Обмен данными с устройством через com-порт

private void serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            byte[] b = new byte[128];
            target_port.Read(b, 0, b.Length);
            string s = Encoding.ASCII.GetString(b);
 
            richTextBox1.AppendText(s);
        }

this.target_port.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(serialPort_DataReceived);

private void Start_work_Click(object sender, EventArgs e)
        {
            if (target_port.IsOpen)
            {
                target_port.Write("load on ;");
 
                int index = 0;
                process_work(index);
                control_tab.SelectedIndex = 0;
            }
            else
            {
                control_tab.SelectedIndex = 2;
                qDebug.Items.Add(DateTime.Now.ToLongDateString() + " " + DateTime.Now.ToLongTimeString() +
                        " >> " + "Устройство не доступно! Проверьте подкючение..." + "\n");
            }

 private void button1_Click(object sender, EventArgs e)
        {
            target_port.Write("load ;");
        }

/* Link this program with appropriate *cib*.obj. */  
/* This application program is written in TURBO C 2.0 for the IBM PC-AT compatible. The National Instruments Cooperation (NIC) Model PC-2A board provides the interface between the PC-AT and a PRODIGIT MPAL ELECTRONIC LOAD. The appropriate *cib*.obj file is required in each program to properly link the NIC board to C LANGUAGE. and include the <decl.h.> HEADER FILE to C LANGUAGE. */  
#include <stdio.h> 
#include <dos.h> 
#include <math.h> 
#include "decl.h" /* NI GPIB CARD HEADER FILE */  
main() 
{    char ouster[20],rdbuf[15],spec[10];    
int i,ch,load;
 /* Assign unique identifier to the device "dev5" and store in variable load. check for error. ibfind error = negative value returned. */   
 if((load = ibfind("dev5")) < 0) /*  Device variable name is load  */      
{    /*  GPIB address is  5  */        
printf("\r*** INTERFACE ERROR ! ***\a\n");        
printf("\r\nError routine to notify that ibfind failed.\n");        
printf("\r\nCheck software configuration.\n");        
exit(1);      
} 
/*  Clear the device  */   
 if((ibclr(load)) & ERR);     
 {        
printf("INTERFACE ERROR ! \a");        
exit(1);     
 }    
clrscr();
 /* Clear load error register */   
 for(i=1,ch=0;i<=4;i++,ch++)    
 {      
outstr=chan[ch];     
 ibwrt(load,outstr,6);     
 ibwrt(load,"CLER",4);     
 }
  ibwrt( load,"NAME?",5);  /*  Get the 3310 series module load specification  */    
strset(rdbuf,'\0');   /*  Clear rdbuf string buffer  */    
strset(spec,'\0');   /*  Clear spec string buffer  */    
ibrd(load,spec,20);   
 if (spec[3] == '9')      
 printf("\n 3300F series specification error !");
 /*  Set the channel 1, preset off, current sink 1.0 amps and load on commands to the load. */   
 ibwrt( load,"chan 1;pres off;curr:low 0.0;curr high 1.0;load on ",51);  
  ibwrt( load,"meas:curr ?",11); 
/*  Get the load actially sink current from the load  */ 
  ibrd( load,rdbuf,20);
 /*  go to local.  */    
ibloc(load); 
}

string str ="NAME?";
byte[] outBytes = Encoding.UTF8.GetBytes(str);
target_port.Write(outBytes, 0, outBytes.Length);

private void button1_Click(object sender, EventArgs e)
        {
            string stat_load = "MODE?;";
            byte[] outButes = Encoding.UTF8.GetBytes(stat_load);
            target_port.Write(outButes, 0, outButes.Length);
        }

 private delegate void setTextDelegate(string text);
        // получение ответов от порта;
        private void serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            byte[] b = new byte[128];
            target_port.Read(b, 0, b.Length);
            string s = Encoding.ASCII.GetString(b);
 
            this.BeginInvoke(new setTextDelegate(data_received), new object[] { s });
        }
        private void data_received(string data)
        {
            richTextBox1.AppendText(data);
        }