Managed C++/CLI

#include "string.h" //Updated Solution
    float^ f = gcnew (float);
    unsigned int^ temp = gcnew(unsigned int);
	*temp = 0;
	*temp = _byte3;
	*temp = (*temp << 8U) + _byte2;
	*temp = (*temp << 8U) + _byte1;
	*temp = (*temp << 8U) + _byte0


//	memcpy(f, temp,4U); //error


//Updated solution : 

		pin_ptr<float> pinPtr_FloatVal = &(*f);


		pin_ptr<unsigned int> pinPtr_UintVal = &(*temp);


	memcpy_s(pinPtr_FloatVal , 4U, pinPtr_UintVal , 4U); //4U i.e. 4 bytes

private: System::IO::Ports::SerialPort^ mySerialPort;

private: static System::IO::Ports::SerialPort^ mySerialPort;

System::Void MyForm::SerialPort_DataReceived(System::Object^ sender, System::IO::Ports::SerialDataReceivedEventArgs^ e)
{
    uint16_t test = 0;

    test = mySerialPort->BytesToRead;


        this->Invoke(gcnew EventHandler(this, &MyForm::ProcessReceived));

}


    System::Void MyForm::ProcessReceived(System::Object^ sender, System::EventArgs^ e) {

    // my_ReceivedData is just a custom class to parse & store received data
    my_ReceivedData^ status = gcnew my_ReceivedData;


    mySerialPort->Read(status->bytes, 0, length);
    mySerialPort->DiscardInBuffer();

    setAppearance(status->bytes);

}


public: System::Void setAppearance(array<unsigned char>^ bytes) {
    btn_Start->ImageIndex = 3; // function is excecuted, but image is still not updated from it's default
}

MyChild.h
ref class MyChild
{

       System:Void(*my_func_ptr)(int, char*);
       typedef System:Void(*MyFuncPtrType)(int, char*);
       MyFuncPtrType my_func_ptr;


	public: MyChild ( System:Void(*some_func)(int, char*)){

		my_func_ptr = some_func;
	}

	public: System::Void  Child_ButtonClicked(System::Object^ sender, System::EventArgs^ e){
		my_func_ptr();
	}

}



MyForm.h

#include "MyChild.h"

public ref class MyForm : public System::Windows::Forms::Form
{
.
.
.
	private: static System:Void test(int, char*) { //Update
		MessageBox::Show("Called from child");
	}


	private: System::Void MyForm::MyForm_Load(System::Object^ sender, System::EventArgs^ e) {
		MyChild^ child= gcnew MyChild( MyForm::test); //type incompatible error in this line
		child -> test(1,"random");
	}


}

MyChild.h
ref class MyChild
{
	   
	   
	private:     System::Void(*my_func_ptr)(int, char*);

	public:	System::Void doFunction(int A, char* B) {
           (*my_func_ptr)(A,B);
       }


	public: MyChild ( System::Void(*func)(int A, char* B)){

		my_func_ptr = func;
	}

	public: System::Void  Child_ButtonClicked(System::Object^ sender, System::EventArgs^ e){
		doFunction(1,"random");  //the arguments here are not used in later program, it is just for testing a function ptr with arguments
	}

}



MyForm.h

#include "MyChild.h"

public ref class MyForm : public System::Windows::Forms::Form
{
.
.
.

	   typedef System::Void (*callback_function)(int, char*); 
	   
	   
	private: static System:Void test(int, char*) {
		MessageBox::Show("Called from child");
	}


	private: System::Void MyForm::MyForm_Load(System::Object^ sender, System::EventArgs^ e) {
	
	
	callback_function disc;

	disc = (callback_function)(MyGUI::MyForm::test);
	
		MyChild^ child= gcnew MyChild( disc);
		child -> doFunction(1,"random");
	}


}