MATLAB and Arduino Communications

Hello Everyone,

So I am working on a robotics project that has two levels of control. The main control algorithms are written in MATLAB and lower-level control is developed to control driving and steering motors using Arduino.

The Matlab sends steering and speed commands to Arduino and using that Arduino will run the robot. Now everything is working fine on MATLAB end and it sends the commands but the Arduino is only processing the first command and doesn't run the following commands.

Also, sometimes I get an error on MATLAB saying a timeout occurred during write operation. Now I researched about it and basically the read operation started before the write function could complete. How can I overcome this problem?

Here is MATLAB code:

function [ ard_serial_port, Error ] = setup_arduino( device_port )
% concatenation preserves whit space instead of strcat
PROMPT01 = ['Please enter COM port # (1 for COM1, etc.) for Arduino'];
TITLE01 = 'COM port';

Error = false;

ard_serial_port = '';
% Use the default port for the device you're using in your pc:
ComNum = char(inputdlg(PROMPT01, TITLE01, 1, {num2str(device_port)}));

if isstrprop(ComNum, 'digit')
    % Create a serial port object.
    ard_serial_port = instrfind('Type', 'serial', 'Port', strcat('COM', ComNum), 'Tag', '');

    % Create the serial port object if it does not exist 
    % otherwise use the object that was found.
    if isempty(ard_serial_port)
        ard_serial_port = serial(strcat('COM', ComNum));     % Create serial object (PORT Dependent)
    else
        fclose(ard_serial_port);
        ard_serial_port = ard_serial_port(1);
    end

    % Number of bytes in inout buffer
%     ard_serial_port.InputBufferSize = 512;
    ard_serial_port.BaudRate = 38400;
    ard_serial_port.DataBits = 8;
    ard_serial_port.StopBit = 1;
    ard_serial_port.Timeout = 5;
    ard_serial_port.Parity = 'none';
    ard_serial_port.StopBits = 2;
    ard_serial_port.BytesAvailableFcnMode = 'terminator';
    ard_serial_port.Terminator = 'CR/LF';
    try
        % Connect to the instrument, Open the serial port for r/w
        fopen(ard_serial_port);
    catch exception
        fprintf(['\n' exception.message '\n']);
        h = msgbox(exception.message);
        Error = true;
    end
else
    fprintf('\nInvalid COM port  for Arduino selected\n');
%     msgbox('Invalid COM port selected.');
    Error = true;
end

And here is code to send commands to Arduino

function [control_command] = serial_write_master_arduino(ard_serial_port, delta_master, speed_ref)

control_command = sprintf('%f,%f$', delta_master, speed_ref)
fprintf(ard_serial_port, control_command);

end

Answer 1

[Namnendra]

Hello Kishita,

It sounds like you're encountering a couple of issues with the serial communication between MATLAB and Arduino. Let's address the problems one by one:

Problem 1: Arduino Only Processes the First Command

This issue might be due to how the Arduino is handling incoming serial data. Ensure that the Arduino code is structured to continuously read from the serial buffer and process each command. Here are some tips:

1. Arduino Code: Make sure the Arduino is set up to read until a specific terminator (like `$`) and then process the command. Here's a basic structure for the Arduino code:

void setup() {
      Serial.begin(38400);
    }

    void loop() {
      if (Serial.available() > 0) {
        String command = Serial.readStringUntil('$'); // Read until the terminator
        // Process the command here
        // Example: parse and execute the command
      }
    }

2. Clear the Buffer: Ensure the Arduino is clearing the buffer after processing each command to avoid overflow or incorrect reads.

3. Flow Control: Consider implementing a simple handshake mechanism where the Arduino sends back an acknowledgment after processing a command, and MATLAB waits for this acknowledgment before sending the next command.

Problem 2: MATLAB Timeout During Write Operation

The timeout error suggests that the write operation might be blocking or taking too long. Here are some suggestions to mitigate this:

1. Increase Timeout: You can try increasing the `Timeout` property in MATLAB to give more time for the operation to complete:

ard_serial_port.Timeout = 10; % Increase this value as needed

2. Flush the Output Buffer: Before sending a new command, ensure the output buffer is clear.

3. Check for Acknowledgment: Modify your MATLAB script to wait for an acknowledgment from Arduino before sending the next command:

function [control_command] = serial_write_master_arduino(ard_serial_port, delta_master, speed_ref)
        control_command = sprintf('%f,%f$', delta_master, speed_ref);
        fprintf(ard_serial_port, control_command);
        
        % Wait for acknowledgment
        ack = fscanf(ard_serial_port);
        if ~strcmp(ack, 'ACK') % Replace 'ACK' with your actual acknowledgment
            error('No acknowledgment received from Arduino');
        end
    end

4. Error Handling: Implement error handling to retry sending commands if a timeout occurs.

General Tips

- Debugging: Use serial monitors or print statements in Arduino to debug and ensure commands are being received correctly.

- Synchronization: Ensure that both systems (MATLAB and Arduino) are synchronized in terms of baud rate and terminators.

- Testing: Test with simple commands first to ensure basic communication works before moving on to more complex commands.

By addressing these areas, you should be able to improve the reliability of the communication between MATLAB and Arduino.

Thank you.

[Mohammed Yakoob]

Hello dear, Please I need to know how to clear the internal buffers when I have been using the arduino() class to connect with??