Note the following details of the code protection feature on Microchip devices:
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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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INTRODUCTION
This chapter contains general information that will be useful to know before using the
Humidity Sensor PICtail™ Demo Board. Items discussed in this chapter include:
• Document Layout
• Conventions Used in this Guide
• Recommended Reading
• The Microchip Web Site
• Customer Support
• Document Revision History
DOCUMENT LAYOUT
This document describes how to use the Humidity Sensor PICtail™ Demo Board as a
development tool to emulate and debug firmware on a target board. The manual layout
is as follows:
• Chapter 1. “Product Overview” – This is an introduction to the Humidity Sensor
PICtail™ Demo Board. It covers the kit contents, associated tools and how they
work together.
• Chapter 2. “Setup and Installation” – Covers the initial set-up of the Humidity
Sensor PICtail™ Demo Board. It lists the required tools, shows how to connect
this board and demonstates how to verify the set-up.
• Chapter 3. “Operation” – This chapter discusses using the humidity sensor on
the PCB and using the software PC Application.
• Chapter 4. “Modified Circuit” – Gives the modifications necessary to increase
measurement resolution by a factor of 100 (see AN1016 for details)
• Appendix A. “Schematic and Layouts” – Gives detailed information on the
Humidity Sensor PICtail™ Demo Board. Includes detailed circuit explanation,
schematic and board layouts.
• Appendix B. “Bill Of Materials (BOM)” – Gives detailed information on the
This user's guide describes how to use Humidity Sensor PICtail™ Demo Board. Other
useful documents are listed below and are recommended as supplemental reference
resources.
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
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
• Distributor or Representative
• Local Sales Office
• Field Application Engineer (FAE)
• Technical Support
• Development Systems Information Line
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://support.microchip.com
The Printed Circuit Board (PCB) discussed in this user’s guide is described as follows:
HUMIDITY SENSOR PICTAIL™
DEMO BOARD USER’S GUIDE
• Order Number:
• Assembly Number:
•Board Name:
This board supports the capacitive humidity sensor application note AN1016. It
measures the capacitance of a relative humidity sensor (or capacitor) plugged into the
board. The on-board microcontroller sends the measured and calculated data to a PC
(Personal Computer) for display.
Items discussed in this chapter include:
• Kit Contents
• Humidity Sensor PICtail™ Demo Board
• Associated Tools
• Initial Set-up
1.2KIT CONTENTS
• Humidity Sensor PICtail™ Demo Board – This is an assembled and tested
Printed Circuit Board (PCB).
• CD-ROM – Provided separately in the shipping box; it contains the files and
literature mentioned in this user’s guide.
• Humidity Sensor (HS1101LF) – Provided separately in the shipping box.
• Bag of Capacitors – Provided separately in the shipping box. These capacitors
are provided for the user’s convenience; they make it easy to try out this board’s
functionality, and to verify its accuracy.
The circuit operation is detailed in AN1016, “Detecting Small Capacitive Sensors Using
the MCP6291 and PIC16F690 Devices” (DS01016)
The Humidity Sensor PICtail™ Demo Board contains the circuitry represented in
Figure 1-1. The ambient relative humidity changes the capacitance of the humidity
sensor (HS1101LF from Humirel). This sensor is connected to a MCP6291 op amp and
a resistor to form an inverting (Miller) integrator. The PIC16F690 microcontroller sends
a square wave to the input of the integrator, which the integrator converts to a triangle
wave at its output. The firmware controls the magnitude of the triangle wave and
measures the integration time. The microcontroller measures the time it takes for the
triangle wave to rise and fall. These times are converted to a capacitance value.
A 14-pin header is provided for connecting to the PICkit™ 1 Flash Starter Kit, which
acts like a docking station. It includes a two-wire serial bus that transfers the data, and
two more wires for board power (+5V and GND inputs). This interface also supports
programming of the on-board PIC16F690.
The +5V single supply voltage from the PICkit™ 1 Flash Starter Kit board is bypassed
with two bulk 1 μF capacitors near the header, and two local 0.1 μF capacitors (one for
each Integrated Circuit (IC)).
A 6-pin header for ICSP™ (In-Circuit Serial Programming™) is available as an alternate
interface for programming the on-board PIC16F690. This allows the user to modify the
program that comes with the Humidity Sensor PICtail™ Demo Board (with the MPLAB
ICD 2 or PICkit™ 2 microcontroller programmer).
The test points make it easier to test key points in the circuit using common lab
equipment. The test points are:
• GND – Is connected to ground plane, and is for any lab equipment
• +5V – Positive supply voltage (at board edge); it provides a means to power this
board with a laboratory power supply (when not connected to the PICkit™ 1 Flash
Starter Kit)
•V
INT – Integrator’s input (a square wave during measurements)
CM – Op amp’s common mode voltage (at its inverting input)
•V
•V
SEN – Integrator’s output of the integrator (a triangle wave during
measurements)
More details on the circuit and on its design can be found in Appendix A. “Schematic and Layouts” and AN1016, “Detecting Small Capacitive Sensors Using the MCP6291
and PIC16F690 Devices” (DS01016).
Figure 1-2 shows the block diagram of the hardware and software tools that the
Humidity Sensor PICtail™ Demo Board is designed to work with. More information on
these tools can be found in the “Recommended Reading” section.
Product Overview
HardwareSoftware
PC
USB
PICkit™ 1
Flash Starter Kit
14
Humidity Sensor
PICtail™ Demo Board
6
ICSP™
Capacitance.exe
PC Program
PICkit™ 1
Firmware
00084R1.hex
Firmware
FIGURE 1-2:Measurement Set-up Block Diagram.
1.4.1Humidity Sensor PICtail™ Demo Board
This board is described in Section 1.3 “Humidity Sensor PICtail™ Demo Board”.
1.4.2Firmware for the Humidity Sensor PICtail™ Demo Board
00084R1.hex is the firmware file that supports the Humidity Sensor PICtail™ Demo
Board application. It implements the measurement routines and the data
communications with the PICkit™ 1 Flash Starter Kit.
1.4.3ICSP™ Header
The ICSP header provides a means to program the PIC16F690. It is intended for
connection to devices that program the on board PIC16F690, such as the MPLAB
®
ICD 2 (DV164005) and the PICkit™ 2 Microcontroller Programmer (DV164120).
1.4.4PICkit™ 1 Flash Starter Kit
The PICkit 1 Flash Starter Kit (DV164101) programs PICmicro® microcontrollers. It is
used to program the PIC16F690, and provides a communications link with the PC. The
PICkit™ 1 Flash Starter Kit’s PIC16C745 has a USB port that communicates with the
Humidity Sensor PC Program. It also connects to the Humidity Sensor PICtail™ Demo
Board (the on-board PIC16F690) via a header (see Figure 2-1).
This board provides a single +5V supply voltage for the daughter board. It can drive up
to 5 μF on the supply; a larger capacitance may interfere with program timing.
1.4.5PICkit™ 1 Firmware
This software resides on the PICkit™ 1 Flash Starter Kit’s PIC16C745 microcontroller.
Use version 2.0.2 or later.
The Personal Computer (PC) shown in Figure 1-2 needs to run on Windows®98 SE or
later. It provides a convenient interface for the user, communicates with the other
boards and provides power through the USB connection.
1.4.7Humidity Sensor PC Program
The capacitance.exe PC Program communicates with the PIC16F690 MCU on the
Humidity Sensor PICtail™ Demo Board through the USB port on the PICkit™ 1 Flash
Starter Kit. It also imports data through the same connections and displays them.
The user inputs the board configuration, and can select to view either capacitance or
relative humidity (assuming the HS1101LF sensor is plugged in).
1.5ASSEMBLY CODE MODULES
The following assembly code modules (for the PIC16F690) make up the Humidity
Sensor project:
• main.inc - contains I/O port and global defines used throughout the project
• main.asm - contains the main executive routine including configuration bit
assignments
• initialize_f690.asm - initializes the PIC16F690 to known initial values
• capacitance.asm - reads capacitance using a dual slope integration technique
• humidity.asm - contains PwLI routine to convert capacitance to %RH humidity
• ssc.asm - contains Synchronous Serial Communications (SSC), which is a
synchronous serial communications protocol between a target PICmicro
controller (MCU) and the PICkit™ 1 Flash Starter Kit or PICkit™ 2 Starter Kit
• 16f690.lkr - linker script for Humidity Sensor project
These files can be downloaded from the Microchip web site (www.microchip.com) and
are contained in the “00084R1.zip” file.
This chapter shows how to set up the Humidity Sensor PICtail™ Demo Board. Items
discussed in this chapter include:
• Required Tools
• Connecting the Humidity Sensor PICtail™ Demo Board
• Set-up Verification
2.2REQUIRED TOOLS
The PICkit™ 1 Flash Starter Kit User’s Guide explains how to set up the PC and the
PICkit™ 1 Flash Starter Kit. Use firmware version 2.0.2 or later.
The PICkit™ 1 Flash Starter Kit CD-ROM (DS40049) contains many of the necessary
files.
The capacitance.exe PC program comes with the Humidity Sensor PICtail™ Demo
Board CD-ROM (Version v1.07.01 or later).
HUMIDITY SENSOR PICTAIL™
DEMO BOARD USER’S GUIDE
2.3SETTING UP THE HUMIDITY SENSOR PICTAIL™ DEMO BOARD
This section discusses the primary method for setting up the Humidity Sensor PICtail™
Demo Board. An exploded view of how the different boards connect is shown in
Figure 2-1.
ICSP™ Header
USB Cable
Expansion
Header (J3)
To PC
PIC16C745 Firmware
Version 2.0.2 or later
FIGURE 2-1:Board Connections for PICkit™ 1 Flash Starter Kit.
1. Remove any PICmicro microcontroller that may be in the Evaluation Socket.
2. Connect the USB cable to the PC and to the PICkit™ 1 Flash Starter Kit board.
The status LEDs (green POWER and yellow BUSY in the LED array) should light
up.
It is easiest to use this board when it lays directly on a bench top.
2.3.2Humidity Sensor PICtail™ Demo Board
1. Setup Board (first time only); connect shunt to jumper JP1 at the 0.1 pF / position
(0.1 pF / count).
2. Plug this board into the PICkit 1 Flash Starter Kit’s expansion header J3 (as
shown in Figure 2-1) without covering the LED array. There should be no change
in the status LEDs on the PICkit™ 1 Flash Starter Kit board after it is plugged in.
The PIC16F690 comes with the 00084R1.hex file already programmed.
2.3.3Humidity Sensor PC Program
1. Run the installer program, AN1016 install.exe (which places the executable
file capacitance.exe in the desired directory).
2. Run the capacitance.exe PC Program to start the Graphical User Interface
(GUI).
2.3.4Set-up Verification
1. Check Basic Functionality.
a) Place one of the capacitors that came in the shipping box (nominal values of
10 pF, 180 pF, 1.0 nF and 100 nF) into the Csen socket.
b) Follow the steps 1.a. through 1.g. in Section 3.3 “Using the Humidity
Sensor PC Program”.
c) The reading should be within ±5% (for 10 pF, 180 pF, and 1.0 nF capacitors),
or ±10% (for the 100 nF capacitor only), of the nominal value.
2. Check HS1101LF Sensor.
a) Place the HS1101LF sensor into the Csen socket.
b) Follow the steps 2.a. through 2.f. in Section 3.3 “Using the Humidity
Sensor PC Program”.
c) The reading should be similar to that of a calibrated relative humidity sensor
An exploded view of how the PICkit™ 2 microcontroller programmer connects to the
Humidity Sensor PICtail™ Demo Board is shown in Figure 2-2. This setup is an
alternative way to reprogram the PIC16F690 on the Humidity Sensor PICtail™ Demo
Board.
USB Cable
Setup and Installation
To PC
ICSP™ Header (P2)
PICkit™ 2 Microcontroller Programmer
Humidity Sensor
PICtail™ Demo Board
FIGURE 2-2:Board Connections for PICkit™ 2 Microcontroller Programmer.
2.4.2MPLAB® ICD 2
An exploded view of how the MPLAB® ICD 2 connects to the Humidity Sensor
PICtail™ Demo Board is shown in Figure 2-3. This setup is an alternative way to
reprogram the PIC16F690 on the Humidity Sensor PICtail™ Demo Board.
This demonstration board makes it easy to explore the operation of a humidity sensor
application. Items discussed in this chapter include:
• Configuring the Humidity Sensor PICtail™ Demo Board
• Using the Humidity Sensor PC Program
• Programming the PIC16F690
• Humidity Sensor Calibration
3.2CONFIGURING THE HUMIDITY SENSOR PICTAIL™ DEMO BOARD
1. Setup the board as explained in Chapter 2. “Setup and Installation”.
2. Place a humidity sensor or capacitor in the C
a) Humirel’s HS1101LF capacitive humidity sensor.
b) A capacitor of known value.
3. Connect the shunt to jumpers JP1 – JP3 according to the measurement
resolution and capacitance values desired; see Table 3-1.
4. Allow sufficient time for the humidity sensor to respond to changes in the
environment (about 30 seconds for the HS1101LF).
SEN
socket.
TABLE 3-1:JUMPER SELECTION – MODIFIED CIRCUIT
Jumper
Selected
JP10.10.6 pF to 6.5 nF6.65 M Use for HS1101LF sensor
JP216 pF to 65 nF665 k
JP31060pF to 650nF66.5k
Measurement
Resolution
(pF / count)
C
SEN
Range
3.3USING THE HUMIDITY SENSOR PC PROGRAM
The capacitance.exe PC Program Graphical User Interface (GUI) is displayed in
Figure 3-1. It is a simple program that helps the user to control the functionality of the
Humidity Sensor PICtail™ Demo Board and to view the results sent back from that
board.
Note:This program is intended as an evaluation tool; it does not check for all
possible errors. It is the user’s responsibility to make sure the GUI and
demo board are used under reasonable conditions.
The following steps will help familiarize the user with this GUI. The step numbers are
displayed in Figure 3-1.
1. Measure Capacitance (C
a) Put capacitor in C
SEN
).
SEN
’s socket on the board.
b) Select desired resolution on the board (set by shunt and JP1 – JP3).
c) Input the resolution.
d) Click on the READ CAPACITANCE button.
e) The green light turns on and the status window is updated.
f)Read the current capacitance value (which is updated about once a second).
g) Click on the STOP READING button.
2. Measure Humidity (RH).
a) Put the HS1101LF sensor in C
’s socket on the board.
SEN
b) Select the 0.1 pF / count resolution on the board (put shunt across JP1).
c) Click on the READ HUMIDITY button (a resolution of 0.1 pF / count is assumed
by the GUI).
d) The green lights turn on and the status window is updated.
e) Read the current capacitance value and relative humidity (which are updated
about once a second).
f)Click on the STOP READING button.
3. Check Program Status.
a) Read the status history in the status window.
b) Click the CLEAR STATUS WINDOW button to clear the status history.
c) Click the FIRMWARE VERSION button to see the version displayed in the status
window.
4. Quit the Program.
a) Click the FILE button, then the EXIT button that pops up. Or click on the
If desired, the capacitive humidity sensor used on this board can be calibrated. Manufacturing tolerances, aging and changes in circuit operating conditions (i.e., supply
voltage and temperature) may cause errors larger than desired. Many reputable
companies provide humidity calibration equipment and/or services.
There are two common approaches to calibrating these sensors:
1. Put sensor in an atmosphere with well controlled RH.
2. Use another, more accurate sensor to measure the RH.
In both cases, there are two areas of concern. First, the RH can change rapidly across
time and position, making an accurate calibration difficult to do. Second, it takes time
for humidity sensors to settle to an accurate value. Some can take many minutes to
settle properly.
The modifications described here will reduce the current going into the integrator (I
by a factor of 100 ×, so the measurement resolution increases by the same factor.
These modifications are intended for measuring small capacitances. See AN1016 for
more details on this modified circuit’s performance.
4.2THE “REDUCED CURRENT” CIRCUIT
4.2.1Modifications
Figure 4-1 shows the Humidity Sensor PICtail™ Demo Board top silk-screen.
Figure 4-1 also shows the locations of the resistors that need to be modified to
implement the “Reduced Current” circuit discussed in application note AN1016:
1. Remove (de-solder) the 1Ω resistor, RA1, already on the board.
2. Refer to Appendix B. “Bill Of Materials (BOM)”, Section B.3 for the BOM for
the three resistors (provided by the user) that need to be soldered onto the board.
Configure the Humidity Sensor PICtail™ Demo Board as follows:
1. Start with the configuration in Section 3.2.
2. Connect the shunt to jumpers JP1 – JP3 according to the modified measurement
resolutions and capacitance values desired; see Table 4-1.
TABLE 4-1:JUMPER SELECTION – MODIFIED CIRCUIT
Jumper
Selected
JP10.0010.6 pF to 65 pF6.65 M
JP20.016 pF to 650 pF665 k
JP30.160 pF to 6.5 nF66.5 k
4.2.3Interpreting the Output from the Humidity Sensor PC Program
The capacitance.exe PC program displays measured capacitance values assuming
the Humidity Sensor PICtail™ Demo Board has not been modified. To correct the displayed values, move the displayed decimal point to the left two places (e.g., 321.0 pF is
actually 3.210 pF).
Measurement Resolution
(pF / count)
C
SEN
Range
R
INT
(Ω)
Note:The decimal point must be moved two places to the left by the user for the
modified circuit.
The RH numbers make no sense for measurements produced by the modified board;
they are based on another circuit configuration (see Section 3.2).
This appendix contains the schematics and layouts for the Humidity Sensor PICtail™
Demo Board.
A.2HIGHLIGHTS
The Humidity Sensor PICtail™ Demo Board is constructed using a two-layer Printed
Circuit Board (PCB). The top layer is for components and traces. The bottom layer is
the ground plane.
Information on this board includes:
• Board Schematic
• Board – Top Silk-screen
• Board – Top Metal Layer
• Board – Bottom Metal Layer
HUMIDITY SENSOR PICTAIL™
DEMO BOARD USER’S GUIDE
A.3DEMONSTRATION BOARD DESCRIPTION
A schematic is shown in Figure A-1 and Figure A-2. Csen is the humidity sensor or
capacitor. Op amp, U2, and the components, Csen and R
form an inverting (Miller) integrator. The jumpers, JP1 – JP3, select the R
choice (6.65 MΩ, 665 kΩ or 66.5 kΩ), which sets the measurement resolution
(0.1 pF / count, 1 pF / count or 10 pF / count). The microcontroller, U1, sends a square
wave at its pin 14 to the input of the integrator. The integrator converts it to a triangle
wave, which is seen at the microcontroller’s pin 15. There is a comparator internal to
U1 which compares the voltage at pin 15 to one of two reference levels; V
V
or VRH= 0.500 VDD. The microcontroller changes the logic value output at pin 14
DD
each time the triangle wave exceeds one of these two limits.
The microcontroller (U1) measures the time between changes in logic values at pin 14
(“integration times”), and calculates a capacitance value for Csen. This capacitance
value (C
sensor. C
them to the capacitance.exe PC program on the PC via the USB cable.
Note:Converting Csen to RH for other humidity sensors must be done either
RA1 – RA3 are used for the “Op Amp Integrator with Reduced Current” described in
AN1016 and Chapter 4. “Modified Circuit”. Rcm1, Rcm2 and Ccm provide a
mid-supply reference voltage for the op amp, U2.
) is converted to Relative Humidity (RH) for Humirel’s HS1101LF humidity
SEN
and RH are then sent to the PICkit™ 1 Flash Starter Kit, which sends
SEN
manually or by modifying the PIC16F690 firmware (i.e., the linear
interpolation table).
The test points, TP3 – TP5, have 10 kΩ placed in series to isolate the circuit from
external measurement equipment. This will help prevent over-voltage events, and will
help the op amp, U2, operate in a stable condition.
a) This is a two-layer board. It has a solid ground plane on the bottom layer to
minimize EMC issues, and routes the traces in the top layer. The complete
schematic is in Figure A-1 and Figure A-2, the board layer plots in Figure A-3,
Figure A-4 and Figure A-5. The Bill of Materials (BOM) is in Appendix B. “Bill Of Materials (BOM)”. The Gerber files for this board are available on
the Microchip web site (www.microchip.com) and are contained in the zip file
00084R1.zip.
A.4THE “REDUCED CURRENT” MODIFICATION
Figure A-1 shows the Humidity Sensor PICtail™ Demo Board as it comes from
Microchip. This board can be modified by the user to implement the “Reduced Current”
circuit discussed in application note AN1016 and Chapter 4. “Modified Circuit”.
A.5ADDITIONAL COMMENTS
The demonstration board includes test points for convenience on the bench. The “+5V”
and “GND” test points (TP1 and TP2) connect to the board’s supply voltages.
Note:Do NOT connect a power supply to the “+5V” and “GND” test points, unless
the board is NOT connected to the PICkit™ 1 Flash Starter Kit (i.e., it
stands alone).
The “V
square wave into the integrator. The “V
the op amp’s common mode input voltage. The “V
tion to the op amps output to allow the user to monitor the triangle wave at the integrator’s output.
The PICkit™ 1 Flash Starter Kit provides a +5V single supply voltage. It can drive up to
5 μF on the supply; a larger capacitive load causes current loading and timing issues.
This demonstration board also uses the +5V single supply voltage. It has two 1 μF bulk
bypass capacitors and two 0.1 μF local bypass capacitors.
High frequency design practices are used to minimize digital interference:
• Solid ground plane
• Surface mount devices for the analog circuitry
• Separate digital and analog lines and sections
INT” test point (TP3) connects to U1’s pin 14 to allow the user to monitor the
B.2BOM FOR HUMIDITY SENSOR AND OTHER CAPACITORS IN BOX
Table B-2 lists capacitors included separately in the Humidity Sensor PICtail™ Demo
Board’s shipping box. These capacitors or the HS1101LF sensor will fit in the Csen pin
recepticles. The capacitors provide a means for quickly evaluating circuit operation.
TABLE B-2:BILL OF MATERIALS FOR HUMIDITY SENSOR AND OTHER CAPACITORS