IO135 - DMA Loopback

The IO135 I/O module is a fast, simultaneous-sampling, 16-bit analog input and output module, with additional individually configurable TTL digital I/O lines.

This example demonstrates how the first two inputs and outputs present on the IO135 communicate using DMA (Direct Memory Access). The model is triggered by the IO135's DMA interrupt.

Table of Contents

Setup Prerequisites Test Setup Initialize and Open the Simulink model Model Description Build, Download, and Run the Example Check the Results Additional References

Setup

Prerequisites

You will require the following to run this example:

Speedgoat real-time target machine with one IO135 I/O module installed
Connector cable from the I/O module to the terminal boards
2x 50-pin terminal boards with jumper wires

Test Setup

On the terminal board of the analog I/O module, connect the positive (+) pins of Analog Inputs 1 and 2 to the pins of Analog Outputs 1 and 2, and connect the negative (-) pins of Analog Inputs 1 and 2 to GND.

IO135 Pin Mapping

Initialize and Open the Simulink model

 
% Open Simulink model
modelName = 'sgMdl_IO135_DMALoopback';
open_system(modelName);

Model Description

The Simulink model features the IO135 Setup, IO135 Analog Input, IO135 Analog Output, IO135 Digital Input and IO135 Digital Output blocks. Analog Inputs and Outputs 1 and 2 as well as Digital Inputs and Outputs 1 and 5 are enabled in the IO135 Setup block. Furthermore, the model features a Speedgoat Interrupt Setup block, configured as model trigger. If you wish to reuse the example in a larger Simulink model, consider placing the blocks into a function-triggered subsystem and configuring the Interrupt Setup block accordingly.

Build, Download, and Run the Example

To run the example, either run the following code section or click the Run on Target button in the REAL-TIME tab in the Simulink model.

 
% Build the Simulink model
slbuild(modelName);         % this will create the real-time application file (.mldatx)
 
% Create and connect to the Speedgoat real-time target machine
tg = slrealtime;            
tg.connect;
 
% Download and install the real-time application on the target machine
tg.load(modelName); 
 
% Connect the Simulink model with external mode to the real-time application on the target machine
set_param(modelName,'SimulationMode',   'external')   % put model into External Mode
set_param(modelName,'SimulationCommand','connect')    % connect with External Mode   
 
% Start the real-time application
tg.start;
 
% Wait a few seconds and then stop the real-time application on the target machine
pause(10)
tg.stop;

Check the Results

By clicking on the scope after the model has terminated, you should be able to see the input signals of both channels.

If you zoom in horizontally, you can see the increased sample rate thanks to the active DMA on the module.

Ensure that in the scope, under View > Configuration Properties > Main, the Input Processing option is set to Columns as channels (frame based).

Documentation