Microchip Technology MCP3421 Weight Scale Demo Board User guide

MCP3421

Weight Scale Demo Board

User’s Guide

 2010 Microchip Technology Inc. DS51918A

Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specification contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.

• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

• Microchip is willing to work with the customer who is concerned about the integrity of their code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.

Information contained in this publication regarding device
applications and t he lik e is provided only for your convenience
and may be su perseded by upda t es . It is y our responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life supp ort and/or safety ap plications is entir ely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless M icrochip from any and all dama ges, claims,
suits, or expenses re sulting from such use. No licens es are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights.

Trademarks

The Microchip name and logo, the Microchip logo, dsPIC,
K

EELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,

32

PIC

logo, rfPIC and UNI/O are registered trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.

FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MXDEV, MXLAB, SEEVAL and The Embedded Control
Solutions Company are registered trademarks of Microchip
Technology Incorporated in the U.S.A.

Analog-for-the-Digital Age, Application Maestro, CodeGuard,
dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial
Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified
logo, MPLIB, MPLINK, mTouch, Octopus, Omniscient Code
Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,
PICtail, REAL ICE, rfLAB, Select Mode, Total Endurance,
TSHARC, UniWinDriver, WiperLock and ZENA are
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.

SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.

All other trademarks mentioned herein are property of their
respective companies.

© 2010, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.

Printed on recycled paper.

ISBN: 978-1-60932-687-6

Microchip received ISO/TS-16949:2002 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.

®

MCUs and dsPIC® DSCs, KEELOQ

®

code hopping

DS51918A-page 2  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Table of Contents

Preface ........................................................................................................................... 5

Chapter 1. Product Overview

1.1 Overview ............. ........................................................................................... 9

1.2 Analog Input Configuration Options ........................ .................... .................10

1.3 Load Cell ......................................................................................................11

1.4 Universal Serial Bus (USB) and PIC18F4550 Microcontroller .... .................12

1.5 What the MCP3421 Weight Scale Kit Contains ...........................................12

Chapter 2. Installation and Operation

2.1 MCP3421 Configuration Bit Settings and Data Acquisition ..........................13

2.2 USB Commu n ic a tio n ................................................................ .................... 13

Chapter 3. Weight Scale PC Software Tool

3.1 Software In stallation .............................................................................. ....... 15

3.2 Software Ove r view ....... .. ........................... .. .. ............................................... 15

3.3 Weight Scale Calibration ........................................ ...................................... 16

Appendix A. Schematics and Layouts

A.1 Introduction ..................................................................................................17

A.2 Board – Schematic ... .................................................................... ................ 18

A.3 Board – Top Copper and Pads ....................................................................19

A.4 Board – Top Pads and Silk ...................... .................... .. .................... .. ........20

A.5 Board – Top Copper, Pads and Silk ... ......................... .. ............................ ..21

A.6 Board – Bottom Copper and Pads ...............................................................22

Appendix B. Bill of Materials

Worldwide Sales and Service .................................................................................... 26

 2010 Microchip Technology Inc. DS51918A-page 3

MCP3421 Weight Scale Demo Board User’s Guide

NOTES:

DS51918A-page 4  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Preface

NOTICE TO CUSTOMERS

All documentation becomes dated, and this manual is no exception. Microchip tools and
documentation are constantly evolving to meet customer needs, so some actual dialogs
and/or tool descriptions may differ from those in this document. Please refer to our web site
(www.microchip.com) to obtain the latest documentation available.

Documents are identified with a “DS” number. This number is located on the bottom of each
page, in front of the page number. The numbering convention for the DS number is
“DSXXXXXA”, where “XXXXX” is the document number and “A” is the revision level of the
document.

For the most up-to-date information on development tools, see the MPLAB
Select the Help menu, and then Topics to open a list of available on-line help files.

®

IDE online help.

INTRODUCTION

This chapter contains general information that will be useful to know before using the
MCP3421 Weight Scale 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 MCP3421 Weight Scale 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” – Provides important information about the
MCP3421 Weight Scale Demo Board hardware.

• Chapter 2. “Installation and Operation” – Describes the MCP3421 Weight
Scale Demo Board firmware.

• Chapter 3. “Weight Scale PC Software Tool” – Provides detailed information
about the board’s PC software tool.

• Appendix A. “Schematics and Layouts” – Shows the schematic and board
layouts for the MCP3421 Weight Scale Demo Board.

• Appendix B. “Bill of Materials” – Lists the parts used to build the MCP3421
Weight Scale Demo Board.

 2010 Microchip Technology Inc. DS51918A-page 5

MCP3421 Weight Scale Demo Board User’s Guide

CONVENTIONS USED IN THIS GUIDE

This manual uses the following docum entat io n conven tion s:

DOCUMENTATION CONVENTIONS

Description Represents Examples

Arial font:

Italic chara c ters Referenced books MPLAB

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 brac kets < > 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 r epeated text var_name [,

A menu path File>Save

A tab Click the Power tab

where N is the tota l number of
digits, R is th e radi x 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 mut ually exclus ive
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)

{ ...
}

®

IDE User’s Guide

DS51918A-page 6  2010 Microchip Technology Inc.

RECOMMENDED READING

This user’s guide describes how to use MCP3421 Weight Scale Demo Board. Other
useful documents are listed below. The following Microchip documents are available
and recommended as supplemental reference resources:

• MCP3421 Data Sheet – 18-Bit Analog-to-Digital Converter with I
Interface and On-Board Reference (DS22003)

• MCP3422/3/4 Data Sheet – 18-Bit, Multi-Channel ΔΣ Analog-to-Digital
Converter with I

• MCP6V07 Data Sheet – 300 µA, Auto-Zeroed Op Amps (DS22093)

• PIC18F4550 Data Sheet – 28/40/44-Pin, High-Performance, Enhanced Flash,
USB Microcontrollers with nanoWatt Technology (DS39632)

• AN1030 – Weigh Scale Applications for the MCP3551 (DS01030)

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

2

C™ Interface and On-Board Reference (DS22088)

Preface

2

C™

CUSTOMER SUPPORT

Users of Microchip products can receive assistance through several channels:

• Distributor or Representative

• Local Sales Office

• Field Application Engineer (FAE)

• Technical Support

Customers should contact their distributor, representative or field application engineer
(FAE) for support. Local sales offices are also available to help customers. A listing of
sales offices and locations is included in the back of this document.

Technical support is available through the web site at: http://support.microchip.com.

DOCUMENT REVISION HISTORY

Revision A (November 2010)

• Initial Release of this Document.

 2010 Microchip Technology Inc. DS51918 A-page 7

MCP3421 Weight Scale Demo Board User’s Guide

NOTES:

DS51918A-page 8  2010 Microchip Technology Inc.