serial communication problem between Arduino and pc

Question

1.00/5 (1 vote)

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In both codes following, I expect that PC print "3". but PC print like below screenshot.
Why like this? How do I get "3"? plz help me.

Arduino

int sign;
void setup()
{
  Serial.begin(9600); //시리얼 포트 열기, 속도 9600
}
void loop()
{
  sign=3;
  Serial.write(sign);
  delay (1000);
}

PC

#include<stdio.h>
#include<windows.h>
#include<winbase.h>
int main()
{
 char szPort[15];  
 wsprintf(szPort, "COM%d", 3); 
 HANDLE  m_hComn = NULL;  
 m_hComn = CreateFile(szPort, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    
 if (m_hComn == INVALID_HANDLE_VALUE)  
 {
  printf("(!) Failed to create a  Comm Device file \n");
  return FALSE;   
 }
 DCB dcb;       
 dcb.DCBlength = sizeof(DCB); 
 GetCommState(m_hComn, &dcb);    
 dcb.BaudRate = 9600;
 dcb.ByteSize = 8;
 dcb.Parity = 0;
 dcb.StopBits = 0;
 SetCommState(m_hComn, &dcb); 

 OVERLAPPED  osRead;
 osRead.Offset = 0;
 osRead.OffsetHigh = 0;
 osRead.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

 int buf ; //

 while (1)
 {
  ReadFile(m_hComn, &buf,sizeof(buf), NULL, &osRead);
  printf("%d \n", buf);
 }
 
 CloseHandle(m_hComn);  
 return 0;
}

Posted 20-Jan-16 3:58am

Member 12160760

Updated 20-Jan-16 4:18am

jeron1

v2

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jeron1 20-Jan-16 10:20am

There is no screen shot, what is the output?

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CPallini · Accepted Answer · 2016-01-20T05:35:00

Your Arduino code sends a byte at time (see Arduino - Write[^]), so your PC code should read a single byte and output it (it could optionally read multiple bytes, buffer and then output all of them), so the proper call to ReadFile (I hardly believe you need the OVERLAPPED struct in such a simple scenario) is:

C++

unsigned char c;
DWORD dwRead;
if ( ReadFile( hComm, &c, sizeof(c), &dwRead, NULL) )
{
  if ( dwRead == 1)
    printf("%d\n", (int) c);
}
else
{// handle error
}