This driver implements the most common features of the Arinc 429 protocol based on PCI-400 Max Technology carrier boards and Max Technology IPM-429 modules.

What is the Arinc 429 Protocol?

Arinc 429 (also referred to as Mark 33 Digital Information Transfer System) is the most commonly used databus for commercial and transport aircraft. This specification defines the medium and data protocol used for communication between avionics equipment and systems. Arinc 429 uses a twisted, shielded pair of wires as its medium. The data flow is unidirectional in a peer to peer fashion, although up to 20 receivers can be connected on the same line. The specification also defines in details the voltage levels (differential signalling), words size and transfer rate. Messages are transmitted at a bit rate of either 12.5 or 100 kilobits per second to the receiving systems.

Arinc 429 data words are typically 32 bits and use the format shown below, which includes five primary fields, namely Parity, SSM, Data, SDI, and Label. The ARINC specification numbers the bits from 1 (LSB) to 32 (MSB). Sometimes data words have 25 bits which include 8 bits label, 16 data bits, and one parity bit.

Glossary

Supported Features

Configuring the Driver through the .config File

In the .config file, the configuration of the Arinc 429 driver as well as the specifications of each Arinc 429 word is determined for one transmission channel and one reception channel. The model should be accompanied by this file in RT-LAB when loading it. Therefore, the correct file has to be added in the model's File list window in RT-LAB as shown below in order to load the model successfully:

A simple example of .config file is given below:

opal-1.0 object
ARINC::Settings {
  ArincConf {
    channel_mute=1
    label_filter=1
    sdi_filter=1
    tx_data_format=1
    rx_data_format=1
    rx_channel=1
    tx_channel=1
    speed=1
    loopback=1
    parity=0
    parity_mode=1
    word_size=32 
    send_type=1
    interword_gap=0
    gap_selection=1
    pci_index=0
    board_type=0
    slot_id=1
    displayOnOrder=1
    encoding=0
    latched=0
    minorFrame=0
  }
  ios{
    inputs{
      ARINC::ArincPinIn{
        name=in1
        offset=0
        updateInterval=150
        startFrame=0
        label=50
        sdi=0
        labelFormat=1
        encoder{
          Arinc::arincEncoder{
            lsb=11
            msb=28
            resolution=0.100000
            min=-2000.000000
            max=12000.000000
            coding=0
            digits=0
          }
        }
      }
      ARINC::ArincPinIn{
        name=in2
        offset=1
        updateInterval=300
        startFrame=150
        label=60
        sdi=2
        labelFormat=1
        encoder{
          Arinc::arincEncoder{
            lsb=11
            msb=28
            resolution=0.005000
            min=0.000000
            max=100.000000
            coding=0
            digits=0
          }
      }	  
    }
    outputs{
      ARINC::ArincPinOut{
        name=out1
        label=51
        sdi=0
        labelFormat=1	
        decoder{
          Arinc::arincDecoder{
            lsb=11
            msb=28
            resolution=0.005000
            min=0.000000
            max=100.000000
            coding=0
            digits=0
          }
        }		
      }
      ARINC::ArincPinOut{
        name=out2
        label=61
        sdi=1
        labelFormat=1	
        decoder{
          Arinc::arincDecoder{
            lsb=11
            msb=28
            resolution=0.005000
            min=0.000000
            max=100.000000
            coding=0
            digits=0
          }
        }		
      }	  
    }
  }
}

The above-mentioned .config file can be used to send two 32 bits Arinc 429 words with labels 50 and 60 and SDIs 0 and 2 in Field-Detailed, Scheduled mode on channel one. On the receiving side, the driver awaits two 32 bits Arinc 429 words with labels 51 (sdi 0) and 61 (sdi 1).

CreateArinc.m Script File

To ease the creation of the .config file, the driver comes with a Matlab script that takes as input a Microsoft Excel datasheet. The script can be run from the Matlab command prompt by using the following command: CreateArinc('yourdata.xlsx') where yourdata.xlsx is to be replaced by the path and name of your data file (keep the single quotes). When execution is completed, the script outputs the .config file as Arinc.config and it also outputs the connections.opal file (see the Connections section for the second file). The easiest way to write your own Excel data file is to start from one of the data files that come with the example models of this driver.

The data file, unlike the .config file, can hold text instead of digital values. This makes the configuration of the driver much easier and less error-prone. The script replaces all enable, enabled, true, yes, high, in, scheduled and even by the digital value 1. So you can either use one of these keywords or simply use number 1. Similarly, the script replaces disable, disabled, false, no, low, request, out and odd by 0. So you can either use one of these keywords or simply use number 0.

The data file can be divided into two sections: a list of global parameters for the driver and details about each data words (transmitting or receiving). The global parameters can be given in any order (one per line), but if one of them is missing, Matlab will pop an error message. The following table gives a list of all the global parameters that has to be provided to the CreateArinc script:

The second section of the data file is to specify the details of each data word. The data words must be placed between the "Data{" and "Data}" lines. The line that follows "Data{" must contain the header of each data column. The columns can be in any order, but there must be no empty column between two valid columns. The headers are listed and described in the following table:

Minor/Major Frames Definition

In scheduled mode, we specify for each transmitting word three parameters for scheduling the Arinc 429 messages. These parameters are Update Interval, Offset and Start Frame. All values are in milliseconds. The minor and major frames are constructed using these parameters as well as the Minor Frame global parameter if specified by the user. If the minor frame period is not given, then it is computed using the greatest common divisor of all update intervals. The major frame is a concatenation of minor frames and represents the overall cycle of transmission. Its duration is equal to the least common multiple of the update intervals.

The Start Frame parameter determines the start “time” that a message is going to be sent inside a major frame. This “time” must be a multiple of the minor frame period. In other words, it indicates the index of the minor frame containing the message within a major frame. The Offset parameter represents the corresponding sending time offset of a message within a minor frame and it must be less than the period of the minor frame. A schematic of minor/major frame example is given below:

Connections in a .opal File

The Arinc 429 driver takes advantage of the new DIL framework. To bind Simulink signals (represented as OpInput and OpOutput blocks) to driver signals, we must define the connections in a text file named connections.opal and transfer this file with the model when loading (graphical editor will be available in a later release of RT-LAB). Below is an example of a connections.opal file:

OPAL-1.0 Object
List {
  item {
    id {
      ARINC
      Arinc.config
    }
    inputs {
      item {
        dataInExchanger=in_data[0:1]
        dataInProcess=OpInput:in_data[0:1]
        modifier=
      }
      item {
        dataInExchanger=in_label[0:1]
        dataInProcess=OpInput:in_label[0:1]
        modifier=
      }
      item {
        dataInExchanger=in_sdi[0:1]
        dataInProcess=OpInput:in_sdi[0:1]
        modifier=
      }
      item {
        dataInExchanger=in_ssm[0:1]
        dataInProcess=OpInput:in_ssm[0:1]
        modifier=
      }
      item {
        dataInExchanger=in_timeStamp[0:1]
        dataInProcess=OpInput:in_timeStamp[0:1]
        modifier=
      }		  
      item {
        dataInExchanger=in_error[0]
        dataInProcess=OpInput:in_error[0]
        modifier=
      }
    }
    outputs {
      item {
        dataInExchanger=out_chMute[0]
        dataInProcess=OpOutput:out_chMute[0]
        modifier=
      }
      item {
        dataInExchanger=out_labelFilter[0:255]
        dataInProcess=OpOutput:out_labelFilter[0:255]
        modifier=
      }
      item {
        dataInExchanger=out_sdiFilter[0:3]
        dataInProcess=OpOutput:out_sdiFilter[0:3]
        modifier=
      }
      item {
        dataInExchanger=out_data[0:1]
        dataInProcess=OpOutput:out_data[0:1]
        modifier=
      }
      item {
        dataInExchanger=out_ssm[0:1]
        dataInProcess=OpOutput:out_ssm[0:1]
        modifier=
      }
    }
  }
}

The connections.opal file presented above matches the Arinc.config file is shown before (2 data words in each direction). As for the .config file, the connections.opal file is generated from the Excel data file and CreateArinc Matlab script. It does not have to be written down manually. The same sets of global parameters and data columns are used to populate the connections.opal file as required. The description of each connection is as follows:

The Simulink Model

For the above example of Arinc.config and connections.opal, the Simulink model master subsystem would look like the following:

Making a Simulation Model with More than 1 TX and/or More than 1 RX Channel

In the case that one wants to use more than 1 TX or RX channel, then more than one Arinc.config file must be transferred to the target computer. The user shall define one Excel data file per TX/RX pair. Moreover, the global parameters, like the bus speed, must fit both TX and RX. If this is not the case, then the TX and RX channels must be split into two Arinc.config files. This is currently a limitation of the driver.

Once all the Excel data files are written, the CreateArinc script can be called on each of them successively. The script will automatically copy the output files and append a "_#", where # is a number, to the file names. For the .config files, those can be used as is in the simulation (remember to correctly fill the "Files" tab in RT-LAB). However, for the connections.opal files, the set of generated files must be merged manually into a single connections.opal file. This is because the DIL can only take one connections.opal file within a simulation execution.