Implementing IrDA With MSP430™ MCUs

The development of wireless communications has occurred rapidly throughout the past decade. One of the standards used is the Infrared Data Association (IrDA) specification. The protocol introduced by this entity consists of three basic layers: IrPHY, IrLAP, and IrLMP, which supply a base for many other applications.

This application report implements the IrDA Lite protocol (IrPHY, IrLAP, and IrLMP) on select MSP430™ microcontrollers (MCUs), as well as Tiny Transfer Protocol (TTP) and IrCOMM 3-wire services as a passive secondary-only device. IrPHY implementations are provided using a Timer_A-based approach and also using the USCI_A hardware module.

The source code and software described in this application report can be downloaded from http://www.ti.com/lit/zip/slaa202.

Trademarks

MSP430 is a trademark of Texas Instruments.

Windows is a registered trademark of Microsoft Corporation.

Sharp is a registered trademark of Sharp Microelectronics.

All other trademarks are the property of their respective owners.

1 Introduction

It is helpful if the reader of this application report has some prior knowledge of the Infrared Data Association (IrDA) specifications. Some general information on the stack is provided in Section 5 but this is by no means interchangeable with the full documentation and specifications for IrDA.

This implementation follows the standards defined by IrDA Lite. The application uses IrPHY, IrLAP, IrLMP, TTP, and IrCOMM 3-wire services to implement an IrDA serial port connection as a passive, secondary-only device. When a primary IrDA peer transmits the string "t" to the MSP430 MCU, the MCU detects the string, reads the ADC internal temperature sensor, and responds with the temperature reading. Within this application report, three different projects are included:

IrDA demonstration application running on an MSP430F149 device, using Timer_A to implement IrPHY encoding and decoding and using the ADC12 to obtain the temperature reading
IrDA demonstration application running on an MSP430FG4619 device, using USCI_A0 to implement IrPHY encoding and decoding and using the ADC12 to obtain the temperature reading
IrDA demonstration application running on an MSP430F2274 device, using USCI_A0 to implement IrPHY encoding and decoding and using the ADC10 to obtain the temperature reading

To provide a more complete solution, a demonstration application for Windows®-based PCs is also included. This application is written in the C programming language and shows how to establish an IrDA connection between a PC and the MSP430 IrDA stack using only standard Windows API calls.

2 Hardware Description

2.1 Hardware Overview

The hardware design for this application focuses on the interfacing of the MSP430F149, the MSP430FG4619, and the MSP430F2274 with the Sharp® GP2W0110YPSF IrDA transceiver device. Other MSP430 MCUs can also be used, depending on the requirements of the end application.

The Sharp GP2W0110YPSF was selected because it follows all ISO specifications for IrDA V1.0. The fact that this part can be used at a 3.0-V level is a benefit when interfacing with the MSP430 MCU, because no external circuitry is necessary to adapt the voltage levels. It also needs only three signals for interfacing with the microcontroller: transmit, receive, and shutdown. This leaves most of the MCU pins free for other purposes.

The DIr169 evaluation board is compatible with the MSP430F149-based software presented in this application report.