Program counter
Control registers
A/D control (ADCON1) register
Configuration Bits
F870 vs. F84
CIRCUIT MODULES FOR F870 EXPERIMENTS
Building Your Own Simple Test Board - 87s Board
87s Companion Board
PROGRAMMING THE F870 USING A DEVICE PROGRAMMER
First F870 Program - To be programmed via a
Device Programmer
PORTING YOUR APPLICATION FROM F84 To F870 - F870
PROGRAMMED VIA A DEVICE PROGRAMMER
PIC16F877
Disable A/D on port E
Connect both power and both ground pins
DEBUG'n
GETTING STARTED
PIC16F87x series
F870 - my candidate for the debug'n experimenter's
part of choice
F876 - my second choice
F84 vs. F870 for learning purposes
Device programmer vs. bootloader vs. ICD2
Bootloaders
Microchip ICD2
What a debugger can do for you
Debugging methodology
Single stepping
Breakpoint
Watch window
Debugging
MICROCHIP ICD2
Description
User Board = Target Board
Using The Microchip ICD2
General considerations
First project
First F870 program for use with ICD2
MPLAB Operations
Setting up the ICD2
Toolbar
To run a program in real time via the toolbar
To reset the F870 via the tool bar
Watch window
Single stepping
Break point
Break on address match
Clear breakpoint
Break on user halt
Powering down
Operating the 87s board stand alone after debug'n
Reconnecting the ICD2 After 87s board stand alone
operation
Firing up MPLAB and opening an existing project
Conclusion
Porting your application from F84 to F870 - F870 PROGRAMMED
VIA ICD2
USING THE ICD2 AS A MINI IN-CIRCUIT DEBUGGER FOR F84, F628 ETC.
APPENDICES
Appendix A - Sources
Appendix B - Hexadecimal Numbers
Appendix C - Program Listings vs. Page Numbers
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