Simulink

Communicating with Arduino® Mega 2560 Hardware

This example shows how to tune the parameters and monitor the signals of an algorithm running on Arduino Mega 2560 board.

Introduction

Simulink Support Package for Arduino Hardware enables you to monitor and tune algorithms running on Arduino Mega 2560 board from the same Simulink® models from which you developed the algorithms.

In this example you will learn how to tune and monitor the algorithm in real time as it is executing. When you are developing algorithms, it is often necessary to determine appropriate values of critical algorithm parameters in an iterative fashion. For example, a surveillance algorithm that measures motion energy in a room may use a threshold to determine an intruder in the presence of ambient noise. If the threshold value is set too low, the algorithm may erroneously interpret any movement as an intruder. If the threshold value is set too high, the algorithm may not be able to detect any movement at all. In such cases, the right threshold value may be obtained by trying different values until the desired algorithm performance is reached. This iterative process is called parameter tuning.

Simulink's External mode feature enables you to accelerate the process of parameter tuning by letting you change certain parameter values while the model is running on target hardware, without stopping the model. When you change parameter values from within Simulink, the modified parameter values are communicated to the target hardware immediately. The effects of the parameters tuning activity may be monitored by viewing algorithm signals on scopes or displays in Simulink.

This example introduces the Simulink External mode feature by showing you how to:

  • Set up communication between Simulink and Arduino Mega 2560 board.

  • Use a Simulink model to tune the parameters of an algorithm that is running on Arduino Mega 2560 board.

  • Use Simulink scopes to monitor the state of an algorithm running on Arduino Mega 2560 board.

Prerequisites

We recommend completing Getting Started with Arduino Mega 2560 HardwareGetting Started with Arduino Mega 2560 Hardware example.

Required Hardware

To run this example you will need the following hardware:

  • Arduino Mega 2560 board

  • USB cable

  • LED

  • 220 Ohm resistor

  • Breadboard wires

  • Small breadboard (recommended)

Task 1 - Connect an LED to the Arduino Output Pin

In this task, you will connect an LED to an Arduino digital output pin so you can see changes in the logical state of the pin.

1. Attach one end of the 220 Ohm resistor to digital output pin 9 on the Arduino Mega 2560 board. Use the recommended breadboard and the breadboard wires.

2. Attach the long leg (positive) of the LED to the resistor. Attach the short leg (negative) to the ground pin on the Arduino Mega 2560 board.

Task 2 - Simulate the Model

To simulate the model, follow these steps:

1. Open the Communicating with Arduino Mega 2560 HardwareCommunicating with Arduino Mega 2560 Hardware model.

2. Observe that the model plays the motion energy recorded in a room and compares it with a threshold to detect intrusion.

3. In the model, change the Simulation mode on the toolbar to Normal. This tells Simulink to run the model on the host computer. See Task 3 below to run the model on the Arduino target hardware.

4. In the model, click the Run button in the Simulink toolbar.

5. Click the Scope block. Observe that the algorithm detects multiple intrusions.

6. Click Stop button in the Simulink model.

Task 3 - Run the Model in External Mode

1. Connect a USB cable from your computer to the Arduino Mega 2560 board.

2. In the model, change the Simulation mode on the toolbar to External.

3. In the model, click the Run button on the toolbar.

Task 4 - Communicate with the Model

At this point, your model is running on Arduino Mega 2560 board. As the model runs on hardware, it communicates with Simulink model in External mode using serial connection over USB.

1. Notice that the LED attached to pin 9 is glowing almost constantly. This means that the selected threshold is too low and that the algorithm misinterprets even a minor motion energy change as an intrusion. You need to find a more optimal value of the threshold.

2. Double-click the Threshold block in the model, increase its value, and click OK or Apply. This changes the threshold value in the model running on the board.

3. Check whether the glowing pattern of the LED has changed. The LED should light up every 10 and 11.5 seconds in a correctly tuned algorithm.

4. If there is no change in LED light pattern, repeat the Steps 2 and 3 until you find the right value of the threshold.

5. Click Stop button in the Simulink model.

Task 4 - Configure the Model to Run in External Mode over TCP/IP

Refer to the documentation section: Configure the model to run in External Mode over TCP/IPConfigure the model to run in External Mode over TCP/IP.

Task 5 - Configure the Model to Run in External Mode over WiFi

Refer to the documentation section: Configure the model to run in External Mode over WiFiConfigure the model to run in External Mode over WiFi.

Other Things to Try

  • Monitor other signals in the model. For example, add another scope to monitor the value of the recorded motion energy.

  • Improve the detection algorithm to filter out any motion energy changes that are shorter than 0.2 seconds.

Summary

This example showed a workflow for tuning and monitoring an algorithm running on Arduino Mega 2560 board. In this example you learned:

  • How to tune an algorithm parameter on Arduino Mega 2560 board using the External mode feature.