AN861

AN861
Smart Air Handler using ProMPT™ and the PIC18F2539
Author:
Jon Burroughs
Microchip Technology Inc.
INTRODUCTION
In many heating, ventilation, and air conditioning
(HVAC) applications, air handler motors are either off,
or on at full speed. However, by adding variable speed
control to the air handler, significant energy savings
over the standard on/off control can be realized,
resulting in significantly reduced cost of operation.
This application note discusses the implementation of
a variable speed air handler that utilizes a single phase
AC induction motor. The task of designing the variable
speed air handler is greatly simplified by using the
Microchip Programmable Motor Control Processor
Technology (ProMPT) Single Phase Induction Motor
Control Evaluation Kit and the PIC18F2539
microcontroller.
The PIC18F2539 microcontroller is an Enhanced
FLASH microcontroller that features the Single Phase
Induction Motor Control (SPIMC) kernel. The SPIMC
kernel enables open loop variable frequency (VF) control and features a programmable voltage versus frequency curve. The PIC18F2539 microcontroller is a
natural choice for adding variable speed control to an
air handler application.
The ProMPT™ Single Phase Induction Motor Control
Evaluation Kit functions as an effective platform for
application development. It can be used to control
shaded pole and permanent magnet split capacitor
type motors. Adding specific features to support the air
handler application is accomplished by designing a
custom daughter board. In this application, the daughter board merely adds a user interface and temperature
sensor to the existing AC induction motor drive.
APPLICATION OVERVIEW
This application note shows how to add variable speed
control to an HVAC air handler. The application demonstrates heating only, and does not address control of
the heating element, which is assumed to be a simple
logic on/off control of a gas furnace or electrical heating
coils.
Usually, the target temperature is set by the thermostat
installed within a house. In this application, we use a
simple user interface consisting of two 8-segment
LEDs and two push buttons to set the target temperature. The actual air temperature is measured using the
Microchip TC1047 temperature sensor (see Figure 1).
The variable speed functionality is depicted in Figure 2.
The air handler operates at full speed when the air temperature is more than 5 degrees Celsius below the target temperature. When the air temperature is within 5
degrees of the target temperature, the air handler
speed is proportional to the difference in temperature.
As the air temperature within a house falls (for example, because it is cold outside), the air handler speed
increases, delivering more hot air into the house.
AC induction motors have a minimum operational
speed. To avoid on/off cycling when the actual temperature is near the target temperature, the lower end of
the variable speed response curve includes a hysteresis loop. In order for the air handler to turn on at the
minimum motor frequency, the actual temperature
must be more than 1°C below the target temperature.
However, to turn the air handler off, the difference
between the two temperatures must be zero. Because
on/off cycling is avoided, energy is conserved and air
handler operation is quieter and less obtrusive.
AC single phase induction motors are used in many
household applications, including HVAC, dishwashers,
clothes washers and dryers, garage door openers,
lawn mowers, and so on. ProMPT technology from
Microchip can greatly simplify design and reduce
time-to-market for all of these applications.
 2002 Microchip Technology Inc.
DS00861A-page 1
AN861
FIGURE 1:
APPLICATION BLOCK DIAGRAM
Blower
Thermocouple
Temp
Sensor
Variable Speed Drive
Thermostat
User Interface
FIGURE 2:
VARIABLE SPEED
RESPONSE
Max Freq
Motor
Frequency
Min Freq
Min ∆T
1°C
Max ∆T
5°C
Target Temp - Actual Temp
APPLICATION DESIGN WITH ProMPT
The application design is simplified enormously by
using the ProMPT Single Phase Induction Motor Control Evaluation Kit (see Figure 3). With the ProMPT
board, the task of designing an efficient AC induction
drive has already been accomplished. To create a variable speed air handler, it is necessary only to design a
simple daughter board that connects to the ProMPT
board’s I/O expansion connector and write the
necessary firmware (see Figure 4).
All information necessary to use the ProMPT board is
published in the following documents:
• ProMPT Single Phase Induction Motor Control
Evaluation Kit User’s Guide
• PIC18FXX39 Data Sheet
Readers may refer to these documents for more
detailed information on the ProMPT evaluation kit and
the PIC18F2539 microcontroller. These documents
may be obtained from the Microchip web site.
DS00861A-page 2
 2002 Microchip Technology Inc.
AN861
FIGURE 3:
ProMPT SINGLE PHASE INDUCTION MOTOR CONTROL EVALUATION KIT
FIGURE 4:
BLOCK DIAGRAM OF APPLICATION COMPONENTS
ProMPT Design
Accelerator
Application
Specific
Daughter Board
PIC18F2539
Temperature
Sensor
Voltage
Monitor
ADC
L
Power
Supply
PWM1
User Interface
 2002 Microchip Technology Inc.
M1
IGBT
Driver
PWM2
1-Phase
AC Input
G
Current
Monitor
Digital I/O
N
IGBT
H-Bridge
M2
Motor
G
DS00861A-page 3
AN861
APPLICATION SPECIFIC HARDWARE
Temperature Sensor
The features specific to the air handler application that
are designed onto an application specific daughter
board are described below:
Temperature measurement is made easy with a
Precision Temperature-to-Voltage Converter. This solid
state temperature sensor eliminates the need to
perform calibration that is required when using
thermocouples. Microchip’s TC1047A is a linear
voltage output temperature sensor, whose output is
directly proportional to the measured temperature.
Temperature is easily calculated without having to
construct calibrated lookup tables. The TC1047A can
accurately measure temperature from -40°C to 125°C,
a range more than adequate for a household HVAC
application. Supply voltage can vary from 2.5V to 5.5V
(see Figure 5). For more information, see the TC1047/
TC1047A data sheet. The temperature sensor requires
one analog input pin.
Display Module
A 2x8 segment display is used to display the temperature in Celsius. To save on I/O pins, control of the two
digits is multiplexed. Because of persistence of vision
in the human eye, the digits will appear to be illuminated simultaneously, even though they are actually
illuminated one at a time. Because the two decimal
segments are not required, a total of nine I/O pins are
used to control 14 LED segments.
Push Buttons
Two push buttons are used to adjust the temperature.
FIGURE 5:
PRECISION TEMPERATURETO-VOLTAGE CONVERTER
• Up - adjusts the target temperature upward.
• Down - adjusts the target temperature downward.
When either the Up or Down button is pressed, the
temperature begins blinking to indicate that a new target temperature is being set. The blinking target temperature increments or decrements with each press of
the up or down button. After five seconds elapse without a button press, the temperature display returns to
the present temperature and stops blinking. Each
button requires one I/O pin.
+5 VDC
+5 VDC
PIC18F2539
VDD
TC1047A
VSS
Note:
DS00861A-page 4
RA0
In this application, a low-pass filter and
shielded cable are used. See schematic
in Appendix A.
 2002 Microchip Technology Inc.
AN861
APPLICATION FIRMWARE
OVERVIEW
ProMPT motor control functionality is accessed by
using the pre-defined Application Program Interface
(API) described in Appendix B of this document (this
information is also available in Appendix E of the
ProMPT Design Accelerator Kit User’s Guide). By
using the defined API, powerful motor control tasks can
FIGURE 6:
be realized with no knowledge of the underlying
microcontroller activities. Figure 6 illustrates how the
user developed application firmware interacts with the
ProMPT motor control module through the Application
Program Interface (API). In essence, the API consists
of the library of ProMPT firmware functions that
enables control of the ProMPT module, without
needing to know the details of its operation.
MOTOR CONTROL ARCHITECTURE USING THE PIC18FXX39
ADCs, I/Os,
AUSART,
MSSP,
Timers
Smart Air Handler Application
Application Program Interface (API)
Parameter Values
PWMs
Hardware
ProMPT™ Motor Control Module
REQUIRED FILES
In order to take advantage of the pre-defined ProMPT
API, it is necessary to include several files when creating the project in MPLAB® IDE v6.10 These files are
described below.
Application Specific Files:
• SmartAir.c
• SmartAir.h
Main source code listing
Definition file for application
Required files when using the PIC18FXX39 device:
• motor.h
Definition file for the motor
• ProMPT_c18.h Prototypes of the API methods
used in the application
• 18F2539.lkr Linker file
 2002 Microchip Technology Inc.
DS00861A-page 5
AN861
APPLICATION FIRMWARE
FUNCTIONS
The firmware functions of the variable speed air
handler application are outlined below.
Note:
1.
2.
3.
Tasks denoted with an asterisk (*) are
related to control of the AC induction
motor.
Initialize the motor control module.*
Set the appropriate voltage frequency (VF)
curve for the motor.*
Execute a continuous loop that performs the
following tasks:
a) Read the temperature sensor connected to
ADC channel RA0.
b) Read the motor current, DC bus voltage,
and heatsink temperature.
c) Read and debounce the button inputs.
d) If a button is pressed, increment or decrement
the target temperature as necessary.
e) Check for faults.
f) Compare the actual temperature to the
target temperature.
g) Set the appropriate motor frequency.*
h) Update the LED display with actual or target
temperature.
i) Continuously control the AC induction
motor.*
EXAMPLE 1:
ProMPT_Init(0);
4.
If a fault is present, display fault on LED Fault
indicators:
E1 - Hardware transient current detection
E2 - Heat sink over temperature set at 70°C
E3 - Software over current detection set at 6A
E4 - DC bus over voltage set at 250V
E5 - DC bus under voltage set at 90V
By using the PIC18F2539 and the ProMPT based
Single Phase Induction Motor Control kernel, the biggest tasks (those involving motor control) become the
simplest ones. The ProMPT API methods make the
development of this application very easy. For example, to initialize the motor control module and set a new
VF curve for the motor, the API methods are as shown
in Example 1.
Constants like motorVFCurve and ACCELRATE are
defined in the motor.h file, and are dependant on the
specific motor used in the application.
The ProMPT API helps to make the application code
easy to write. See Appendix C for the location of the
complete source code with comments. A detailed flow
chart of the application firmware is shown in Figure 7.
MOTOR INITIALIZATION API METHODS
//Initialize the ProMPT block
//0 is the initial motor frequency
for (i=0;i<17;i++) {
//Set the V/F Curve for the motor
ProMPT_SetVFCurve(i,motorVFCurve[i]);
}
ProMPT_SetAccelRate(ACCELRATE); //Set other Motor Parameters
ProMPT_SetDecelRate(DECELRATE);
ProMPT_SetMotorVoltage(MOTORVOLTAGE);
ProMPT_SetLineVoltage(LINEVOLTAGE);
DS00861A-page 6
 2002 Microchip Technology Inc.
AN861
FIGURE 7:
APPLICATION FLOW CHART
Start
Initialization
Main Loop
Initialize Direction bits (TRIS)
to PORTA, PORTB and
PORTC
Is GO
bit = 0?
Service ADC
Set ADCON
GO bit
Update Display
Clear TMR0IF
Y
Initialize ProMPT Module
N
Set New VF Curve for the
Motor
Set:
Acceleration Rate,
Deceleration Rate,
Motor Voltage and
Input Line Voltage
IsTMR0IF
bit = 1?
Y
N
Is
ProMPTick = 1?
Button
pressed?
N
Y
Set Boost Parameters:
Boost Time, Boost Frequency,
Start, End % Modulation
and Enable Boost Mode
N
Y
Update
TargetTemp
Clear Fault bit
Update Motor
Frequency
Clear ProMPTick
Initialize Timer0
Set ADC 'GO' bit
 2002 Microchip Technology Inc.
DS00861A-page 7
AN861
DEVELOPMENT TOOL SETUP
Without the isolation transformer:
The following development tools were used to develop
this application:
1.
• MPLAB® IDE v6.10 or later version
• MPLAB® C18 C Compiler
• ProMPT™ Design Accelerator Kit with Single
Phase Induction Motor
• MPLAB® ICD 2 Programmer/Debugger
The MPLAB ICD 2 is connected to J4 for programming
the PIC18F2539 and to debug the program. The ICD 2
should be disconnected when the ProMPT drive is
powered from mains. Powering the ProMPT drive when
ICD 2 is connected will damage the ICD 2 or the computer connected to it, unless an isolation transformer is
used (see Figure 8).
Application development using the ICD 2 and ProMPT
MC Eval Board is simplified by using the isolation transformer. The following steps can be followed to develop
and debug an application program on the ProMPT MC
Eval Kit with an ICD 2.
Warning 1: Power electronics involve inherent risks,
both to equipment and personnel. This
document assumes that the user has
experience with high voltage electronics.
Incorrect use of the ProMPT drive can be
hazardous to development staff as well
as the user of the equipment.
2: Always disconnect the ProMPT drive
from power before making connections or
jumper settings. After switching off power,
wait until the “Power” LED is completely
off before working on the drive or motor.
Failure to comply with this warning could
result in injury or death.
DS00861A-page 8
Open a new project in MPLAB IDE v6.10 or
later.
2. Select MPLAB C18 C compiler as the tool suite.
3. Add the application program and header files to
the project.
4. Add the appropriate linker file to the project.
5. Compile and link the project.
6. With mains power disconnected from the
ProMPT MC Eval Board, connect MPLAB ICD 2
to J4 connector on the board.
7. Enable “Power target circuit from MPLAB ICD 2”
in menu programmer > settings > power.
8. Program the target chip and debug the application
code.
9. Disconnect MPLAB ICD 2.
10. Power up the ProMPT drive and continue testing.
With the isolation transformer:
1.
Open a new project in the MPLAB IDE v6.10 or
later.
2. Select MPLAB C18 C compiler as the tool suite.
3. Add the application program and header files to
the project.
4. Add the appropriate linker file to the project.
5. Compile and link the project.
6. Disable “Power target circuit from MPLAB
ICD 2” in menu programmer > settings > power.
MPLAB ICD 2 will be powered from the target
board.
7. With the MC Eval kit powered through an isolation transformer (see Figure 8), connect MPLAB
ICD 2 to the J4 connector on the board.
8. Program the target chip and debug the application
code.
9. If motor frequency is always ‘0’, or motor is left
disconnected, MPLAB ICD 2 may be left
connected during debugging.
10. To test motor operation, program the target chip
with Debug mode disabled, disconnect MPLAB
ICD 2, and continue testing.
 2002 Microchip Technology Inc.
AN861
FIGURE 8:
DEVELOPMENT TOOL SETUP WITH ISOLATION TRANSFORMER
Computer Running
MPLAB IDE
ICD 2
USB
Blower
J4
ICD 2
Power
Supply
Connect
computer,
ICD, and
isolation
transformer
to wall power.
J3
J2
ProMPT
Eval
Board
J1
Connect
oscilloscope
power to this
side of the
isolation
transformer.
Isolation
Transformer
To maintain isolation,
leave ground disconnected.
TABLE 1:
Note:
Even with the isolation transformer, the
ProMPT drive cannot be operated with
MPLAB ICD 2 connected. To operate the
motor (motor frequency greater than zero),
MPLAB
ICD 2
must
always
be
disconnected.
The advantage of the isolation setup shown in Figure 8
is that MPLAB ICD 2 or the computer will not be damaged if MPLAB ICD 2 is connected while the ProMPT
drive is powered up. This allows the user to step
through code and use other debugging features without
disconnecting the ProMPT board from the isolated AC
power. In addition, an oscilloscope can be used to look
at signals on the ProMPT board.
The jumpers, JP1-4 on the ProMPT board, should be
set to “INT” position to read the DC bus voltage
(VSENSE), motor current (ISENSE), heat sink
temperature (TSENSE) and clear the fault (/CLEAR).
 2002 Microchip Technology Inc.
Temp
Sensor
SUMMARY OF
MICROCONTROLLER
RESOURCE USE
Program Memory:
6184 Words (24%)
Data Memory:
41 bytes (3%)
Peripherals:
ADC
RA0 Temperature Sensor
Input
I/O Port Pins
RB4, RB5 Up and Down
Buttons
RA5, RC0, RC3 - RC7, LED Display Control
RB2, RB3
Timers
Timer0 used as a Delay
Timer for LED Multiplexing
SPIMC Kernel
Motor Control Functions
DS00861A-page 9
AN861
CONCLUSION
Variable speed control is easily added to an HVAC air
handler by using the ProMPT Single Phase Induction
Motor Control Evaluation Kit and the PIC18F2539
microcontroller. The Single Phase Induction Motor
Control kernel greatly simplifies the design of a single
phase induction motor control application. Microchip’s
Programmable Motor Processor Technology allows the
user to develop applications around the Single Phase
Induction Motor Control kernel with little or no
knowledge of motor control.
The PIC18F2539 microcontroller is suitable for control
of shaded pole and permanent magnet split capacitor
type motors. These types of AC single phase induction
motors are used in many household applications,
including HVAC, dishwashers, clothes washers and
dryers, garage door openers, lawn mowers, and so on.
ProMPT technology from Microchip has the potential to
greatly simplify design and reduce time-to-market for
all of these applications.
DS00861A-page 10
 2002 Microchip Technology Inc.
0.1nF
C1
10nF
C2
10nF
C3
 2002 Microchip Technology Inc.
RB5
4.7K
R2
4.7K
R10
R9
R8
R7
R6
R5
R4
R3
330
330
330
330
330
330
330
Q1
Q2
C6
0.1uF
10K
R14
+5V
C5
0.1uF
10K
R13
+5V
RB5
RB4
APPENDIX A:
RB4
10nF
C4
AN861
SCHEMATIC
DS00861A-page 11
4.7K
R12
4.7K
R11
AN861
Appendix B: ProMPT APPLICATION PROGRAM INTERFACE (API METHODS)
There are 27 separate API methods for the ProMPT kernel:
Note:
The operation of the Motor Control module and its APIs is based on an assumed clock frequency of 20 MHz.
Changing the oscillator frequency will change the timing used in the Motor Control module accordingly. To
achieve the best results in motor control applications, a clock frequency of 20 MHz is highly recommended.
void ProMPT_ClearTick(void)
Resources used: 0 stack levels
Description: This function clears the Tick (62.5 ms) timer flag returned by ProMPT_tick(). This function must be
called by any routine that is used for timing purposes.
void ProMPT_DisableBoostMode(void)
Resources used: 0 stack levels
Description: This function disables the Boost mode logic. This method should be called before changing any of the
Boost mode parameters.
void ProMPT_EnableBoostMode(void)
Resources used: 0 stack levels
Description: This function enables the Boost mode logic. Boost mode is entered when a stopped drive is commanded
to start. The drive will immediately go to Boost Frequency and ramp from Start Modulation to End Modulation over the
time period, Boost Time.
unsigned char ProMPT_GetAccelRate(void)
Resources used: 1 stack level
Range of values: 0 to 255
Description: Returns the current Acceleration Rate in Hz/second.
unsigned char ProMPT_GetBoostEndModulation(void)
Resources used: 1 stack level
Range of values: 0 to 200
Description: Returns the current End Modulation (in %) used in the Boost logic.
unsigned char ProMPT_GetBoostFrequency(void)
Resources used: 1 stack level
Range of values: 0 to 127
Description: Returns the current Boost Frequency in Hz.
unsigned char ProMPT_GetBoostStartModulation(void)
Resources used: 1 stack level
Range of values: 0 to BoostEndModulation
Description: Returns the Start Modulation (in %) used in the Boost logic.
DS00861A-page 12
 2002 Microchip Technology Inc.
AN861
unsigned char ProMPT_GetBoostTime()
Resources used: 1 stack level
Range of values: 0 to 255
Description: Returns the time in seconds for Boost mode.
unsigned char ProMPT_GetDecelRate()
Resources used: 1 stack level
Range of values: 0 to 255
Description: Returns the current Deceleration Rate in Hz/second.
unsigned char ProMPT_GetFrequency(void)
Resources used: 1 stack level
Range of values: 0 to 127
Description: Returns the current output frequency in Hz. This may not be the frequency commanded due to Boost or
Accel/Decel logic.
unsigned char ProMPT_GetModulation(void)
Resources used: Hardware Multiplier; 1 stack level
Range of values: 0 to 200
Description: Returns the current output modulation in %.
unsigned char ProMPT_GetParameter(unsigned char parameter)
Resources used: 1 stack level
Description: In addition to its pre-defined API methods, the ProMPT kernel allows the user to custom define up to 16
functions for control or communication purposes not covered by the ProMPT APIs. These parameters are used to communicate with motor control GUI evaluation tools, such as Microchip’s DashDriveMPTM. This method returns the current
value of any one of the parameters.
unsigned char ProMPT_GetVFCurve(unsigned char point)
Resources used: Hardware Multiplier; 1 stack level
Description: This function returns one of the 17 modulation values (in %) of the V/F curve. Each point represents a
frequency increment of 8 Hz, ranging from point 0 (0 Hz) to point 16 (128 Hz).
void ProMPT_Init(unsigned char PWMfrequency)
Resources used: 64 Bytes RAM; Timer2; PWM1 and PWM2; High Priority Interrupt Vector; Hardware Multiplier; fast
call/return; FSR 0; TBLPTR; 2 stack levels
PWMfrequency values: 0 or 1
Description: This function must be called before all other ProMPT methods, and it must be called only once. This
routine configures Timer2 and the PWM outputs.
When PWMfrequency is ‘0’, the module’s operating frequency is 9.75 kHz. When PWMfrequency is ‘1’, the module’s
operating frequency is 19.53 kHz.
Note:
Since the high priority interrupt is used, the fast call/return cannot be used by other routines.
 2002 Microchip Technology Inc.
DS00861A-page 13
AN861
void ProMPT_SetAccelRate(unsigned char rate)
Resources used: 0 stack level
rate range: 0 to 255
Description: Sets the acceleration to the value of rate in Hz/second. The default setting is 10 Hz/s.
void ProMPT_SetBoostEndModulation(unsigned char modulation)
Resources used: Hardware Multiplier; 0 stack levels
modulation range: 0 to 200
Description: Sets the End Modulation (in %) for the Boost logic. Boost mode operates at Boost Frequency, and the
modulation ramps from BoostStartModulation to BoostEndModulation. This function should not be called while
Boost is enabled.
unsigned char ProMPT_SetBoostFrequency(unsigned char frequency)
Resources used: 0 stack levels
frequency range: 0 to 127
Description: Sets the frequency the drive goes to in Boost mode. Frequency must be < 128. On exit, w = 0 if the
command is successful, or w = FFh if the frequency is out of range. This function should not be called while Boost is
enabled.
void ProMPT_SetBoostStartModulation(unsigned char modulation)
Resources used: Hardware Multiplier; 0 stack levels
modulation range: 0 to BoostEndModulation
Description: Sets the Start Modulation (in %) for the Boost logic. Boost mode operates at Boost Frequency, and the
modulation ramps from BoostStartModulation to BoostEndModulation. This function should not be called while
Boost is enabled.
void ProMPT_SetBoostTime(unsigned char time)
Resources used: Hardware Multiplier; 0 stack levels
time range: 0 to 255
Description: Sets the amount of time in seconds for the Boost mode. Boost mode operates at Boost Frequency, and
the modulation ramps from BoostStartModulation to BoostEndModulation over BoostTime. This function
should not be called while Boost is enabled.
void ProMPT_SetDecelRate(unsigned char rate)
Resources used: 0 stack levels
rate range: 0 to 255
Description: Sets the deceleration to the value of rate in Hz per second. The default setting is 5 Hz/s.
unsigned char ProMPT_SetFrequency(unsigned char frequency)
Resources used: 2 stack levels
frequency range: 0 to 127
Description: Sets the output frequency of the drive if the drive is running. Frequency is limited to 0 to 127, but should be
controlled within the valid operational range of the motor. Modulation is determined from the V/F curve, which is set up
with the ProMPT_SetVFCurve method. If frequency = 0, the drive will stop. If the drive is stopped and frequency > 0,
the drive will start.
DS00861A-page 14
 2002 Microchip Technology Inc.
AN861
void ProMPT_SetLineVoltage(unsigned char voltage)
Resources used: Hardware Multiplier; 0 stack levels
voltage range: 0 to 255
Description: Sets the line voltage for Automatic Voltage Compensation. The units for SetLineVoltage and
SetMotorVoltage must be the same for accurate operation. The values passed to SetMotorVoltage and
SetLineVoltage can be the same to disable voltage compensation.
void ProMPT_SetMotorVoltage(unsigned char voltage)
Resources used: Hardware Multiplier; 0 stack levels
voltage range: 0 to 255
Description: Sets the motor rating for Automatic Voltage Compensation. The units for SetLineVoltage and
SetMotorVoltage must be the same for accurate operation. The values passed to SetMotorVoltage and
SetLineVoltage can be the same to disable voltage compensation.
void ProMPT_SetParameter(unsigned char parameter, unsigned char value)
Resources used: 0 stack levels
parameter range:
Description: In addition to its pre-defined API methods, the ProMPT kernel allows the user to custom define up to 16
functions for control or communication purposes not covered by the ProMPT APIs. This function sets the value of the
specified user defined function.
void ProMPT_SetPWMfrequency(unsigned char PWMfrequency)
PWMfrequency values: 0 or 1
Resources used: Timer2; 1 stack level
Description: This sets and changes the PWM switching frequency. Typically, this is set with the Init() function. When
PWMfrequency is ‘0’, the module’s operating frequency is 9.75 kHz. When PWMfrequency is ‘1’, the module’s
operating frequency is 19.53 kHz.
void ProMPT_SetVFCurve(unsigned char point, unsigned char value)
Resources used: Hardware Multiplier; 0 stack level
point range: 0 to 16 (0 = 0 Hz, 1 = 8 Hz, 2 = 16 Hz……. 17 = 128 Hz)
value range: 0 to 200
Description: This sets one of the 17 modulation values (in %) for the V/F curve. Each point represents a frequency
increment of 8 Hz, ranging from point 0 (0 Hz) to point 16 (128 Hz).
unsigned char ProMPT_Tick(void)
Resources used: 1 stack level
Description: The value of the Tick timer flag becomes ‘1’ every 62.5 ms (1/16 second). This can be used for timing
applications. clearTick must be called in the timing routine when this is serviced.
 2002 Microchip Technology Inc.
DS00861A-page 15
AN861
APPENDIX C:
SOURCE CODE
Due to size considerations, the complete source code
for this application note is not included in the text. A
complete version of the source code, with all required
support files, is available for download as a Zip archive
from the Microchip web site at:
www.microchip.com
DS00861A-page 16
 2002 Microchip Technology Inc.
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Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
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Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
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Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
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Information contained in this publication regarding device
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assumed by Microchip Technology Incorporated with respect
to the accuracy or use of such information, or infringement of
patents or other intellectual property rights arising from such
use or otherwise. Use of Microchip’s products as critical components in life support systems is not authorized except with
express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, KEELOQ,
MPLAB, PIC, PICmicro, PICSTART and PRO MATE are
registered trademarks of Microchip Technology Incorporated
in the U.S.A. and other countries.
FilterLab, microID, MXDEV, MXLAB, PICMASTER, SEEVAL
and The Embedded Control Solutions Company are
registered trademarks of Microchip Technology Incorporated
in the U.S.A.
dsPIC, dsPICDEM.net, ECONOMONITOR, FanSense,
FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP,
ICEPIC, microPort, Migratable Memory, MPASM, MPLIB,
MPLINK, MPSIM, PICC, PICDEM, PICDEM.net, rfPIC, Select
Mode and Total Endurance are trademarks of Microchip
Technology Incorporated in the U.S.A. and other countries.
Serialized Quick Turn Programming (SQTP) is a service mark
of Microchip Technology Incorporated in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2002, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and Tempe, Arizona in July 1999
and Mountain View, California in March 2002.
The Company’s quality system processes and
procedures are QS-9000 compliant for its
PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals,
non-volatile memory and analog products. In
addition, Microchip’s quality system for the
design and manufacture of development
systems is ISO 9001 certified.
 2002 Microchip Technology Inc.
DS00861A - page 17
WORLDWIDE SALES AND SERVICE
AMERICAS
ASIA/PACIFIC
Corporate Office
Australia
2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: 480-792-7200 Fax: 480-792-7277
Technical Support: 480-792-7627
Web Address: http://www.microchip.com
Microchip Technology Australia Pty Ltd
Suite 22, 41 Rawson Street
Epping 2121, NSW
Australia
Tel: 61-2-9868-6733 Fax: 61-2-9868-6755
Rocky Mountain
China - Beijing
2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: 480-792-7966 Fax: 480-792-4338
Atlanta
3780 Mansell Road, Suite 130
Alpharetta, GA 30022
Tel: 770-640-0034 Fax: 770-640-0307
Boston
2 Lan Drive, Suite 120
Westford, MA 01886
Tel: 978-692-3848 Fax: 978-692-3821
Chicago
333 Pierce Road, Suite 180
Itasca, IL 60143
Tel: 630-285-0071 Fax: 630-285-0075
Dallas
4570 Westgrove Drive, Suite 160
Addison, TX 75001
Tel: 972-818-7423 Fax: 972-818-2924
Detroit
Tri-Atria Office Building
32255 Northwestern Highway, Suite 190
Farmington Hills, MI 48334
Tel: 248-538-2250 Fax: 248-538-2260
Kokomo
2767 S. Albright Road
Kokomo, Indiana 46902
Tel: 765-864-8360 Fax: 765-864-8387
Los Angeles
18201 Von Karman, Suite 1090
Irvine, CA 92612
Tel: 949-263-1888 Fax: 949-263-1338
San Jose
Microchip Technology Inc.
2107 North First Street, Suite 590
San Jose, CA 95131
Tel: 408-436-7950 Fax: 408-436-7955
Toronto
6285 Northam Drive, Suite 108
Mississauga, Ontario L4V 1X5, Canada
Tel: 905-673-0699 Fax: 905-673-6509
Microchip Technology Consulting (Shanghai)
Co., Ltd., Beijing Liaison Office
Unit 915
Bei Hai Wan Tai Bldg.
No. 6 Chaoyangmen Beidajie
Beijing, 100027, No. China
Tel: 86-10-85282100 Fax: 86-10-85282104
China - Chengdu
Microchip Technology Consulting (Shanghai)
Co., Ltd., Chengdu Liaison Office
Rm. 2401-2402, 24th Floor,
Ming Xing Financial Tower
No. 88 TIDU Street
Chengdu 610016, China
Tel: 86-28-86766200 Fax: 86-28-86766599
China - Fuzhou
Microchip Technology Consulting (Shanghai)
Co., Ltd., Fuzhou Liaison Office
Unit 28F, World Trade Plaza
No. 71 Wusi Road
Fuzhou 350001, China
Tel: 86-591-7503506 Fax: 86-591-7503521
China - Hong Kong SAR
Microchip Technology Hongkong Ltd.
Unit 901-6, Tower 2, Metroplaza
223 Hing Fong Road
Kwai Fong, N.T., Hong Kong
Tel: 852-2401-1200 Fax: 852-2401-3431
China - Shanghai
Microchip Technology Consulting (Shanghai)
Co., Ltd.
Room 701, Bldg. B
Far East International Plaza
No. 317 Xian Xia Road
Shanghai, 200051
Tel: 86-21-6275-5700 Fax: 86-21-6275-5060
China - Shenzhen
Microchip Technology Consulting (Shanghai)
Co., Ltd., Shenzhen Liaison Office
Rm. 1812, 18/F, Building A, United Plaza
No. 5022 Binhe Road, Futian District
Shenzhen 518033, China
Tel: 86-755-82901380 Fax: 86-755-82966626
China - Qingdao
Rm. B503, Fullhope Plaza,
No. 12 Hong Kong Central Rd.
Qingdao 266071, China
Tel: 86-532-5027355 Fax: 86-532-5027205
India
Microchip Technology Inc.
India Liaison Office
Divyasree Chambers
1 Floor, Wing A (A3/A4)
No. 11, O’Shaugnessey Road
Bangalore, 560 025, India
Tel: 91-80-2290061 Fax: 91-80-2290062
Japan
Microchip Technology Japan K.K.
Benex S-1 6F
3-18-20, Shinyokohama
Kohoku-Ku, Yokohama-shi
Kanagawa, 222-0033, Japan
Tel: 81-45-471- 6166 Fax: 81-45-471-6122
Korea
Microchip Technology Korea
168-1, Youngbo Bldg. 3 Floor
Samsung-Dong, Kangnam-Ku
Seoul, Korea 135-882
Tel: 82-2-554-7200 Fax: 82-2-558-5934
Singapore
Microchip Technology Singapore Pte Ltd.
200 Middle Road
#07-02 Prime Centre
Singapore, 188980
Tel: 65-6334-8870 Fax: 65-6334-8850
Taiwan
Microchip Technology (Barbados) Inc.,
Taiwan Branch
11F-3, No. 207
Tung Hua North Road
Taipei, 105, Taiwan
Tel: 886-2-2717-7175 Fax: 886-2-2545-0139
EUROPE
Austria
Microchip Technology Austria GmbH
Durisolstrasse 2
A-4600 Wels
Austria
Tel: 43-7242-2244-399
Fax: 43-7242-2244-393
Denmark
Microchip Technology Nordic ApS
Regus Business Centre
Lautrup hoj 1-3
Ballerup DK-2750 Denmark
Tel: 45 4420 9895 Fax: 45 4420 9910
France
Microchip Technology SARL
Parc d’Activite du Moulin de Massy
43 Rue du Saule Trapu
Batiment A - ler Etage
91300 Massy, France
Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79
Germany
Microchip Technology GmbH
Steinheilstrasse 10
D-85737 Ismaning, Germany
Tel: 49-89-627-144 0 Fax: 49-89-627-144-44
Italy
Microchip Technology SRL
Centro Direzionale Colleoni
Palazzo Taurus 1 V. Le Colleoni 1
20041 Agrate Brianza
Milan, Italy
Tel: 39-039-65791-1 Fax: 39-039-6899883
United Kingdom
Microchip Ltd.
505 Eskdale Road
Winnersh Triangle
Wokingham
Berkshire, England RG41 5TU
Tel: 44 118 921 5869 Fax: 44-118 921-5820
12/05/02
DS00861A-page 18
 2002 Microchip Technology Inc.
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