Use serial port object in C++ file

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Hi there,

I am writing a C++ application to send data down a serial port. My problem arises when I attempt to create a file with all my commands in and link that to my main file. I need to access the serialport1 object defined here in my main form "Communicate.h" (I changed the scope from private to public):

C++

public: System::IO::Ports::SerialPort^  serialPort1;

I need to access this in Commands.cpp I try it like this:

C++

#include "Commands.h"
#include "Communicate.h"

using namespace SerialCommunications;
using namespace System;
using namespace System::IO::Ports;

void elbow(int dir, int amt)
{
    array<Byte>^ cmd = { 0xff, 0xff, 0xff };
    Communicate::serialPort1->Write(cmd, 0, 3);
}

However I just get this error message trying to access it:

"Error: a nonstatic member reference must be relative to a specific object"

Thanks in advance!!
Max

Posted 14-Jun-15 10:28am

MRichards29

Updated 14-Jun-15 21:34pm

nv3

v3

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nv3 15-Jun-15 3:36am

Looks like you have to instantiate the serialPort1 object first.

2 solutions

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User 59241 · Answer 1 · 2015-06-14T13:47:00

There is no serialport object defined yet. Somewhere you need

C#

// Create a new SerialPort object with default settings.
serialPort1 = gcnew System::IO::Ports::SerialPort();

Refer to the example here:

https://msdn.microsoft.com/en-us/library/system.io.ports.serialport(v=vs.110).aspx?cs-save-lang=1&cs-lang=cpp#code-snippet-1[^]

Maybe move the declaration to the class and instantiate it in the constructor.

[Edit]
Without your code I have no idea. First and most importantly I would ask why you are using C++/clr and not C#.
Here is a simple example JUST to show you the mechanism.

communicate.h

C++

using <System.dll>

using namespace System;
using namespace System::IO::Ports;

namespace SerialCommunications
{
	ref class communicate
	{
	public:
		communicate(void)
		{
			// Create a new SerialPort object with default settings.
			serialPort1 = gcnew SerialPort();
		};

	private:
		SerialPort^ serialPort1;
	public:

		void Write(array<unsigned char> ^ buffer, int offset, int count)
		{
			serialPort1->Write(buffer, offset, count);
		}
	};
}

then

C++

/ testclr.cpp : main project file.

#include "stdafx.h"
#include "communicate.h"

using namespace System;
using namespace SerialCommunications;

int main(array<System::String ^> ^args)
{
    communicate^ myCommunicate = gcnew communicate();

    array<Byte>^ cmd = gcnew array<Byte>{ 0xff, 0xff, 0xff };
    myCommunicate->Write(cmd, 0, 3);


    return 0;
}

MRichards29 · Answer 2 · 2015-06-16T08:11:00

Solution 2

Thank you very much for your response! I have managed to fix the issue by changing the:

public: System::IO::Ports::SerialPort^  serialPort1;

to:

public: static System::IO::Ports::SerialPort^  serialPort1;

Thank you very much,
Max

Posted 16-Jun-15 8:11am

MRichards29

Comments

Philippe Mori 16-Jun-15 19:51pm

Usually, you want to avoid static variable as it can make the code harder to reuse in another context.