User manual

LPCXpresso Experiment Kit - User’s Guide

Page 128

7.19 Extra: Work with USB Host

In this experiment you will learn how to work with an USB host interface. This experiment requires the

LPCXpresso LPC1769 board, which has an USB Host interface.

7.19.1 Lab 18a: USB Host

Using the USB Host interface of the LPC1769 it is possible to read/write from a USB Memory Stick.

This has a wide range of uses, including

 Providing files for a web server

 Data logging

 Storing of initialization data

The data on the memory stick is persistent, allowing states and data to be kept between power cycles.

This experiment is based on the USBHostLite project that is part of the software package distributed

with the LPCXpresso IDE. It expects an msread.txt file (content not important) to be present in the

root of the memory stick's file system. The file will be copied into (possibly overwriting) mswrite.txt.

The memory stick should be formatted as FAT.

Note that an external +5V supply is needed, either via J1 or J17. Also note that two jumpers shall be

inserted in J11, pos 1-2 and 3-4.

This experiment is based on the code examples that are delivered with the LPCXpresso IDE. The code

is structured very differently (none of the code from the previous exercises is used). You have to create

a new workspace in LPCXpresso and then import the projects from Lab18a.zip.

Insert a USB memory stick in the J10 connector and then start the program. The program uses

semihosting so all printouts will be available in the LPCXpresso IDE. If the memory stick is found and

the file is copied the printouts should look like this:

Initializing Host Stack

Host Initialized

Connect a Mass Storage device

Mass Storage device connected

Copying from MSREAD.TXT to MSWRITE.TXT...

Copy completed

If the memory stick was not inserted before the program started it will look like this:

Initializing Host Stack

Host Initialized

Connect a Mass Storage device

ERROR: In Host_EnumDev at Line 407 - rc = -1

This is not very user friendly. Improve the implementation of main() to wait for the memory stick to be

inserted, copy the file, wait for the memory stick to be removed and then start over.