NEO-6M GPS connected via Arduino to Matlab

Dear all,

I have connected an NEO-6M GPS device on my Arduino UNO and I was able to retrieve the GPS data to the Serial Monitor via the arduino code ( see code ).

Now I would like to access the GPS data in Matlab. I've added the Arduino Hardware Support Package and got it working through various basic examples. But how do I access devices, like my GPS sensor, which are connected to the Arduino with a virtual serial connection?

For example; how do I set the baud rate, start the connection and how can I pull up the data with is set available by the GPS device?

The TX of the NEO-6M GPS is connected to digital port 11, while the RX is connected to digital port 10 on the Arduino.

Thanks in advance.

Answer 1

[Maitreyee Mordekar]

Hi Joppe,

The SoftwareSerial library is used to send the GPS data to the Arduino board and the Arduino board streams the same data to the PC (via the COM port). This data on the system's COM port is the one that is displayed when the Serial Monitor window is opened using the Arduino IDE.

Thus, to fetch the required data from Arduino, one will have to just read from the COM port to which the Arduino is connected. You can follow the procedure mentioned below fetch the data from the GPS sensor using Arduino-

1. You will, thus, have to declare a serial port using the serial command and set the specified properties.
2. Also, you can change the properties of the serial port using the set(serial) function.
3. The following step will be to connect the serial port object to the device using fopen(serial) function.
4. The below function fgets(serial) will help you fetch the file string, i.e., the NMEA strings that are obtained from the GPS sensor.
5. The next step will be to disconnect the serial port object from the device using the fclose(serial) function.
6. The final step will be to delete the serial object from the workspace using the delete(serial) function.

An example code snippet that will yield the NMEA strings on MATLAB is as below.

s=serial('COM4', 'InputBufferSize', 600, 'BaudRate', 9600); % Create a serial object with specified properties
set(s,'Terminator','CR/LF') ; % Set the Terminator Character
fopen(s); % Open the serial port
i=1;
data = cell(0);
while(i<=17) % Read 17 lines
    if (s.BytesAvailable) % Check if bytes are available in the buffer
        data{i}=char(fgets(s)); % Read the data and convert ASCII to character
        i=i+1; % Increment the counter
  end
end
fclose(s); % Disconnect the serial port object from the device
delete(s); % Delete the serial object

Note that, the COM port that was allocated to the Arduino was 'COM4' on my machine. This parameter value will change depending on the COM port that Arduino is assigned on the user's system.

Since, from the link provided, the number of lines at the output of the Serial Monitor is seventeen, the counter has been set to 17 (This includes the blank lines). However, this code can be customized depending on the requirement.

Thus, the 'data' cell array will hold the strings that are fetched by reading each line from the 'COM4' port.

[Walter Roberson]

I wonder if you could discuss when to connect with an arduino with a arduino() call, and when to connect to the serial port directly to to communicate with the arduino?

[Maitreyee Mordekar]

Hi Walter,

Using the read from the serial, we will just be able to read what is being printed on the Serial Monitor by the Arduino. This would not allow us to change/manipulate settings of the pins directly. arduino() function is required when the pins are needed to be changed.

I hope that helps.

[Amir Mehdi Yazdani]

Dear Maitreyee Mordekar

Thanks for your useful post. Can you offer some direction to read NMEA GPS data on serial port of Raspberry Pi 3?

Cheers

Amir