Connecting Arduino to App Designer with Drop Down and Button

I want to connect my Arduino to App Designer by using the "drop down" list. This is what my app looks like:

First, I am looking for if there is any serial com. system. And I am writing them to Drop Down.

p = instrhwinfo('serial');

app.SerialPortsDropDown.Items = p.AvailableSerialPorts;

After this I have planned to read the serial port that is shown in the Drop Down and write it to serialport()

app.a = serialport(app.SerialPortsDropDown.value,9600);

Unfortunately these lines did not work. The error message I got:

Error using serialport (line 116) Unable to connect to the serialport device at port 'COM9'. Verify that a device is connected to the port, the port is not in use, and all serialport input arguments and parameter values are supported by the device.

So, the first two lines of code work. I am able to see COM9 (the com my arduino connected) in the drop-down list. This shows there is a serial port at COM9. But when it comes to reading it with app.a = serialport(app.SerialPortsDropDown.value,9600); it gives error.

How can I connect a serial port via the MATLAB App-designer?

[Abdulkadir Arslan]

I guess I solved the problem.

I added the following lines before to declare app.a:

clear a; 

if ~isempty(instrfind)
    fclose(instrfind);
    delete(instrfind);
end

These a few lines clears the serial coms. that are connected to a before.

But the problem continues. Now I cannot use connected serial port.

App Designer does not run this simple code line:

 writeDigitalPin(app.a,'D3',1);

It is giving this error:

 Error Undefined function 'writeDigitalPin' for input arguments of type 'internal.Serialport'.
 

Any idea about the problem ?

Answer 1

[Walter Roberson]

writeDigitalPin only applies arduino objects. You need to arduino() the serial port, not serialport() it.