File Transfer Protocol Using MPLAB Harmony v3 TCP/IP Stack

AN3475

File Transfer Protocol Using MPLAB Harmony v3 TCP/IP

Stack

Introduction

File Transfer Protocol (FTP) is an application layer protocol used to transfer files between local and remote hosts. It

runs on top of the TCP, such as HTTP.

This document focuses on the FTP implementation of the MPLAB

Harmony v3 TCP/IP stack, available in the latest

MPLAB Harmony v3 framework. It also provides an FTP client demonstration using the SAM E70. This

demonstration implements an Ethernet bootloader using FTP, through which the SAM E70 client downloads a binary

for self-programming from an FTP server.

Abbreviations

The following abbreviations are used in this document:

• FTP – File Transfer Protocol

• HTTP - Hypertext Transfer Protocol

• TCP/IP – Transmission Control Protocol/Internet Protocol

• DHCP - Dynamic Host Configuration Protocol

• DFP - Device Family Pack

• MHC - MPLAB Harmony Configurator

Application Note

DS00003475A-page 1

Table of Contents

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

1. FTP Overview......................................................................................................................................... 3

1.1. Client............................................................................................................................................ 3

1.2. Server...........................................................................................................................................3

1.3. Connection................................................................................................................................... 3

1.4. Operation Modes..........................................................................................................................4

1.5. FTP Applications.......................................................................................................................... 4

2. FTP in MPLAB Harmony v3.................................................................................................................... 5

2.1. FTP Server Module...................................................................................................................... 5

2.2. FTP Client Module........................................................................................................................5

3. FTP Client: Bootloader Application......................................................................................................... 7

3.1. Prerequisites................................................................................................................................ 7

3.2. Application Overview....................................................................................................................7

3.3. Running the Application............................................................................................................. 12

4. Troubleshooting.....................................................................................................................................17

5. Appendix............................................................................................................................................... 18

5.1. Generating Application Binary Files........................................................................................... 18

5.2. Self-Programming of Downloaded Binary.................................................................................. 20

6. References............................................................................................................................................22

The Microchip Website.................................................................................................................................23

Product Change Notification Service............................................................................................................23

Customer Support........................................................................................................................................ 23

Microchip Devices Code Protection Feature................................................................................................ 23

Legal Notice................................................................................................................................................. 23

Trademarks.................................................................................................................................................. 24

Quality Management System....................................................................................................................... 24

Worldwide Sales and Service.......................................................................................................................25

AN3475

Application Note

DS00003475A-page 2

1. FTP Overview

FTP is built on a client/server model architecture using separate control and data connections between the client and

the server.

Figure 1-1. FTP Model

UserInterface

UserPI

UserDTP

FTPClient

ServerPI

ServerDTP

FTPServer

FileSystemFileSystem

User

ControlConnection

DataConnection

PI:ProtocolInterpreter

DTP:DataTransferProcess

1.1 Client

A File Transfer Protocol client (FTP client) is a software that establishes a connection between a host computer and a

remote FTP server. An FTP client provides the dual-direction transfer of data and files between two computers over

TCP. An FTP client works on a client/server architecture, where the host computer is the client and the remote FTP

server is the central server. It works when the host computer connects to the FTP server by specifying the domain, IP

address, user name, and password of that server (in some cases, the port number also needs to be specified). After

the user authentication, a connection is established between both the systems, and the host computer can upload

data onto the FTP server. An FTP client generally supports one or multiple simultaneous file transfers. Moreover,

most FTP clients can connect to multiple FTP servers simultaneously, providing status updates of the uploading

process, and notifications about successful and failed transfers. The host computer can also download files from the

FTP server using the FTP client.

1.2 Server

The FTP server enables downloading and uploading files. There could be access restrictions, which are determined

by the FTP server administrator for downloading the various files and folders residing on the FTP server. Files

residing on FTP servers can be retrieved by common web browsers, but they may not support protocol extensions,

such as FTPS (FTP Secure). All file transfer protocol site addresses begin with ‘ ftp://’.

1.3 Connection

To transfer a file, the following TCP connections are used by the FTP in parallel: control connection and data

connection.

Control Connection: FTP uses control connection for sending control information, such as user identification,

password, commands to change the remote directory, and commands to retrieve and store files. The default port

number for control connection is 21. All control connections are initiated on this port.

Data connection: For sending the file, FTP uses data connection. The default port number for data connection is 20.

However, data connections are not always initiated on this port. Depending on the mode of operation, they may be

initiated in other port numbers. For additional information, refer to 1.4 Operation Modes.

Session:

AN3475

FTP Overview

Application Note

DS00003475A-page 3

When an FTP session is started between a client and a server, the client initiates a control TCP connection with the

server side. The client sends control information over this. When the server receives control information, it initiates a

data connection to the client side. Only one file can be sent over one data connection. But the control connection

remains active throughout the user session.

1.4 Operation Modes

FTP can operate in the following two modes, which determines how a data connection is established. In both cases,

the control connection is established with an FTP server on port 21.

Active Mode: In Active mode, the server initiates the data channel connection. The sequence of connection is as

follows:

• The client connects from a random port to port 21 on the FTP server. This is the control/command channel.

• Using the control connection, the client informs (through PORT command) the port number on which it is

listening. This port will be used for the data channel.

• Server connects from port 20 to the client port designated for the data channel

Active mode is more secure for the server as it does not require unsecured ports to be open at the server end. It is

the server that initiates the data connection to the client. However, it must be noted that Active mode is less secure

for the clients.

Active mode may fail in cases where the client is behind a firewall as the firewall might block incoming server

connections (for the data channel), if the random port of the server is not unblocked in the firewall.

Passive Mode: In passive mode, the client initiates the data channel connection.

• The client connects from a random port to port 21 on the FTP server. This is the control/command channel.

• Client issues the PASV command

• Server replies with a random port number for the data channel

• Client connects from a random port to the port number specified by the server

Passive mode is recommended for clients protected by a firewall, because no inbound connection requests to the

client.

Modes based on Data Representation

FTP allows files to be transferred in several formats:

• ASCII mode: This mode is used for plain text files or ASCI-based files, such as an HTML file, text file, or

PostScript. ASCII is the default transfer type.

• Binary mode: This mode is also known as Image mode, and it is used for transferring non-ASCII files, such as

images, applications, and generated archive/cabinet files, such as .zip and .tar files. In this mode, the file is

transferred without any conversion. This maintains an identical file structure on both machines. This is important

for files such as pictures, music, and videos which must be exact copies to preserve integrity of the data.

• EBCDIC mode: This mode is used for plain text between hosts using the EBCDIC character set.

1.5 FTP Applications

FTP has a wide range of applications, which span from day-to-day business operations to data transfer from

embedded systems. The following examples show some use cases:

• Organizations use FTP to allow employees to share files across different locations and branch offices.

• Employees use FTP to share files with coworkers and external business partners.

• IT teams use FTP to transfer data back to disaster recovery (DR) sites.

• Webmaster teams use FTP to transfer web pages, web application files, and images to their web server..

• Remote embedded systems use FTP to download application binary for firmware updates

• Retrieve log files stored in remotely operated MCUs and MPUs.

AN3475

FTP Overview

Application Note

DS00003475A-page 4

2. FTP in MPLAB Harmony v3

The TCP/IP stack library of MPLAB Harmony v3 provides the API of the FTP module with a convenient ‘C’ language

interface. It supports the FTP server and client, which facilitating the upload and download of files to an embedded

client and server.

2.1 FTP Server Module

The interface to the FTP TCP/IP stack library is defined in the ftp.h header file. To use the FTP server in a project

requires using the TCP/IP stack and a file system like FAT FS.

The FTP server can be enabled in the MPLAB Harmony v3 TCP/IP project using MHC: Project Graph > Application

Layer > TCP/IP Application Layer Configurator > FTP Server.

Figure 2-1. Project Graph

Table 2-1. FTP Server Module Files

File Description

ftp_config.h Configuration of the FTP server (from symbols generated in configuration.h)

ftp.h Interface to the FTP server TCP/IP Stack library

ftp.c Implementation of FTP server

Additional information on the FTP server module are found at https://github.com/Microchip-MPLAB-Harmony/net/

blob/master/doc/help_harmony_tcpip.pdf.

2.2 FTP Client Module

The FTP client module enables transfer of data reliably and efficiently between different devices, without worrying

about the different file storage systems among hosts.

Table 2-2. FTP Client Module Files

File Description

ftpc_config.h Configuration of the FTP Client (from symbols generated in configuration.h)

ftpc.h Interface to the FTP client TCP/IP stack library

ftpc.c Implementation of FTP client protocol

The following table displays some of the FTP commands supported by the FTPC module.

AN3475

FTP in MPLAB Harmony v3

Application Note

DS00003475A-page 5

Table 2-3. FTP Commands Supported by the FTPC Module

FTP COMMAND STACK COMMAND TYPE FUNCTION NAME

USER - send username TCPIP_FTPC_CMD_USER TCPIP_FTPC_Login

PASS - send password TCPIP_FTPC_CMD_PASS TCPIP_FTPC_Login

ACCT - send account information TCPIP_FTPC_CMD_ACCT TCPIP_FTPC_Login

TYPE - set transfer type TCPIP_FTPC_CMD_TYPE TCPIP_FTPC_SetType

STRU - set file transfer structure TCPIP_FTPC_CMD_STRU TCPIP_FTPC_SetStruct

MODE - set transfer mode TCPIP_FTPC_CMD_MODE TCPIP_FTPC_SetMode

PASV - enter passive mode TCPIP_FTPC_CMD_PASV TCPIP_FTPC_SetActiveMode

TCPIP_FTPC_SetPassiveMode

PORT - open a data port TCPIP_FTPC_CMD_PORT TCPIP_FTPC_Connect

RETR - retrieve a remote file TCPIP_FTPC_CMD_GET TCPIP_FTPC_GetFile

STOR - store a file on the remote host TCPIP_FTPC_CMD_PUT TCPIP_FTPC_PutFile

NLST - name list of remote directory TCPIP_FTPC_CMD_NLST TCPIP_FTPC_NameList

LIST - list remote files TCPIP_FTPC_CMD_LIST TCPIP_FTPC_List

DELE - delete a remote file TCPIP_FTPC_CMD_DELE TCPIP_FTPC_DeleteFile

CWD - change working directory TCPIP_FTPC_CMD_CWD TCPIP_FTPC_Change_Dir

CDUP - CWD to the parent of the current

directory

TCPIP_FTPC_CMD_CDUP TCPIP_FTPC_ChangeToParentDir

MKD - make a remote directory TCPIP_FTPC_CMD_MKD TCPIP_FTPC_MakeDir

RMD - remove a remote directory TCPIP_FTPC_CMD_RMD TCPIP_FTPC_RemoveDir

PWD - print working directory TCPIP_FTPC_CMD_PWD TCPIP_FTPC_Get_WorkingDir

QUIT - terminate the connection N/A TCPIP_FTPC_Logout

In addition to the implementation of FTP commands, the client module provides a user interface through the USART

terminal. This enables users to provide the required FTP command by entering into the terminal.

All FTP client commands start with the keyword ‘ftpc’, for example, ftpc login <username> <pswd> .

AN3475

FTP in MPLAB Harmony v3

Application Note

DS00003475A-page 6

3. FTP Client: Bootloader Application

The following sections cover software and hardware required for this application, and it also covers overview of the

application.

3.1 Prerequisites

Hardware:

• SAM E70 Xplained Ultra evaluation kit – 1 No.

• SD card – 1 No.

• Ethernet cable (RJ45) – 1 No.

• USB cable – 1 No.

Software:

• MPLAB X IDE (v5.30)

• MPLAB XC32/32++ Compiler (v2.40)

• MPLAB Harmony Configurator (v3.4.0)

– Harmony bsp repository, v3.5.0

– Harmony csp repository, v3.5.2

– Harmony core repository, v3.5.2

– Harmony dev_packs repository, 3.5.0

– Harmony net repository v3.5.1

3.2 Application Overview

This example demonstrates creating an application where an FTP client downloads a binary file from the FTP server,

which in turn used to Flash the microcontroller. The FAT-FS File System with SDCARD as storage media is used in

this application and the FTP client will write to and read from this FS.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 7

Figure 3-1. Flow Diagram

3.2.1 Application Code

The user application for an FTP client must initiate the FTP connection request. Based on the server’s response for

the request, the username and password must be provided by the client for logging in. When the FTP client is

successfully logged in, data can be transferred between the server and the client. In this application, the client

downloads a binary file from the server and the downloaded file will be stored on an SD card. The binary is then

flashed to the microcontroller.

The following code displays the application code for the FTP connection and login.

case APP_Connect_FTP:

TCPIP_FTPC_Get_Status (ftpcHandle, &ftpcStatus);

if (ftpcStatus.isConnected)

{

SYS_CONSOLE_MESSAGE ("FTP Client connected \r\n");

appData.state = APP_Logign_FTP;

SYS_CONSOLE_MESSAGE ("Login with your credentials \r\nEg: ftpc login

username psswd\r\n");

}

break;

case APP_Login_FTP:

TCPIP_FTPC_Get_Status (ftpcHandle, &ftpcStatus);

if (ftpcStatus.isLoggedIn)

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 8

{

SYS_CONSOLE_MESSAGE ("FTP Client logged in \r\n");

appData.state = APP_SET_CURRENT_DRIVE;

}

break;

3.2.2 Creating the Application

This application is created in MPLAB Harmony configurator as it provides an easy-to-use GUI that simplifies device

setup, library selection, configuration and application development.

For additional information on the MHC, refer to https://github.com/Microchip-MPLAB-Harmony/mhc/wiki .

MPLAB Harmony Configuration

• To create a 32-bit MPLAB Harmony v3 project for the SAME70Q21B using MPLAB X IDE, refer to https://

microchipdeveloper.com/harmony3:same70-getting-started-training-module)

• By default, the Device Family Pack (DFP), System, CMSIS Pack and EFC will be present when the

configuration is launched.

• For this demonstration, the Terminal communication, System service, File System, and TCP/IP features must be

added.

• The harmony configuration file (.xml) with these components configured can be found in the source code of this

application note (ftp_bootloader\firmware\src\config\default\sam_e70_xult.xml).

Load this file from the MPLAB Harmony configurator: MPLAB Harmony Configurator > File > Load State.

• The following figure illustrates the complete project graph:

Figure 3-2. Complete Project Graph

• Because this document focuses on FTP, the TCP/IP related configurations are highlighted below:

TCP/IP Harmony configuration

– For TCP/IP Basic Configurator, follow these steps:

1. Adding the TCP/IP Basic Configurator will create a BASIC CONFIGURATION view. Different views

can be selected as shown in the following figure.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 9

Figure 3-3. Selecting Views

2. In the Basic Configurator view, TCPIP CMD, TCPIP CORE and NETCONFIG components are

enabled.

Figure 3-4. Basic Configurator View

3. In the TCP/IP CORE configuration options, the TCP/IP Stack Dynamic RAM Size can be adjusted

per the application requirement. For this example the RAM allocated is 67,960 bytes (66 KB).

Figure 3-5. Configuration Options

4. In NETCONFIG options, the necessary network details, such as IP address and gateway address

are configured:

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 10

Figure 3-6. NETCONFIG Options

– TCP/IP Application Layer Configurator

1. In the APPLICATION LAYER view, the TCP/IP Application Layer Configurator is used to enable

ANNOUNCE, FTP CLIENT and DHCP CLIENT components. The ANNOUNCE module facilitates

device discovery on the DHCP-enabled networks, while the DHCP CLIENT module allows the

application to dynamically obtain an IP address from a DHCP server on the network.

Figure 3-7. APPLICATION LAYER View

2. In the FTP CLIENT configuration, the Enable FTP Client Commands option allows users to interact

with the FTP client through a serial terminal. Transmit and receive buffer size can be increased as

required (that is, 1,024).

Figure 3-8. FTP CLIENT Configuration

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 11

3.3 Running the Application

3.3.1 Hardware Setup

Follow these steps to setup the hardware:

1. Ensure that the ERASE jumper is open.

2. Open the J805 Jumper..

3. Insert the LAN8740 PHY daughter board on the ETHERNET PHY MODULE header.

4. Connect the micro-USB cable from the computer to the DEBUG USB connector on the SAM E70 Xplained

Ultra Evaluation Kit.

5. Establish a connection between the router/switch with the SAM E70 Xplained Ultra Evaluation Kit through the

RJ45 connector. An IP address will be assigned to the kit by the DHCP server on the network. The kit can also

be connected to the RJ45 port on the PC, hence a DHCP server may be unavailable and a pre-configured

static IP address will be used by the kit.

6. Insert the SD card to the SD card slot on the backside of the hardware board.

3.3.2 Programming the MCU

Follow these steps to program the MCU:

1. Open the project in MPLAB X IDE: (File > Open Project, and then browse to ftp_bootloader\firmware

\sam_e70_xult.X).

2. Build and program the project to the target board by clicking (Make and Program device icon).

3.3.3 Setting up FTP Server

Before running the FTP client application, users need to follow these steps to setup the FTP server.

For this demonstration, the FileZilla Server Interface is used as the FTP server running on the user PC. Refer to

https://wiki.filezilla-project.org/Documentation for additional information.

Follow these steps to setup FileZilla server::

1. Open the FileZilla server interface.

2. In the pop-up window, enter a hostname, port, and password for the admin interface.

3. Click Connect.

4. Click

(user icon), or go to Edit > User for adding the client.

5. In the User window, click General. Add the client by clicking Add , and then enable the account and password.

This will be the user name and password for connecting from the FTP client.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 12

Figure 3-9. User Window

6. In the Shared folders section, add the path of the folder where the binary to be downloaded is located.

Figure 3-10. Adding the Path

3.3.4 Connecting FTP Client

Follow these steps to connect the FTP client:

1. From a terminal window application (lTera Term), connect to the COM port enumerated by the SAM E70

Xplained Ultra board.

2. Restart the application (that is, reset the SAM E70 board).

3. The IP address will be displayed on the terminal after it is ready, the user can connect to the FTP server by

typing: ftpc connect <host ip address>.

4. Upon successful connection, enter the login details: ftpc login <username> <password>.

5. Once logged in, use the following ftpc to get the command to download a binary from the server: ftpc get -

a -a <test.bin>.

Note: Refer to the section Appendix for steps to generate a binary file.

6. After the binary is successfully downloaded, it can be flashed to the MCU by using the boot command.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 13

Note: This project is configured for a maximum binary file size of 7 KB. For binary files larger than this,

increase APP_DATA_LEN macro in app.c file of the ftp_bootloader project. If the binary file is larger than

available RAM, the file can be read in chunks (instead of reading complete file into buffer) and programmed.

7. The MCU is reset automatically after the programming is complete, and the application code starts executing.

Displaying the message: **** Executing Application code ****.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 14

Figure 3-11. Output:

After the MCU reset, the following message is displayed, indicating that the MCU has been reprogrammed

with a new application binary.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 15

Figure 3-12.

AN3475

FTP Client: Bootloader Application

Application Note

DS00003475A-page 16

4. Troubleshooting

This section covers important error messages and appropriate workaround for that.

• “FTP timed out” - Server response time can be affected by the distance between the sites. If you see this

message when connecting to a server, increase the Connect Timeout setting to give the server more time to

respond during the login process.

• “Cannot open data connection” - If this error is encountered in a Windows system with the Firewall enabled, it

may be due to the firewall blocking the connection on the corresponding FTP data port. Try disabling the firewall

temporarily and see if the FTP connection succeeds. If the connection is successful with the firewall disabled,

users can configure the firewall to allow the required port and enable it.

• Client unable to connect using PASV (passive) mode - Ensure that the server is configured to accept passive

connection. For example, in the FileZilla server the passive mode can be enabled by disabling Active mode:

FileZilla Server > Server > Active.

AN3475

Troubleshooting

Application Note

DS00003475A-page 17

5. Appendix

5.1 Generating Application Binary Files

In general, for implementation where the bootloader is available in Flash, bootloaders are present at the base

(starting) address of the Flash memory. The application is loaded to the memory in Flash, which is beyond the

bootloader.

Flash

Bootloader

Application

0x0000

To generate the binary file of an application project in MPLAB X IDE, perform these actions:

1. Modify Application Start Address.

2. Execute the post build command to generate the bin file.

5.1.1 Modifying Application Start Address

The application start address must be modified to generate a bin file starting from the desired memory location,

beyond the memories taken by the bootloader.

To change the application start address, go to Project Properties > xc32-ld > Option categories: Symbols & Macros.

Users need to define the following macros:

• ROM_ORIGIN=0x430000

• ROM_LENGTH=0x1d0000

AN3475

Appendix

Application Note

DS00003475A-page 18

Figure 5-1. Project Properties

ROM Origin can be given as any address value which is beyond the size of the bootloader. ROM length can be the

size of the memory available from ROM origin to the end of the memory.

5.1.2 Generating Binary File

To generate the binary file follow these steps:

1. Go to Project Properties > Building.

2. Enable the “Execute this line after” build option, and then insert the following command:

${MP_CC_DIR}\xc32-objcopy -I ihex -O binary

"${DISTDIR}/${PROJECTNAME}.${IMAGE_TYPE}.hex"

"${DISTDIR}/${PROJECTNAME}.${IMAGE_TYPE}.bin"

AN3475

Appendix

Application Note

DS00003475A-page 19

Figure 5-2. Generating Binary File

Building the project. The bin file output can be found in the following path: <your_project>.X\dist\<config_name>

\production\

5.2 Self-Programming of Downloaded Binary

Users can download the desired application binary from any FTP server using the FTP client application

demonstrated in this document. Once the binary file is downloaded into the client file system, it can be programmed

to the MCU’s Flash memory as shown in the following flow chart.

AN3475

Appendix

Application Note

DS00003475A-page 20

Figure 5-3. Programming Binary Flow Chart

Implementation of erasing and programing the Flash sector can be found in the APP_Flash_Task() function in the

source code of this application.

Application Code Entry

Upon every reset, the bootloader code checks for the following:

• User button press (SW0)

• A valid application code in the Flash address allocated for application

If either of these conditions is true, the execution jumps to the user application code without executing the FTP client

bootloader.

AN3475

Appendix

Application Note

DS00003475A-page 21

6. References

• The Microchip TCP/IP stack:

http://ww1.microchip.com/downloads/en/appnotes/00833c.pdf

• MPLAB

Harmony v3 TCP/IP Help:

https://microchip-mplab-harmony.github.io/net/frames.html?frmname=topic&frmfile=index.html

• MPLAB Harmony v3 Installation and Usage:

https://github.com/Microchip-MPLAB-Harmony/mhc/wiki

• RFC 959:

https://tools.ietf.org/html/rfc959

• Microchip Developer Help:

https://microchipdeveloper.com/harmony3:start

• MPLAB Harmony v3:

https://www.microchip.com/mplab/mplab-harmony

• MPLAB Harmony GitHub wiki:

https://github.com/Microchip-MPLAB-Harmony/Microchip-MPLAB-Harmony.github.io/wiki

• How to Setup MPLAB Harmony v3 Software Development Framework:

http://ww1.microchip.com/downloads/en/DeviceDoc/How_to%20_Setup_MPLAB_%20Harmonyv3_

%20Software_%20Development_Framework_DS90003232A.pdf

• How to create first TCP/IP application: https://github.com/Microchip-MPLAB-Harmony/net/wiki/Create-your-first-

tcpip-pplication.

• MPLAB Harmony v2 to MPLAB Harmony v3 TCP/IP Application Migration Guide: https://github.com/Microchip-

MPLAB-Harmony/net/wiki/H2-to-H3-Migration.

AN3475

References

Application Note

DS00003475A-page 22

The Microchip Website

Microchip provides online support via our website at http://www.microchip.com/. This website is used to make files

and information easily available to customers. Some of the content available includes:

• 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 design partner 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

Product Change Notification Service

Microchip’s product change notification service helps keep customers current on Microchip products. Subscribers will

receive email notification whenever there are changes, updates, revisions or errata related to a specified product

family or development tool of interest.

To register, go to http://www.microchip.com/pcn and follow the registration instructions.

Customer Support

Users of Microchip products can receive assistance through several channels:

• Distributor or Representative

• Local Sales Office

• Embedded Solutions Engineer (ESE)

• Technical Support

Customers should contact their distributor, representative or ESE for support. Local sales offices are also available to

help customers. A listing of sales offices and locations is included in this document.

Technical support is available through the website at: http://www.microchip.com/support

Microchip Devices Code Protection Feature

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.

Legal Notice

Information contained in this publication regarding device applications and the like is provided only for your

convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with

AN3475

Application Note

DS00003475A-page 23

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 support and/or safety applications is entirely at the buyer’s risk, and the buyer agrees to defend,

indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such

use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights unless

otherwise stated.

Trademarks

The Microchip name and logo, the Microchip logo, Adaptec, AnyRate, AVR, AVR logo, AVR Freaks, BesTime,

BitCloud, chipKIT, chipKIT logo, CryptoMemory, CryptoRF, dsPIC, FlashFlex, flexPWR, HELDO, IGLOO, JukeBlox,

KeeLoq, Kleer, LANCheck, LinkMD, maXStylus, maXTouch, MediaLB, megaAVR, Microsemi, Microsemi logo, MOST,

MOST logo, MPLAB, OptoLyzer, PackeTime, PIC, picoPower, PICSTART, PIC32 logo, PolarFire, Prochip Designer,

QTouch, SAM-BA, SenGenuity, SpyNIC, SST, SST Logo, SuperFlash, Symmetricom, SyncServer, Tachyon,

TempTrackr, TimeSource, tinyAVR, UNI/O, Vectron, and XMEGA are registered trademarks of Microchip Technology

Incorporated in the U.S.A. and other countries.

APT, ClockWorks, The Embedded Control Solutions Company, EtherSynch, FlashTec, Hyper Speed Control,

HyperLight Load, IntelliMOS, Libero, motorBench, mTouch, Powermite 3, Precision Edge, ProASIC, ProASIC Plus,

ProASIC Plus logo, Quiet-Wire, SmartFusion, SyncWorld, Temux, TimeCesium, TimeHub, TimePictra, TimeProvider,

Vite, WinPath, and ZL are registered trademarks of Microchip Technology Incorporated in the U.S.A.

Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut, BlueSky, BodyCom,

CodeGuard, CryptoAuthentication, CryptoAutomotive, CryptoCompanion, CryptoController, dsPICDEM,

dsPICDEM.net, Dynamic Average Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial Programming, ICSP,

INICnet, Inter-Chip Connectivity, JitterBlocker, KleerNet, KleerNet logo, memBrain, Mindi, MiWi, MPASM, MPF,

MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation, PICDEM,

PICDEM.net, PICkit, PICtail, PowerSmart, PureSilicon, QMatrix, REAL ICE, Ripple Blocker, SAM-ICE, Serial Quad

I/O, SMART-I.S., SQI, SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC, USBCheck, VariSense,

ViewSpan, WiperLock, Wireless DNA, 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.

The Adaptec logo, Frequency on Demand, Silicon Storage Technology, and Symmcom are registered trademarks of

Microchip Technology Inc. in other countries.

GestIC is a registered trademark of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip

Technology Inc., in other countries.

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

ISBN: 978-1-5224-6113-5

Quality Management System

For information regarding Microchip’s Quality Management Systems, please visit http://www.microchip.com/quality.

AN3475

Application Note

DS00003475A-page 24

AMERICAS ASIA/PACIFIC ASIA/PACIFIC EUROPE

Corporate Office

2355 West Chandler Blvd.

Chandler, AZ 85224-6199

Tel: 480-792-7200

Fax: 480-792-7277

Technical Support:

http://www.microchip.com/support

Web Address:

http://www.microchip.com

Atlanta

Duluth, GA

Tel: 678-957-9614

Fax: 678-957-1455

Austin, TX

Tel: 512-257-3370

Boston

Westborough, MA

Tel: 774-760-0087

Fax: 774-760-0088

Chicago

Itasca, IL

Tel: 630-285-0071

Fax: 630-285-0075

Dallas

Addison, TX

Tel: 972-818-7423

Fax: 972-818-2924

Detroit

Novi, MI

Tel: 248-848-4000

Houston, TX

Tel: 281-894-5983

Indianapolis

Noblesville, IN

Tel: 317-773-8323

Fax: 317-773-5453

Tel: 317-536-2380

Los Angeles

Mission Viejo, CA

Tel: 949-462-9523

Fax: 949-462-9608

Tel: 951-273-7800

Raleigh, NC

Tel: 919-844-7510

New York, NY

Tel: 631-435-6000

San Jose, CA

Tel: 408-735-9110

Tel: 408-436-4270

Canada - Toronto

Tel: 905-695-1980

Fax: 905-695-2078

Australia - Sydney

Tel: 61-2-9868-6733

China - Beijing

Tel: 86-10-8569-7000

China - Chengdu

Tel: 86-28-8665-5511

China - Chongqing

Tel: 86-23-8980-9588

China - Dongguan

Tel: 86-769-8702-9880

China - Guangzhou

Tel: 86-20-8755-8029

China - Hangzhou

Tel: 86-571-8792-8115

China - Hong Kong SAR

Tel: 852-2943-5100

China - Nanjing

Tel: 86-25-8473-2460

China - Qingdao

Tel: 86-532-8502-7355

China - Shanghai

Tel: 86-21-3326-8000

China - Shenyang

Tel: 86-24-2334-2829

China - Shenzhen

Tel: 86-755-8864-2200

China - Suzhou

Tel: 86-186-6233-1526

China - Wuhan

Tel: 86-27-5980-5300

China - Xian

Tel: 86-29-8833-7252

China - Xiamen

Tel: 86-592-2388138

China - Zhuhai

Tel: 86-756-3210040

India - Bangalore

Tel: 91-80-3090-4444

India - New Delhi

Tel: 91-11-4160-8631

India - Pune

Tel: 91-20-4121-0141

Japan - Osaka

Tel: 81-6-6152-7160

Japan - Tokyo

Tel: 81-3-6880- 3770

Korea - Daegu

Tel: 82-53-744-4301

Korea - Seoul

Tel: 82-2-554-7200

Malaysia - Kuala Lumpur

Tel: 60-3-7651-7906

Malaysia - Penang

Tel: 60-4-227-8870

Philippines - Manila

Tel: 63-2-634-9065

Singapore

Tel: 65-6334-8870

Taiwan - Hsin Chu

Tel: 886-3-577-8366

Taiwan - Kaohsiung

Tel: 886-7-213-7830

Taiwan - Taipei

Tel: 886-2-2508-8600

Thailand - Bangkok

Tel: 66-2-694-1351

Vietnam - Ho Chi Minh

Tel: 84-28-5448-2100

Austria - Wels

Tel: 43-7242-2244-39

Fax: 43-7242-2244-393

Denmark - Copenhagen

Tel: 45-4485-5910

Fax: 45-4485-2829

Finland - Espoo

Tel: 358-9-4520-820

France - Paris

Tel: 33-1-69-53-63-20

Fax: 33-1-69-30-90-79

Germany - Garching

Tel: 49-8931-9700

Germany - Haan

Tel: 49-2129-3766400

Germany - Heilbronn

Tel: 49-7131-72400

Germany - Karlsruhe

Tel: 49-721-625370

Germany - Munich

Tel: 49-89-627-144-0

Fax: 49-89-627-144-44

Germany - Rosenheim

Tel: 49-8031-354-560

Israel - Ra’anana

Tel: 972-9-744-7705

Italy - Milan

Tel: 39-0331-742611

Fax: 39-0331-466781

Italy - Padova

Tel: 39-049-7625286

Netherlands - Drunen

Tel: 31-416-690399

Fax: 31-416-690340

Norway - Trondheim

Tel: 47-72884388

Poland - Warsaw

Tel: 48-22-3325737

Romania - Bucharest

Tel: 40-21-407-87-50

Spain - Madrid

Tel: 34-91-708-08-90

Fax: 34-91-708-08-91

Sweden - Gothenberg

Tel: 46-31-704-60-40

Sweden - Stockholm

Tel: 46-8-5090-4654

UK - Wokingham

Tel: 44-118-921-5800

Fax: 44-118-921-5820

Worldwide Sales and Service

Application Note

DS00003475A-page 25