SLAA202B February   2005  – December 2018 MSP430F149 , MSP430F149 , MSP430F2252-Q1 , MSP430F2252-Q1 , MSP430F2272-Q1 , MSP430F2272-Q1 , MSP430F2274 , MSP430F2274 , MSP430FG4619 , MSP430FG4619

 

  1.   Implementing IrDA With MSP430™ MCUs
    1.     Trademarks
    2. 1 Introduction
    3. 2 Hardware Description
      1. 2.1 Hardware Overview
      2. 2.2 Circuit Description
    4. 3 Software Description
      1. 3.1 Implementing IrPHY Layer Using Timer_A
        1. 3.1.1 Transmission
        2. 3.1.2 Reception
      2. 3.2 Implementing IrPHY Layer using USCI_A0
      3. 3.3 Implementing IrLAP
        1. 3.3.1 Discovery Services
        2. 3.3.2 Connect Services
        3. 3.3.3 Data Services
        4. 3.3.4 Disconnect Services
      4. 3.4 Implementing IrLMP
        1. 3.4.1 Discovery Services
        2. 3.4.2 Link Connect and Connect Services
        3. 3.4.3 Data Services
        4. 3.4.4 Disconnect Services
      5. 3.5 IAS Implementation
      6. 3.6 TTP Implementation
      7. 3.7 IrCOMM Implementation
      8. 3.8 Application Layer
    5. 4 PC Demonstration Application
    6. 5 IrDA Protocol Basics
      1. 5.1 Physical (IrPHY) Layer
      2. 5.2 Link Access Protocol (IrLAP) Layer
      3. 5.3 Link Management Protocol (IrLMP) Layer
      4. 5.4 Information Access Services (IAS)
      5. 5.5 Tiny Transfer Protocol (TTP)
      6. 5.6 IrCOMM
    7. 6 IrDA Communication Diagram
    8. 7 Frame Exchange Log
    9. 8 References
  2.   Revision History

3.7 IrCOMM Implementation

This is the layer that is in charge of the actual data exchange. The only times when it does not use the IrLMP services is for identifying the frames that carry user data, for constructing the frames that send data to the peer device, and when dealing with TTP services. For connection and disconnection, it uses the respective IrLMP services.

IrCOMM services are the same services as provided by the IrLMP layer. IrCOMM uses the services provided by the service layer, and this call would propagate down the protocol stack. It uses the data PDUs from IrLMP to transmit all data and control channel information. These two types of frames can be differentiated because when sending data there is an overhead of two bytes. The first byte is equal to the amount of credit that the peer has left to transmit after the data-carrying frame is received, and the second one is equal to 0 following the IrLMP LM-MUX overhead. In the case of the connection frames, a control field follows the TTP overhead where the first byte indicates the length in bytes of the connection parameters. As the connection parameters for IrLAP and TTP, these are in groups of three.