Reputation: 40215
I want to read from COM1 at 115200,n,8,1 (preferably a blocking call, but I can add that. And I don't need threading).
The only code that I can find is on Stack Overflow in this question (Microsoft also had some useful info).
The author says that his code works, and I don't doubt him, but when I run the code I don't receive any characters, even though the port opened correctly (if I check with a terminal program, data are being sent).
Can someone please post a URL to some example C code? Thanks.
FWIW, here's my code:
// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
E_boolean OpenCom1(void)
{
COMMTIMEOUTS timeouts;
comPorthandle = CreateFile("COM1", // Specify port device: default "COM1"
GENERIC_READ | GENERIC_WRITE, // Specify mode that open device.
0, // the device isn't shared.
NULL, // the object gets a default security.
OPEN_EXISTING, // Specify which action to take on file.
0, // default (not overlapped i/o).
NULL); // default (hTemplate must be NULL for COM devices).
if (comPorthandle == INVALID_HANDLE_VALUE)
return False;
deviceControlBlock.DCBlength = sizeof(deviceControlBlock);
if((GetCommState(comPorthandle, &deviceControlBlock) == 0))
{
// CodeMe: do what?
return False;
}
deviceControlBlock.BaudRate = CBR_115200;
deviceControlBlock.StopBits = ONESTOPBIT;
deviceControlBlock.Parity = NOPARITY;
deviceControlBlock.ByteSize = DATABITS_8;
deviceControlBlock.fRtsControl = 0;
if (!SetCommState(comPorthandle, &deviceControlBlock))
{
// CodeMe: do what?
return False;
}
#if 0
// alternative to GetCommState() and SetCommState()
// both versions succeed
if (!BuildCommDCB("115200,n,8,1", &deviceControlBlock))
{
// CodeMe: do what?
return False;
}
#endif
// set short timeouts on the comm port.
timeouts.ReadIntervalTimeout = 0;
timeouts.ReadTotalTimeoutMultiplier = 1;
timeouts.ReadTotalTimeoutConstant = 1;
timeouts.WriteTotalTimeoutMultiplier = 1;
timeouts.WriteTotalTimeoutConstant = 1;
if (!SetCommTimeouts(comPorthandle, &timeouts))
{
// CodeMe: do what?
return False;
}
return True;
}//OpenCom1()
// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
void ReadCharacterFromCom1(INPUT char *theCharacter)
{
DWORD numBytesRead;
numBytesRead = 0;
while (numBytesRead == 0)
{
ReadFile(comPorthandle, // handle of file to read
theCharacter, // store read data here
sizeof(theCharacter), // number of bytes to read
&numBytesRead, // pointer to number of bytes actually read
NULL);
}
return;
}//ReadCharacterFromCom1()
Upvotes: 1
Views: 9698
Reputation: 43331
I see one problem in this code:
sizeof(theCharacter),
replace this with
sizeof(char),
because you want to read one byte, and sizeof(char*) is 4 or 8. Possibly there is something else, but you need to show more code.
Also, use Portmon program http://technet.microsoft.com/en-us/sysinternals/bb896644.aspx to see whether data is received - you can run it together with your program.
Upvotes: 2