MATLAB Support Package for Arduino Hardware (Changing the pin mode on "Aref")

Hello! Im using Matlab for my Master Thesis. The circuit I am using is a differential amplifier circuit, which requires me to use the bias voltage as the Analog referance on the arduino, so I can use the whole ADC range when sampling. I've been researching this problem for a few weeks, looking through old source/server codes for the Arduino, and I can't seem to find a solution (I did find this old arduino object code).

There was another thread on using the "srv.pde" from Adafruit Motor shield libraries (AFmotor). This file can't be located.

My conclusion is that the arduino object needs to be rewritten with the option to write 'external' to pinMode through the fwrite in MATLAB. Is there someone that have come across a solution of this?

My main question is: How can you change the pin mode of "Aref" to 'external' in MATLAB?

In MWProtocol.m, I found:

function value = readVoltage(obj, pin, aref)   
            msg = [...
            obj.READ_VOLTAGE;
            pin
            ];  
            value = sendMWMessage(obj, msg);
            value = (bitshift(value(2), 8) + value(3))/1023*aref;
end

Does this mean I can pass 'external' in the readVoltage function? And if so, how can I use the readVoltage function from the MWProtocol class?

Addons:

• MATLAB Support Package for Arduino Hardware
• Adafruit\MotorshieldV2

Board:

• Arduino UNO
• MUX shield

Thank you very much in advance.