Microchip Technology MCP355X Sensor Application Developer’s Board User guide

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MCP355X

Sensor Application

Developer’s Board

User’s Guide

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MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Table of Contents

Preface ........................................................................................................................... 1

Introduction............................................................................................................ 1

Document Layout .................................................................................................. 1

Conventions Used in this Guide ............................................................................ 2

Recommended Reading........................................................................................ 2

The Microchip Web Site ........................................................................................ 3

Customer Support ................................................................................................. 3

Document Revision History ................................................................................... 3

Chapter 1. Product Overview ....................................................................................... 5

1.1 Introduction ..................................................................................................... 5

1.2 What is the MCP355X Sensor Application Developer’s Board? .................... 5

1.3 What the MCP355X Sensor Application Developer’s Board Kit Includes ...... 6

Chapter 2. Hardware Description ................................................................................ 7

2.1 Overview ........................................................................................................ 7

2.2 Sensor Input Connections .............................................................................. 8

2.3 Channel 1 - Low-Cost Differential Gain Circuit Using MCP6XX Amplifier ...... 9

2.4 Channel 2 - High-Precision Gain Circuit ....................................................... 11

2.5 Bridge Simulator Boards .............................................................................. 12

Chapter 3. Firmware Description ............................................................................... 13

3.1 Firmware Overview ...................................................................................... 13

3.2 PIC16F877 ................................................................................................... 13

3.3 PIC18F4550 ................................................................................................. 16

Chapter 4. DataView .................................................................................................... 17

4.1 Overview ...................................................................................................... 17

4.2 Scope Plot Window ...................................................................................... 17

4.3 Noise Histogram Window ............................................................................. 18

4.4 Auxiliary Data Window ................................................................................. 18

4.5 Configuring DataView ................................................................................... 19

MCP355X Sensor Application Developer’s Board User’s Guide

Appendix A. Schematic and Layouts ........................................................................21

A.1 Introduction .................................................................................................. 21

A.2 Schematic - Page 1 .................................................................................... 22

A.3 Schematic - Page 2 .................................................................................... 23

A.4 Schematic - Page 3 .................................................................................... 24

A.5 Schematic - Bridge Simulator ..................................................................... 25

A.6 Board Layout - Top Layer and Silk Screen .............................................. 26

A.7 Board Layout - Top Layer .......................................................................... 26

A.8 Board Layout - Bottom Layer and Silk Screen ......................................... 27

A.9 Board Layout - Bottom Layer ..................................................................... 27

A.10 Board Layout - Bridge Simulator .............................................................. 28

Appendix B. Bill Of Materials (BOM) ..........................................................................29

Worldwide Sales and Service .....................................................................................32

MCP355X SENSOR APPLICATION

DEVELOPER’S 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.

INTRODUCTION

This chapter contains general information that will be useful to know before using the MCP355X Sensor Application Developer’s 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 MCP355X Sensor Application Developer’s Board as a development tool. The manual layout is as follows:

• Chapter 1. “Product Overview” – Important information about the MCP355X Sensor Application Developer’s Board.

• Chapter 2. “Hardware Description”– Includes detailed description of the hardware for the MCP355X Sensor Application Developer’s Board.

• Chapter 3. “Firmware Description” – Includes detailed description of the software for the MCP355X Sensor Application Developer’s Board.

• Chapter 4. “DataView” - Includes detail description of the DataView software.

• Appendix A. “Schematic and Layouts” – Shows the schematic and layout diagrams for the MCP355X Sensor Application Developer’s Board.

• Appendix B. “Bill Of Materials (BOM)” – Lists the parts used to build the MCP355X Sensor Application Developer’s Board

MCP355X Sensor Application Developer’s Board User’s Guide

CONVENTIONS USED IN THIS GUIDE

This manual uses the following documentation conventions:

DOCUMENTATION CONVENTIONS

Description Represents Examples

Arial font:

Italic characters Referenced books MPLAB® IDE User’s Guide

Emphasized text ...is the only compiler...

Initial caps A window the Output window

A dialog the Settings dialog A menu selection select Enable Programmer

Quotes A field name in a window or

dialog

Underlined, italic text with right angle bracket

Bold characters A dialog button Click OK

N‘Rnnnn A number in verilog format,

Text in angle brackets < > A key on the keyboard Press <Enter>, <F1>

Courier New font:

Plain Courier New Sample source code #define START

Italic Courier New A variable argument file.o, where file can be

Square brackets [ ] Optional arguments mcc18 [options] file

Curly brackets and pipe character: { | }

Ellipses... Replaces repeated text var_name [,

A menu path File>Save

A tab Click the Power tab

where N is the total number of digits, R is the radix and n is a digit.

Filenames autoexec.bat File paths c:\mcc18\h Keywords _asm, _endasm, static Command-line options -Opa+, -Opa- Bit values 0, 1 Constants 0xFF, ‘A’

Choice of mutually exclusive arguments; an OR selection

Represents code supplied by user

“Save project before build”

4‘b0010, 2‘hF1

any valid filename

[options]

errorlevel {0|1}

var_name...]

void main (void) { ... }

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

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 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

Preface

DOCUMENT REVISION HISTORY

Revision A (June 2006)

• Initial Release of this Document.

MCP355X Sensor Application Developer’s Board User’s Guide

NOTES:

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Chapter 1. Product Overview

1.1 INTRODUCTION

This chapter provides an overview of the MCP355X Sensor Application Developer’s Board and covers the following topics:

• What is the MCP355X Sensor Application Developer’s Board?

• What the MCP355X Sensor Application Developer’s Board Kit includes

1.2 WHAT IS THE MCP355X SENSOR APPLICATION DEVELOPER’S BOARD?

The MCP355X Sensor Application Developer’s Board allows for easy system design of high resolution systems such as weigh scale, temperature sensing, or other small signal systems requiring precise signal conditioning circuits. The reference design includes firmware that performs all the necessary functions including ADC sampling, USB communication for PC data analysis, LCD display output, zero cancellation, full scale calibration, and units display in gram (g), kilogram (kg), or ADC output units. Figure 1-1 shows the LCD display output in kg of a high resolution system.

FIGURE 1-1: MCP355X Sensor Application Developer’s Board LCD showing weigh scale output in kilograms.

Reference Design Features:

• Signal Conditioning Circuit Selection and Gain Selection

• Voltage Reference Selection

•PICmicro

• Preprogrammed LCD firmware for ADC Output in g, kg or system code

• DataView USB connection for easy PC evaluation of system error

• High Resolution System Board Design

microcontroller sockets and LCD for firmware development on-board

MCP355X Sensor Application Developer’s Board User’s Guide

1.3 WHAT THE MCP355X SENSOR APPLICATION DEVELOPER’S BOARD KIT INCLUDES

This MCP355X Sensor Application Developer’s Board Kit includes:

• The MCP355X Sensor Application Developer’s Board, 102-00090

• MCP355X Sensor Application Developer’s Board User’s Guide (DS-51609)

• MCP3550/1/3 Data Sheet, “Low-Power Single Channel 22-Bit Delta Sigma ADCs” (DS21950)

• AN1030, “Weigh Scale Applications for the MCP3551” (DS01030)

2.1 OVERVIEW

The MCP355X Sensor Application Developer’s Board’s purpose is to ease development of small signal sensor MCP355X applications such as weigh scales. There are two circuits, or channels, to allow for comparison of different approaches to signal conditioning circuits. The first channel is a low-cost, low-power signal conditioning circuit that uses Microchip’s MCP6XX amplifiers. This circuit is intended to be a reference design for low power, low cost MCP355X applications requiring intermediate ranges of signal gain.

The second channel uses a precision amplifier with high gain. It is intended to be a reference design for MCP355X circuits that can require higher resolution.

The board has jumper connections and screw terminals to connect external sensors such as load cells or RTD temperature sensors. The board easily accomodates both 4-wire and 6-wire load cells sensor connections.

The system includes two PICmicro MCUs for firmware development and data analysis through either an LCD display or graphically on a PC using a USB connection. A PIC16F877 communicates with the two MCP355X channels, push-buttons and LCD display.

For data analysis on the PC the USB PIC18F4550 is used. This device collects the post processed PIC16F877 data and passes it via USB to the PC for display on DataView software.

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Chapter 2. Hardware Description

USB to PC running DataView

PIC18F4550

PIC16F877

FIGURE 2-1: MCP355X Sensor Application Developer’s Board Functional Block Diagram and Results.

MCP3551 ΔΣ

SPI

MCP3551 ΔΣ

LCD Display

Push Button Control Switches

ADC

CHANNEL 1

ADC

CHANNEL 2

GAIN

Sensor Input Connections

MCP355X Sensor Application Developer’s Board User’s Guide

The following table shows example noise results of the two different channels.

TABLE 2-1: MCP355X SENSOR APPLICATION DEVELOPER’S BOARD CHANNEL

PERFORMANCE EXAMPLE RESULTS (NOTE 1)

Channel

Effective Number of Bits

(ENOB)

“Noise-free” ENOB

“Noise-free

Resolution”

Channel 1 15.8 13.1 8,800:1 Channel 2 18.8 16.1 70,000:1

Direct Connection (No Gain) 13 10.4 1,350:1

Note 1: Higher resolution systems are possible with averaging and other design approaches, table only serves as

an example. Sensor used for these results was a 200 kg external load cell. Amplifier used in Channel 1 was MCP617 device. Amplifier used in Channel 2 was CS3002. All results using MCP3551 A/D Converter.

2.2 SENSOR INPUT CONNECTIONS

There are three connectors located on the right hand side of the board for external sensor input. The first is a standard DB9 connector that goes to a dual row 10-pin header. Jumper wires must be used to connect the output of the header to the 12-pin dual row headers going into either of the differential gain circuits described below.

In addition, there are two 3-terminal screw connectors, AUX1 and AUX2. These connectors go directly into the right hand side of the 40-pin dual row connector P8.

Note: Connector P6 is the input for channel 1, and P7 is the input for channel 2.

Depending on which sensor inputs (AUX1, AUX2, or the DB9 connector) are used to connect the external sensor to either channel, jumper wires must be connected to bring the input into either P6 or P7.

-SENSE

-IN

-OUT +OUT +IN

TO CHANNEL 1

TO CHANNEL 2

Analog Input Headers To Signal

Conditioning Circuits

+SENSE

-SENSE

-IN

-OUT +OUT +IN +SENSE

JUMPER WIRES (NOT INCLUDED)

FIGURE 2-2: Sensor Input Connections.

5 9 4 8 3 7 2

P10

Headers Supplied For External

Sensor Connection

6 1

Hardware Description

2.2.1 6-Wire and 4-Wire Load Cell Connections

P6 and P7 can be used to easily connect either 4 or 6-wire external load cell sensors. Figure 2-3 describes how jumpers can be used to short the “In” and “Sense” inputs for 4-wire load cell connections.

FIGURE 2-3: 6-Wire and 4-Wire Load Cell connections on P6 and P7.

The MCP355X Sensor Application Developer’s Board comes with 2 “Bridge Simulator” Boards that can be used in place of external sensors during system development. These boards are plugged directly into P6 and P7, see Section 2.5 “Bridge Simulator

Boards” for more information.

2.3 CHANNEL 1 - LOW-COST DIFFERENTIAL GAIN CIRCUIT USING MCP6XX AMPLIFIER

Channel 1 contains a differential gain circuit using a dual amplifier PDIP socket populated with Microchip’s MCP617 amplifier with two analog switches for offset cancellation. The goal of the circuit is to allow for the use of an operational amplifier with higher offset drift (which will generally mean a lower cost amplifier). The MCP617 is populated and configured to provide a differential gain of 21.

The board comes populated with R chosen such that the voltage noise at the output of the amplifier will be approximately 10 µV using the MCP617 amplifier will not provide any additional improvement to the system. Application note AN1030 details the operation of this circuit and also includes data and test results using a variety of external sensors.

, substantially above the 2.5 µV RMS noise of the MCP3551. Higher gains

RMS

=100Ω and RF = 1.0 kΩ. The gain of 21 was

MCP355X Sensor Application Developer’s Board User’s Guide

Analog Switch

MCP6XX Socket U9

SPI

REF

MCP3551

IN-

IN+

Analog Switch

-SENSE

-IN

-OUT +OUT +IN +SENSE

Switch Control From PIC16F877

FIGURE 2-4: Channel 1 Differential Gain Circuit with analog switch offset cancellation.

2.3.1 Channel 1 Analog Switches and Offset Drift Cancellation

The analog switches are used with the amplifier to swap the sources driving the load cell, effectively cancelling any offset or offset drift. One conversion is performed with the load cell driven “normally” and a second while it is driven in an “inverted” configuration. The result of the second conversion is inverted and added to the result from the first and an average of the two is computed (computing the average is a simple shift operation for the microcontroller). This technique effectively cancels the offset of the amplifiers as well as the ADC. An offset residue will exist if the any of the offsets change between conversions. This is unlikely to happen unless the temperature changes rapidly after the first conversion. The offset of the sensor is not affected by this technique.

The firmware included with this developer’s board performs this process when “Channel 1” is selected using the push button switches.

This process is described here:

1. Stop the output drive by configuring the outputs of the PICmicro MCU that drive the load cell as low.

2. Control the analog switches and switch the ground of the MCP3551 to the “bottom” of the load cell and the reference of the MCP3551 to the “top” of the load cell.

3. Start the output drive by configuring the output of the PICmicro MCU that drives the “top” of the load cell as high.

4. Perform a conversion and save the result.

5. Stop the output drive by configuring both outputs of the PICmicro MCU that drive the load cell as low.

6. Control the analog switches and switch the ground of the MCP3551 to the “top” of the load cell and the reference of the MCP3551 to the “bottom” of the load cell.

7. Start the output drive by configuring the output of the PICmicro MCU that drives the “bottom” of the load cell as high.

8. Perform a conversion, invert the result, add to the first conversion, divide by two, and save the result as the actual reading.

Hardware Description

2.4 CHANNEL 2 - HIGH-PRECISION GAIN CIRCUIT

Channel 2 contains a differential gain circuit using a low noise amplifier from Cirrus Logic, CS3002. The noise allows a differential amplifier gain of 103 V/V.

EQUATION 2-1:

G12

This was chosen so that the amplifier noise would be similar to that of the MCP3551 device, maximizing the resolution of the circuit. The board comes populated with R

=100Ω and RF = 5.1 kΩ. Higher gains can be chosen, however in this case, the

gain was chosen to allow for headroom near the supply rails (+5V and ground) to handle a large variety of sensors. For more information regarding gain selection and circuit results, refer to application note AN1030, “Weigh Scale Applications for the

MCP3551”.

MCP3551

JP2

IN-

IN+

REF

GAINDIRECTDIRECT+ GAIN+ VREF RC7 VDD

〈〉+=

------R

CS3002

-SENSE

-IN

-OUT +OUT +IN +SENSE

FIGURE 2-5: High Gain Circuit Using CS3002.

2.4.1 Channel 2 - Voltage Reference Selection

There are three options to select voltage reference for the MCP355X device for channel 2. This is accomplished using the 14-pin dual row header JP2. There are three options for voltage reference evaluation on the bottom of this header.

•V

REF

• PICmicro port pin RC6-7

•V

The first selection uses the stand-alone voltage reference circuit included on the board, populated with the low noise reference LM4140 from National Semiconductor Corporation.The second selection allows for evaluation of using the PICmicro port pins to supply the voltage reference for the circuit. The board uses two pins of the PICmicro microcontroller for increased drive, RC6 and RC7 of the PIC16F877. The third selection, V

, will supply the V

directly from the output of JP1, which selects the

REF

power supply for the board.

MCP355X Sensor Application Developer’s Board User’s Guide

2.4.2 Channel 2 - Direct-Connect Applications (No Amplifier or Gain)

Channel 2 can also be used to evaluate the MCP355X in a direct-connect sensor configuration. This is accomplished using the 14-pin dual row header JP2. Changing the headers to DIRECT+ and DIRECT- will take the signal present on the channel input header (P7) directly into the MCP355X. Figure 2-6 represents this circuit configuration using channel 2.

VIN-

FIGURE 2-6: A Direct-connect Weigh Scale.

VDDV

MCP3551

REF

2.5 BRIDGE SIMULATOR BOARDS

There are two small boards included with the MCP355X Sensor Application Developer’s Board. These boards represent a simulation of an external wheatstone bridge that is either at zero-scale or full-scale. These boards come populated with resistors that have a temperature drift specification of 10 ppm/C. For the best bridge simulation, it is recommended that the bridges be populated with very low drift resistors with a tempco value of 0.1 ppm/C. Typical load cell bridges will exhibit this output temperature drift. These boards can be plugged in to either P6 or P7 to assist in eliminating any error associated with an external sensor. Figure 2-7 represents the bridge simulator boards and how they should be connected to the MCP355X Sensor Application Developer’s Board. Refer to Appendix A. “Schematic and Layouts” for complete schematic.

P6 (OR P7)

-SENSE

-IN

-OUT +OUT +IN +SENSE

Bridge Simulator Boards

FIGURE 2-7: Bridge Simulator Boards.

DEVELOPER’S BOARD USER’S GUIDE

Chapter 3. Firmware Description

3.1 FIRMWARE OVERVIEW

The MCP355X Sensor Application Developer’s Board contains two PICmicro MCUs, the PIC18F4550, which is solely used to send ADC data to DataView on the PC and the PIC16F877 which interfaces to the LCD display. Both controllers come programmed with dedicated firmware that is described in this chapter.

3.2 PIC16F877

This device comes programmed with LCD firmware to ease weigh scale or other system design. The three push buttons F1, F2, and F3 control both the MCP3551 sampling and LCD output through the PIC16F877.

3.2.1 LCD Numerical Output Display

This display will change depending on the units selected and the values that are loaded into the zero calibrate, full-scale calibrate, and full-scale value registers. To show raw ADC output, the unit menu is used to select A/D units. When grams (g), or kilograms (kg) is selected, Equation 3-1 represents the algorithm and formula applied to yield an output on the LCD display.

MCP355X SENSOR APPLICATION

EQUATION 3-1:

ADC

⎛⎞

Output

Where:

ADC

VAL

ZERO

CAL

DI SPLAY_FS_VAL = 1, 2, 5, 10, 20, 50, 100, 200, or 500 (value selected

Note: The ZERO

disabled. See Section 3.2.2.1 “Zero calibrate” for complete description

----------------------------------------------------

⎝⎠

= The most recent value from the ADC after averaging. = The most recent ADC

is pressed.

= The most recent (ADC

calibrate full-scale switch is pressed.

using push button switches.) See Section 3.2.2.5 “Full-Scale Value Selection”

subtraction to remove zero offset can be enabled or

CAL

VAL

ZERO

–

CAL

DISPLAY_FS_VAL

when the calibrate zero switch

VAL

- ZERO

) when the

CAL

MCP355X Sensor Application Developer’s Board User’s Guide

3.2.2 Controlling the LCD Menu

The right most button F3 is the menu control button.

FIGURE 3-1: LCD showing the Averaging Menu. Also shown are the F1, F2 and F3 buttons.

Pressing this button will cycle through the menu options and change the functionality of the other two buttons, F1 and F2. The LCD text above the buttons describes the functionality for the different menus.

Here are the LCD menus that can be selected using the F3 button:

• Zero Calibrate - Enable/Disable/Hold

• Channel Select

•Units

• Averaging

• Full-Scale Value Selection

• Full-Scale Calibration

There are four different menu options that will be described in individual sections.

3.2.2.1 ZERO CALIBRATE

When in this menu, the first button becomes the ZERO button. When this button is selected, the most recent ADC value after averaging will be loaded into the ZERO register.

Zero calibration is also enabled or disabled by pressing the ZERO button. This is indicated by a change of the spinning character on the far top-right of the display, (i.e.: a LINE is inserted under the spinning character when zero calibration is turned ON.) When enabled, ZERO

is subtracted as per Equation 3-1. Refer to Figure 3-2.

CAL

FIGURE 3-2: These two icons show the presence of the zero offset substraction in the calculation. The icon on the right has a bar underneath that represents when zero subtraction is enabled.

Firmware Description

In disabled mode, ZERO direct ADC value (units = ADU), the output is simply the decimal representation of ADC displayed.

Pressing the HOLD button freezes the LCD display to allow for viewing in fast sampling modes (less averaging). Pressing the HOLD button again will resume normal operation.

3.2.2.2 CHANNEL SELECT

In this menu, the user has control over which channel is being sampled. There are four options. Pressing either F1 or F2 cycles through these options:

. If zero calibrate is enabled, then ZERO

VAL

is not subtracted per Equation 3-1. When displaying the

CAL

is subtracted before the value is

CAL

Channel 1 Normal

In this mode, the PIC16F877 samples the MCP3551 on channel 1. The LCD text above F2 will display “1N”. In the normal mode, the analog switches on this channel are set to the “positive” polarity. Refer to Chapter 2. “Hardware Description” for more description on the analog switch sampling.

Channel 1 Inverted

In this mode, the analog switches set to reverse polarity, and the inverted ADC sample is displayed on the LCD display. The LCD text above F2 will display “1I”. Refer to Chapter 2. “Hardware Description” for more description on the analog switch sampling.

Channel 1 Switched

In this mode, the PIC16F877 is switching back and forth between positive and reverse polarity and the averaged value is displayed on the LCD display. The LCD text above F2 will display “1S”. Refer to Chapter 2. “Hardware Description” for more description on the analog switch sampling.

Channel 2

In this mode, the PIC16F877 is sampling channel 2. This channel is the high gain circuit using amplifier CS3002. The resulting code is displayed on the LCD display.

3.2.2.3 UNITS

There are three units: A/D Units (ADU), grams (g), or kilograms (kg). When in this menu, pressing either F1 or F2 will change the text to the right of the numerical output to the proper unit and also display the appropriate representation of the A/D sample.

3.2.2.4 AVERAGING

In the averaging menu, the user can select how many samples are collected before the value is applied to the LCD output. This averaging applies all sampling situations, i.e. when calibrating zero, full scale, or displaying the output after calibration. The user can select between 1 (no averaging), 2, 4, 8, or 16 averages. The output noise of the system will be reduced by the square root of the number of averages per the equation below.

EQUATION 3-2:

MCP3551 Output Noise

Where:

N = the number of conversions

2.5 µV RMS

-----------------------------= N

MCP355X Sensor Application Developer’s Board User’s Guide

Note: If the channel mode “Channel 1 Switching” is selected, the averaging will

actually be twice due to the positive and reverse polarity switched samples being collected.

3.2.2.5 FULL-SCALE VALUE SELECTION

This menu options loads the DISPLAY_FS_VAL register. This is to allow for proper LCD display during system design. For example, if a system is being designed that uses “100 grams” as the full-scale calibration weight, this menu is used to set the value “100” into the DISPLAY_FS_VAL register. The full-scale value options are 1, 2, 5, 10, 20, 50, 100, 200, or 500.

Note: When displaying the value on the LCD display, the decimal point does not

move. This is to relax the LCD activity and keep the decimal point (and all digits) from constantly switching location when the LCD output is calculated.

3.2.2.6 FULL-SCALE CALIBRATION

When in this menu, the second button becomes the calibrate full-scale button, labeled OK. When this button is selected, the most recent ADC value, after averaging, will be loaded into the FS

CAL

3.3 PIC18F4550

This device acts as I2C slave and passes the PIC16F877 output data from either channel 1 or channel 2 to the DataView on the PC. All averaging and channel 1 switching that is performed by the PIC16F877 occurs before the data is passed to the PIC18F4550 and PC.

Note: The PIC18F4550 passes data to DataView on the PC coming from the

PIC16F877. This allows a system developer to write PIC16F877 firmware that averages or otherwise post processes ADC data and then use the PC to view this post processed data, see section below. Refer to Figure 2-1 for Data Flow.

4.1 OVERVIEW

DataView is a graphical data analysis tool that interfaces to many of Microchip’s stand-alone A/D converter demonstration or evaluation boards via USB interface. Each installation of Dataview is specific to the A/D converter and will contain one or more of the following graphical output windows:

• Scope Plot

• Histogram

• Auxiliary Data

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Chapter 4. DataView

Note: IMPORTANT! For the MCP355X Sensor Application Developer’s Board,

the USB microcontroller (PIC18F4550) is collecting post-processed data from the PIC16F877. By pressing the push button switches on the reference design and changing the processing that occurs on the PIC16F877, the data shown on DataView is also changed.

4.2 SCOPE PLOT WINDOW

The scope plot window graphs the A/D output as a function of sample or time. Each consecutive sample is added to the right of the data set and when the sample size is full, the scope plot will scroll to the left. The y-axis is displayed as the ADC code and the x-axis is given as sample number. The sample size can be changed in the configuration window.

FIGURE 4-1: Scope Plot Window.

MCP355X Sensor Application Developer’s Board User’s Guide

4.3 NOISE HISTOGRAM WINDOW

The noise histogram window displays the ADC output in histogram form, building the number of occurrences in each bin with each consecutive sample. The difference between each bin from the mean in units of LSB is given as the y-axis. The sample size can be changed in the configuration window.

FIGURE 4-2: Noise Histogram Window.

4.4 AUXILIARY DATA WINDOW

The auxiliary data window shows calculated data based on the current sample size. The mean of the sample set is given in both LSB and PPM. The standard deviation or RMS output noise is given in units PPM. The overflow bits of the MCP3551 are also monitored and the overflow bits are also given for both overflow high and overflow low situations.

FIGURE 4-3: Noise Histogram Window.

4.5 CONFIGURING DATAVIEW

The sample size and polling interval of the USB interface can be changed to accommodate customized firmware on the PICmicro microcontroller side. The units of millisecond, seconds, minute, hour or day can be used to change the functionality of the system. This allows the device to be used as a “Data Logger”. Note that if the polling interval is shorter than the sampling rate on the hardware size, duplicate data will be included in the sample set.

DataView

FIGURE 4-4: Configuration Window.

MCP355X Sensor Application Developer’s Board User’s Guide

NOTES:

Appendix A. Schematic and Layouts

A.1 INTRODUCTION

This appendix contains the following schematics and layouts for the MCP355X Sensor Application Developer’s Board:

• Board Schematic, Pages 1 thru 3

• Board Schematic - Bridge Simulator

• Board - Top Layer and Silk Screen

• Board - Top Layer

• Board - Bottom Layer and Silk Screen

• Board - Bottom Layer

• Board - Bridge Simulator Layout

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

MCP355X Sensor Application Developer’s Board User’s Guide

A.2 SCHEMATIC - PAGE 1

A.3 SCHEMATIC - PAGE 2

Schematic and Layouts

MCP355X Sensor Application Developer’s Board User’s Guide

A.4 SCHEMATIC - PAGE 3

A.5 SCHEMATIC - BRIDGE SIMULATOR

Schematic and Layouts

MCP355X Sensor Application Developer’s Board User’s Guide

A.6 BOARD LAYOUT - TOP LAYER AND SILK SCREEN

MCP355x SENSOR APPLICATION DEVELOPER'S BOARD

A.7 BOARD LAYOUT - TOP LAYER

Schematic and Layouts

A.8 BOARD LAYOUT - BOTTOM LAYER AND SILK SCREEN

A.9 BOARD LAYOUT - BOTTOM LAYER

MCP355X Sensor Application Developer’s Board User’s Guide

A.10 BOARD LAYOUT - BRIDGE SIMULATOR

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Appendix B. Bill Of Materials (BOM)

TABLE B-1: BILL OF MATERIALS (BOM)

Qty

17 C1, C3, C4, C5,

11 C2, C9, C10,

4 C7, C8, C13,

8 C23, C24 C25,

1 C38 CAP TANTALUM 2.2UF 16V 10%

4 C42, C43, C44,

2 D1, D2 DIODE SCHOTTKY 20V 0.5A

1 D3 LED SMD Standard SOT-23 HI

4 EA Corner BUMPON HEMISPHERE .44X.20

1 J1 9V Battery PCB Mount Vert

1 J2 Power Jack ,08" RA PCB Switchcraft RAPC722X

1 J3 CONN USB RECEPT R/A TYPE B

1 J4 9 Pin Right Angle Female

1 JP1 CONN HEADER RT/A .100 6POS

1 JP2 CONN HDR 14PIN GOLD VERT

1 L1 Shielded 10uH Power Inductor

1 M1 16 X 2 LCD Character Display Fema CG1626-SGR1

1 P1 Conn header pins used W/TERM

1 P1 CONN TERM BLK PLUG 6A

Designator Description Manufacturer Part Number

C6, C11, C12, C14, C15, C16, C17, C18, C29, C33, C34, C37, C39

C19, C20, C21, C22, C27, C30, C35, C36

C28

C26, C31 C32, C40, C41

C45

CAP .1UF 25V CERAMIC X7R 0805

CAP CER 10UF 6.3V X7R 0805 Murata Electronics

CAP CERAMIC 18PF 50V NP0 0805

DO NOT INSTALL — —

SMD 3216

CAP 470PF 50V CERM CHIP 0805 SMD

SOD123

EFF RED WTR CLR

BLACK

Connector Snap-on

4POS

Connector D-Sub

15AU

PCB

0805

BLK PLUG

3.5MM 2POS

Panasonic® - ECG ECJ-2VB1E104K

GRM21BR70J106KE76L

North America

Yageo® America CC0805JRNPO9BN180

EPCOS Inc B45196H3225K109

Panasonic - ECG ECJ-2VC1H471J

ON Semiconductor

Kingbright AM23EC-F

3M/ESM SJ-5003 (BLACK)

Keystone Electronics

AMP Electronics

Amphenol Canada 205A-09FGTBBC3

AMP/Tyco Electronics

CW Industries CWN-350-14-0000

Coilcraft 0805PS-103KLB

Keystone Electronics 8724

Keystone Electronics 8722

/Tyco®

MBR0520LT1G

968

292304-1

87230-3

MCP355X Sensor Application Developer’s Board User’s Guide

TABLE B-1: BILL OF MATERIALS (BOM) (CONTINUED)

Qty

2 P2, P4 6 X 1 Header 2.54mm on center 6

1 P3 5 X 2 Header 2.54mm on center 6

2 P5, P8 20 X 2 Header 2.54mm on center 6

2 P6, P7 6 X 2 Header 2.54mm on center 6

2 P9, P10 3.5mm Plugable 3-Position Screw

2 P9, P10 Conn header pins used W/TERM

1 PCB RoHS-compliant Bare PCB — 104-00090

10 R1, R5, R6,

2 R2, R3 RES 24.9 OHM 1/8W 1% 0805

3 R4, R30, R31 RES 332 OHM 1/8W 1% 0805 SMD Panasonic - ECG ERJ-6ENF3320V

4 R7, R8, R9,

1 R14 RES 887 OHM 1/8W 1% 0805 SMD Panasonic - ECG ERJ-6ENF8870V

11 R16, R17, R18,

6 R19, R21, R27,

4 R32, R33, R34,

2 R36, R37 1K Ohm 0.1% 0805 10ppm Thin

2 R38, R43 100 Ohm 0.1% 0805 10ppm Thin

2 R40, R41 5.1K Ohm 0.1% 0805 10ppm Thin

1 R44 DO NOT INSTALL — —

4 SW1 - SW4 SWITCH TACT 6MM SMD MOM

2 TP1, TP2 Wire Test Point 0.3" Length Nedco Electronics PJ-202-30

4 TP3, TP4 TP5,

1 U1 5.0V 3-Terminal 800mA Positive

1 U2 44-Pin, High-Performance,

1 U3 IC SOCKET STRAIGHT 40POS

Designator Description Manufacturer Part Number

Samtec TSW-106-07-G-S

mm/2.5mm

Samtec TSW-105-07-G-D

mm/2.5mm

Samtec TSW-120-07-G-D

mm/2.5mm

Samtec TSW-106-07-G-D

mm/2.5mm

Keystone Electronics 8723

Terminal Blocks

Keystone Electronics 8724

BLK PLUG

Yageo

America RC0805FR-074K7L

Panasonic - ECG ERJ-6ENF24R9V

Panasonic - ECG ERJ-3EKF10R0V

Susumu RG2012N-102-B-T1

Susumu RG2012N-101-B-T1

Susumu RG2012N-512-B-T1

Omron Electronics Inc

National Semiconductor

Microchip Technology Inc.

Assmann Electronics Inc

B3S-1002

LM1117-5.0

PIC18F4550-I/PT

A40-LC-TT-R

R11, R13, R14, R15, R20, R22, R26

R10, R12

R23, R24, R25, R29, R45, R46, R47, R48

R28, R39, R42

R35

TP6

4.7K 1% 0805 Thick Film Chip Resistor

SMD

RES 475 OHM 1/8W 1% 0805 SMD Panasonic - ECG ERJ-6ENF4750V

RES 100 OHM 1/8W 1% 0805 SMD Panasonic - ECG ERJ-6ENF1000V

RES 10.0 OHM 1/10W 1% 0805 SMD

RES 0.0 OHM 1/8W 5% 0805 SMD Panasonic - ECG ERJ-6GEY0R00V

Film Chip Resistor

230GF

DO NOT INSTALL — —

Regulator SOT-223

Enhanced Flash, USB Microcontroller

.600 TIN

Bill Of Materials (BOM)

TABLE B-1: BILL OF MATERIALS (BOM) (CONTINUED)

Qty

1 U3 40-Pin Enhanced Flash Microcon-

1 U4 256K I2C™ CMOS Serial EEPROM Microchip

2 U5, U6 22-Bit Delta Sigma ADC SO-8 Microchip

2 U7, U8 IC SWITCH ANALOG SPDT LV

1 U9 Dual Op-Amp DIP-8

1 U9 IC SOCKET STRAIGHT 8POS TIN Assmann Electronics

1 U10 I2C Temperature Sensor SO-8 Microchip

1 U11 Dual Op-Amp SO-8 Cirrus Logic CS3002-ISZ

1 U12 4.096V Voltage Reference SO-8 National Semicon-

2 X1, X2 20.000MHZ Crystal 10PF 5mm X

Designator Description Manufacturer Part Number

trollers

SC70-6

(Install in socket))

3.2mm SMD

Microchip Technology Inc.

Technology Inc.

Fairchild Semiconductor

Microchip Technology Inc.

Inc

Technology Inc.

ductor

Abracon Corporation ABM3B-20.000MHZ-10-1-U-T

PIC16F877A-I/P

24FC256-I/SN

MCP3551-E/SN

FSA4157P6X_NL

MCP617-I/P

A08-LC-TT-R

MCP9803-M/SNG

LM4140ACM-4.1

WORLDWIDE SALES AND SERVICE

AMERICAS

Corporate Office

2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: http://support.microchip.com Web Address: www.microchip.com

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ASIA/PACIFIC

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Tel: 61-2-9868-6733 Fax: 61-2-9868-6755

China - Beijing

Tel: 86-10-8528-2100 Fax: 86-10-8528-2104

China - Chengdu

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China - Fuzhou

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China - Xian

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ASIA/PACIFIC

India - Bangalore

Tel: 91-80-4182-8400 Fax: 91-80-4182-8422

India - New Delhi

Tel: 91-11-5160-8631 Fax: 91-11-5160-8632

India - Pune

Tel: 91-20-2566-1512 Fax: 91-20-2566-1513

Japan - Yokohama

Tel: 81-45-471- 6166 Fax: 81-45-471-6122

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Tel: 82-54-473-4301 Fax: 82-54-473-4302

Korea - Seoul

Tel: 82-2-554-7200 Fax: 82-2-558-5932 or 82-2-558-5934

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Philippines - Manila

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Singapore

Tel: 65-6334-8870 Fax: 65-6334-8850

Taiwan - Hsin Chu

Tel: 886-3-572-9526 Fax: 886-3-572-6459

Taiwan - Kaohsiung

Tel: 886-7-536-4818 Fax: 886-7-536-4803

Taiwan - Taipei

Tel: 886-2-2500-6610 Fax: 886-2-2508-0102

Thailand - Bangkok

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EUROPE

Austria - Wels

Tel: 43-7242-2244-399 Fax: 43-7242-2244-393

Denmark - Copenhagen

Tel: 45-4450-2828 Fax: 45-4485-2829

France - Paris

Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79

Germany - Munich

Tel: 49-89-627-144-0 Fax: 49-89-627-144-44

Italy - Milan

Tel: 39-0331-742611 Fax: 39-0331-466781

Netherlands - Drunen

Tel: 31-416-690399 Fax: 31-416-690340

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UK - Wokingham

Tel: 44-118-921-5869 Fax: 44-118-921-5820

02/16/06

Microchip Technology MCP355X Sensor Application Developer’s Board User guide

Specifications and Main Features

Frequently Asked Questions

User Manual

Preface

INTRODUCTION

DOCUMENT LAYOUT

CONVENTIONS USED IN THIS GUIDE

RECOMMENDED READING

THE MICROCHIP WEB SITE

CUSTOMER SUPPORT

DOCUMENT REVISION HISTORY

Chapter 1. Product Overview

1.1 INTRODUCTION

1.2 WHAT IS THE MCP355X SENSOR APPLICATION DEVELOPER’S BOARD?

1.3 WHAT THE MCP355X SENSOR APPLICATION DEVELOPER’S BOARD KIT INCLUDES

2.1 OVERVIEW

Chapter 2. Hardware Description

2.2 SENSOR INPUT CONNECTIONS

2.3 CHANNEL 1 - LOW-COST DIFFERENTIAL GAIN CIRCUIT USING MCP6XX AMPLIFIER

2.4 CHANNEL 2 - HIGH-PRECISION GAIN CIRCUIT

2.5 BRIDGE SIMULATOR BOARDS

Chapter 3. Firmware Description

3.1 FIRMWARE OVERVIEW

3.2 PIC16F877

3.3 PIC18F4550

4.1 OVERVIEW

Chapter 4. DataView

4.2 SCOPE PLOT WINDOW

4.3 NOISE HISTOGRAM WINDOW

4.4 AUXILIARY DATA WINDOW

4.5 CONFIGURING DATAVIEW

Appendix A. Schematic and Layouts

A.1 INTRODUCTION

Appendix B. Bill Of Materials (BOM)

WORLDWIDE SALES AND SERVICE