Originally Posted by prashw

hey all.........i m new here!!!!!!

I am at my wits end on this problem.....i would appreciate it if you could give any help.....................................................

i managed to compile and run a C++ program that intializes and reads/writes to a serial port . I was using the Dev C++ compiler to write the code.


Now I am trying to verify the output.What I did was to write the letter 'a' to the serial port. The serial port is connected to a digital oscilloscope and I intend to see the voltage patterns that correspond to the letter 'a' as below.

11 01000001 0 = stop bits / data bits / start bit


But this voltage pattern is not shown in the oscilloscope. Instead I only see the handshaking signal (a data bit '1') coming from the serial port.( I was able to see the handshaking control signal/initializing signal but not the data signal (the data signal was the letter 'a') ).
I saw a '1' from pin 3 and pin 6 of the R232 serial port when I ran the program. These pins correspond to Transmit data, Data set ready signals that are sent from the laptop to the oscilloscope.

1. I cannot see any data signals corresponding to the letter 'a'. What is the reason behind this????
Is it because there is no reply from the oscilloscope for the handshaking signal the laptop sends to it?? (i am using a laptop to run the program)
(Meaning the oscilloscope fails to send a handshking signal back to the laptop......this might indeed be the case because oscilloscopes are not built to send handshking signals)

2.If so how can I bypass sending handshking signals and simply send the letter 'a' to the oscilloscope and view its voltage pattern???

3.Can I do this by a simple adjustemnt to the code I have written below????



I would greatly appreciate any help u guys can give....

the code is below (compiles without errors on Dev C++ )

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Serial.h
CODE
CODE// Flow control flags
 
#define FC_DTRDSR 0x01
#define FC_RTSCTS 0x02
#define FC_XONXOFF 0x04
 
// ascii definitions
#include <stdio.h>
#include <time.h>
 
//#define VC_EXTRALEAN // Exclude rarely-used stuff from Windows headers
#include <string.h>
 
#define ASCII_BEL 0x07
#define ASCII_BS 0x08
#define ASCII_LF 0x0A
#define ASCII_CR 0x0D
#define ASCII_XON 0x11
#define ASCII_XOFF 0x13
 
 
HANDLE SerialInit(char*, int); 
 
char SerialGetc(HANDLE*);
 
void SerialPutc(HANDLE*, char);
 
 
--------------------------------------------------------------------------
 
 
Serial.cpp
CODE
CODE
#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <time.h>
#include <windows.h>
#include <string.h>
#include "serial.h"
 
// Flow control flags
 
#define FC_DTRDSR 0x01
#define FC_RTSCTS 0x02
#define FC_XONXOFF 0x04
 
// ascii definitions
 
#define ASCII_BEL 0x07
#define ASCII_BS 0x08
#define ASCII_LF 0x0A
#define ASCII_CR 0x0D
#define ASCII_XON 0x11
#define ASCII_XOFF 0x13
using namespace std;
// variables used with the com port
BOOL bPortReady;
DCB dcb;
COMMTIMEOUTS CommTimeouts;
BOOL bWriteRC;
BOOL bReadRC;
DWORD iBytesWritten;
DWORD iBytesRead;
 
HANDLE SerialInit(char *ComPortName, int BaudRate) 
{
HANDLE hCom;
 
hCom = CreateFile(ComPortName, 
GENERIC_READ | GENERIC_WRITE,
0, // exclusive access
NULL, // no security
OPEN_EXISTING,
0, // no overlapped I/O
NULL); // null template 
 
bPortReady = SetupComm(hCom, 2, 128); // set buffer sizes
 
 
bPortReady = GetCommState(hCom, &dcb);
dcb.BaudRate = BaudRate;
dcb.ByteSize = 8;
dcb.Parity = NOPARITY;
// dcb.Parity = EVENPARITY;
dcb.StopBits = ONESTOPBIT;
dcb.fAbortOnError = TRUE;
 
// set XON/XOFF
dcb.fOutX = FALSE; // XON/XOFF off for transmit
dcb.fInX = FALSE; // XON/XOFF off for receive
// set RTSCTS
dcb.fOutxCtsFlow = TRUE; // turn on CTS flow control
dcb.fRtsControl = RTS_CONTROL_HANDSHAKE; // 
// set DSRDTR
dcb.fOutxDsrFlow = FALSE; // turn on DSR flow control
dcb.fDtrControl = DTR_CONTROL_ENABLE; // 
// dcb.fDtrControl = DTR_CONTROL_DISABLE; // 
// dcb.fDtrControl = DTR_CONTROL_HANDSHAKE; // 
 
bPortReady = SetCommState(hCom, &dcb);
 
// Communication timeouts are optional
 
bPortReady = GetCommTimeouts (hCom, &CommTimeouts);
 
CommTimeouts.ReadIntervalTimeout = 5000;
CommTimeouts.ReadTotalTimeoutConstant = 5000;
CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
CommTimeouts.WriteTotalTimeoutConstant = 5000;
CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
 
bPortReady = SetCommTimeouts (hCom, &CommTimeouts);
 
return hCom;
}
 
char SerialGetc(HANDLE *hCom)
{
char rxchar;
BOOL bReadRC;
static DWORD iBytesRead;
 
bReadRC = ReadFile(*hCom, &rxchar, 1, &iBytesRead, NULL);
 
return rxchar;
}
 
void SerialPutc(HANDLE *hCom, char txchar)
{
BOOL bWriteRC;
static DWORD iBytesWritten;
 
bWriteRC = WriteFile(*hCom, &txchar, 1, &iBytesWritten,NULL);
 
return;
}
 
int main()
{
HANDLE my=SerialInit("com1",1200);
char letter;
 
HANDLE *ptr;
*ptr=my;
SerialPutc(ptr,'a'); 
//letter=SerialGetc(ptr);
getch(); 
 
return 0;
 
}

Serial.h CODE CODE// Flow control flags #define FC_DTRDSR 0x01 #define FC_RTSCTS 0x02 #define FC_XONXOFF 0x04 // ascii definitions #include <stdio.h> #include <time.h> //#define VC_EXTRALEAN // Exclude rarely-used stuff from Windows headers #include <string.h> #define ASCII_BEL 0x07 #define ASCII_BS 0x08 #define ASCII_LF 0x0A #define ASCII_CR 0x0D #define ASCII_XON 0x11 #define ASCII_XOFF 0x13 HANDLE SerialInit(char*, int); char SerialGetc(HANDLE*); void SerialPutc(HANDLE*, char); -------------------------------------------------------------------------- Serial.cpp CODE CODE #include <iostream> #include <conio.h> #include <stdio.h> #include <time.h> #include <windows.h> #include <string.h> #include "serial.h" // Flow control flags #define FC_DTRDSR 0x01 #define FC_RTSCTS 0x02 #define FC_XONXOFF 0x04 // ascii definitions #define ASCII_BEL 0x07 #define ASCII_BS 0x08 #define ASCII_LF 0x0A #define ASCII_CR 0x0D #define ASCII_XON 0x11 #define ASCII_XOFF 0x13 using namespace std; // variables used with the com port BOOL bPortReady; DCB dcb; COMMTIMEOUTS CommTimeouts; BOOL bWriteRC; BOOL bReadRC; DWORD iBytesWritten; DWORD iBytesRead; HANDLE SerialInit(char *ComPortName, int BaudRate) { HANDLE hCom; hCom = CreateFile(ComPortName, GENERIC_READ | GENERIC_WRITE, 0, // exclusive access NULL, // no security OPEN_EXISTING, 0, // no overlapped I/O NULL); // null template bPortReady = SetupComm(hCom, 2, 128); // set buffer sizes bPortReady = GetCommState(hCom, &dcb); dcb.BaudRate = BaudRate; dcb.ByteSize = 8; dcb.Parity = NOPARITY; // dcb.Parity = EVENPARITY; dcb.StopBits = ONESTOPBIT; dcb.fAbortOnError = TRUE; // set XON/XOFF dcb.fOutX = FALSE; // XON/XOFF off for transmit dcb.fInX = FALSE; // XON/XOFF off for receive // set RTSCTS dcb.fOutxCtsFlow = TRUE; // turn on CTS flow control dcb.fRtsControl = RTS_CONTROL_HANDSHAKE; // // set DSRDTR dcb.fOutxDsrFlow = FALSE; // turn on DSR flow control dcb.fDtrControl = DTR_CONTROL_ENABLE; // // dcb.fDtrControl = DTR_CONTROL_DISABLE; // // dcb.fDtrControl = DTR_CONTROL_HANDSHAKE; // bPortReady = SetCommState(hCom, &dcb); // Communication timeouts are optional bPortReady = GetCommTimeouts (hCom, &CommTimeouts); CommTimeouts.ReadIntervalTimeout = 5000; CommTimeouts.ReadTotalTimeoutConstant = 5000; CommTimeouts.ReadTotalTimeoutMultiplier = 1000; CommTimeouts.WriteTotalTimeoutConstant = 5000; CommTimeouts.WriteTotalTimeoutMultiplier = 1000; bPortReady = SetCommTimeouts (hCom, &CommTimeouts); return hCom; } char SerialGetc(HANDLE *hCom) { char rxchar; BOOL bReadRC; static DWORD iBytesRead; bReadRC = ReadFile(*hCom, &rxchar, 1, &iBytesRead, NULL); return rxchar; } void SerialPutc(HANDLE *hCom, char txchar) { BOOL bWriteRC; static DWORD iBytesWritten; bWriteRC = WriteFile(*hCom, &txchar, 1, &iBytesWritten,NULL); return; } int main() { HANDLE my=SerialInit("com1",1200); char letter; HANDLE *ptr; *ptr=my; SerialPutc(ptr,'a'); //letter=SerialGetc(ptr); getch(); return 0; }