Zeroes after each value that has been sent over serial communication - c++

I try to learn C++ by doing everything on it. However, I stuck while establishing serial communication over C++. I send an integer array over MCU(microcontroller) to the VS C++. I have no any software problem on the MCU side(I have tested). Additionally I can read char values correctly. However, when I read values by C++ I get 0 after each integer I read. I couldn't solve the problem, while I think that 0 corresponds to the newline.
For example if I send (5, 10, 15), I read (5, 0, 10, 0, 15, 0).
Can you help me in order to solve the problem? I am using Windows Api for serial communication.
The relevant code:
char ReadData; //temperory Character
int SerialBuffer[64] = { 0 }; //Buffer to send and receive data
.
.
.
do
{
Status = ReadFile(hComm, &ReadData, sizeof(ReadData), &NoBytesRead, NULL);
SerialBuffer[loop] = ReadData;
++loop;
} while (NoBytesRead > 0);
The whole code:
int main(void)
{
HANDLE hComm; // Handle to the Serial port
BOOL Status; // Status
DCB dcbSerialParams = { 0 }; // Initializing DCB structure
COMMTIMEOUTS timeouts = { 0 }; //Initializing timeouts structure
int SerialBuffer[64] = { 0 }; //Buffer to send and receive data
DWORD BytesWritten = 0; // No of bytes written to the port
DWORD dwEventMask; // Event mask to trigger
char ReadData; //temperory Character
DWORD NoBytesRead; // Bytes read by ReadFile()
unsigned char loop = 0;
wchar_t pszPortName[10] = { 0 }; //com port id
wchar_t PortNo[20] = { 0 }; //contain friendly name
hComm = CreateFile("\\\\.\\COM6", //friendly name
GENERIC_READ | GENERIC_WRITE, // Read/Write Access
0, // No Sharing, ports cant be shared
NULL, // No Security
OPEN_EXISTING, // Open existing port only
0, // Non Overlapped I/O
NULL); // Null for Comm Devices
if (hComm == INVALID_HANDLE_VALUE)
{
printf_s("\n Port can't be opened\n\n");
}
//Setting the Parameters for the SerialPort
dcbSerialParams.DCBlength = sizeof(dcbSerialParams);
Status = GetCommState(hComm, &dcbSerialParams); //retreives the current settings
if (Status == FALSE)
{
printf_s("\nError to Get the Com state\n\n");
}
dcbSerialParams.BaudRate = CBR_115200; //BaudRate = 9600
dcbSerialParams.ByteSize = 8; //ByteSize = 8
dcbSerialParams.StopBits = ONESTOPBIT; //StopBits = 1
dcbSerialParams.Parity = NOPARITY; //Parity = None
Status = SetCommState(hComm, &dcbSerialParams);
if (Status == FALSE)
{
printf_s("\nError to Setting DCB Structure\n\n");
}
//Setting Timeouts
timeouts.ReadIntervalTimeout = 50;
timeouts.ReadTotalTimeoutConstant = 50;
timeouts.ReadTotalTimeoutMultiplier = 10;
timeouts.WriteTotalTimeoutConstant = 50;
timeouts.WriteTotalTimeoutMultiplier = 10;
if (SetCommTimeouts(hComm, &timeouts) == FALSE)
{
printf_s("\nError to Setting Time outs");
}
Status = SetCommMask(hComm, EV_RXCHAR);
if (Status == FALSE)
{
printf_s("\nError to in Setting CommMask\n\n");
}
//Setting WaitComm() Event
Status = WaitCommEvent(hComm, &dwEventMask, NULL); //Wait for the character to be received
if (Status == FALSE)
{
printf_s("\nError! in Setting WaitCommEvent()\n\n");
}
//Read data and store in a buffer
do
{
Status = ReadFile(hComm, &ReadData, sizeof(ReadData), &NoBytesRead, NULL);
SerialBuffer[loop] = ReadData;
++loop;
} while (NoBytesRead > 0);
--loop; //Get Actual length of received data
printf_s("\nNumber of bytes received = %d\n\n", loop);
//print receive data on console
printf_s("\n\n");
int index = 0;
for (index = 0; index < loop; ++index)
{
printf_s("%d ", SerialBuffer[index]);
}
printf_s("\n\n");
CloseHandle(hComm);//Closing the Serial Port
return 0;
}

Related

WriteFile to Serial port in Windows waits a long time

I am writing a little serial bus (RS485) monitor in c++. It should read small data packages up to 32 bytes from the serialport an occasionally writes such a databus to the serial port when the user requests it.
Reading works perfectly. I set up a thread for reading using the SetCommMask(hComm, EV_RXCHAR); during initialization and later ReadFile(hComm, RS485PacketBuffer, sizeof(T_PACKET), &nBytes, NULL) to receive the package using timeouts for getting the inter package gaps.
In the main program I use a simple WriteFile(hComm, packet, packet->length + 5, &nBytes, NULL) to write the package.
This WriteFile seems to hang until there are some bytes received from the bus. Only then the package is sent and the bus devices recognize it and answer properly. Why does WriteFile wait for character receiving?
This is my init and thread code
HANDLE uart_init(char *portname, int baudrate)
{
HANDLE hComm;
BOOL Write_Status, Read_Status;
DCB dcbSerialParams;
COMMTIMEOUTS timeouts = { 0 };
hComm = CreateFile(L"com8", //port name
GENERIC_READ | GENERIC_WRITE, //Read/Write
0, // No Sharing
NULL, // No Security
OPEN_EXISTING, // Open existing port only
0, // Non Overlapped I/O
NULL); // Null for Comm Devices
if (hComm == INVALID_HANDLE_VALUE)
printf("Error in opening serial port\n");
else
printf("opening serial port successful\n");
Write_Status = GetCommState(hComm, &dcbSerialParams); //retreives the current settings
if (Write_Status == FALSE)
{
printf(" Error in GetCommState()\n");
CloseHandle(hComm);
return NULL;
}
dcbSerialParams.BaudRate = baudrate; // Setting BaudRate = 1200
dcbSerialParams.ByteSize = 8; // Setting ByteSize = 8
dcbSerialParams.StopBits = ONESTOPBIT; // Setting StopBits = 1
dcbSerialParams.Parity = NOPARITY; // Setting Parity = None
Write_Status = SetCommState(hComm, &dcbSerialParams); //Configuring the port according to settings in DCB
if (Write_Status == FALSE)
{
printf(" Error! in Setting DCB Structure\n");
CloseHandle(hComm);
return NULL;
}
else
{
printf(" Setting DCB Structure Successful\n");
printf(" Baudrate = %d\n", dcbSerialParams.BaudRate);
printf(" ByteSize = %d\n", dcbSerialParams.ByteSize);
printf(" StopBits = %d\n", dcbSerialParams.StopBits);
printf(" Parity = %d\n\n", dcbSerialParams.Parity);
}
// Set COM port timeout settings
timeouts.ReadIntervalTimeout = 50;
timeouts.ReadTotalTimeoutConstant = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 0;
timeouts.WriteTotalTimeoutMultiplier = 0;
if (SetCommTimeouts(hComm, &timeouts) == 0)
{
printf("Error setting timeouts\n");
CloseHandle(hComm);
return NULL;
}
Read_Status = SetCommMask(hComm, EV_RXCHAR); //Configure Windows to Monitor the serial device for Character Reception
if (Read_Status == FALSE)
printf(" Error! in Setting CommMask\n\n");
else
printf(" Setting CommMask successfull\n\n");
return hComm;
}
unsigned int __stdcall RS485Receiver(void* data)
{
BOOL status = 0;
DWORD dwEventMask = 0;
DWORD nBytes; // Bytes read by ReadFile()
puts("Serial Thread started");
if (hComm = uart_init("COM8", 1200))
{
printf("Waiting for Data Reception...\n");
status = WaitCommEvent(hComm, &dwEventMask, NULL); //Wait for the character to be received
if (status == FALSE)
{
printf("Error! in Setting WaitCommEvent()\n");
}
else //If WaitCommEvent()==True Read the RXed data using ReadFile();
{
_putch('.'); fflush(stdout);
do
{
//Read_Status = ReadFile(hComm, &TempChar, sizeof(TempChar), &NoBytesRead, NULL);
if ((!ReadFile(hComm, RS485PacketBuffer, sizeof(T_PACKET), &nBytes, NULL)))
{
printf("wrong character");
}
else if (nBytes)
{
RS485PrintPacket(RS485PacketBuffer, RS485PacketBuffer->length + 4, stdout);
}
} while (1);
}
CloseHandle(hComm);//Closing the Serial Port
}
puts("Serial Thread stopped");
return 0;
}
#endif
And this is the write function, which hangs until character receiving:
uint8_t sendPacket(T_PACKET* packet)
{
DWORD nBytes;
//calculate checksum
packet->d[packet->length] = crc8((uint8_t*)packet, packet->length + 4);
// PORTB &= ~(1 << TRANSENABLE); // ToDo: How do I enable transmitter on PC
Sleep(10); // short pause to stabilize bus transceiver
printf("Sende Paket, length = %u\n", packet->length+5);
if (!WriteFile(hComm, packet, packet->length + 5, &nBytes, NULL))
{
printf("Error writing text to RS485 port\n");
return 6;
}
printf("gesendet\n"); fflush(stdout);
if (nBytes != packet->length + 5) return 7;
printf("kein Fehler\n");
// PORTB |= (1 << TRANSENABLE); // ToDo: How do I disable transmitter on PC
return 0;`
}
I already tried several timout settings. These seems to have no effect to the problem. Maybe it is an issue with the USB/RS485 converter. I think as the RS485 is a bus, the serial port will probably see it's own send bytes. Maybe that causes the problem.
Or maybe the blocking receiver thread which is waiting for characters blocks the whole serial port.
As #Codo mentioned, I tried now to use overlapped IO. I have a complete solution now. See the answer below.
thanks for all the hints. #Codo's first remark was the solution. I have to use overlapping because Windows blocks also the sender when the receiver is waiting. Stupid, but true.
Since overlapping IO is a bit complicated I post my solution her for reference. Now I have to try the same in C#. :-)
HANDLE uart_init(char *portname, int baudrate)
{
HANDLE hComm;
BOOL Result;
DCB dcbSerialParams;
COMMTIMEOUTS timeouts = { 0 };
wchar_t wstr[50];
MultiByteToWideChar(CP_UTF8, 0, portname, -1, wstr, 50);
hComm = CreateFile(wstr, //port name
GENERIC_READ | GENERIC_WRITE, //Read/Write
0, // No Sharing
NULL, // No Security
OPEN_EXISTING, // Open existing port only
FILE_FLAG_OVERLAPPED, // Non Overlapped I/O
NULL); // Null for Comm Devices
if (hComm == INVALID_HANDLE_VALUE)
printf("Error in opening serial port\n");
else
printf("opening serial port successful\n");
Result = GetCommState(hComm, &dcbSerialParams); //retreives the current settings
if (Result == FALSE)
{
printf(" Error in GetCommState()\n");
CloseHandle(hComm);
return NULL;
}
dcbSerialParams.BaudRate = baudrate; // Setting BaudRate = 1200
dcbSerialParams.ByteSize = 8; // Setting ByteSize = 8
dcbSerialParams.StopBits = ONESTOPBIT; // Setting StopBits = 1
dcbSerialParams.Parity = NOPARITY; // Setting Parity = None
dcbSerialParams.fBinary = TRUE; // has to be TRUE in Windows
dcbSerialParams.fParity = FALSE; // No parity
dcbSerialParams.fOutxCtsFlow = FALSE; // No CTS flow control
dcbSerialParams.fOutxDsrFlow = FALSE; // No DSR flow control
dcbSerialParams.fDtrControl = FALSE; // No DTR low control
dcbSerialParams.fDsrSensitivity = FALSE; // Ignore DSR
dcbSerialParams.fOutX = FALSE; // No XON/XOFF flow control
dcbSerialParams.fInX = FALSE; // No XON/XOFF flow control
dcbSerialParams.fErrorChar = FALSE; // do not replace errors
dcbSerialParams.fNull = FALSE; // allow NULL bytes
dcbSerialParams.fRtsControl = RTS_CONTROL_ENABLE; // Enable RTS pin
dcbSerialParams.fAbortOnError = FALSE; // do not stop on error
Result = SetCommState(hComm, &dcbSerialParams); //Configuring the port according to settings in DCB
if (Result == FALSE)
{
printf(" Error! in Setting DCB Structure\n");
CloseHandle(hComm);
return NULL;
}
else
{
printf(" Setting DCB Structure Successful\n");
printf(" Baudrate = %d\n", dcbSerialParams.BaudRate);
printf(" ByteSize = %d\n", dcbSerialParams.ByteSize);
printf(" StopBits = %d\n", dcbSerialParams.StopBits);
printf(" Parity = %d\n\n", dcbSerialParams.Parity);
}
// Set COM port timeout settings
timeouts.ReadIntervalTimeout = 50;
timeouts.ReadTotalTimeoutConstant = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 0;
timeouts.WriteTotalTimeoutMultiplier = 0;
if (SetCommTimeouts(hComm, &timeouts) == 0)
{
printf("Error setting timeouts\n");
CloseHandle(hComm);
return NULL;
}
Result = SetCommMask(hComm, EV_RXCHAR); //Configure Windows to Monitor the serial device for Character Reception
if (Result == FALSE)
printf(" Error in Setting CommMask\n\n");
else
printf(" Setting CommMask successfull\n\n");
return hComm;
}
unsigned int __stdcall RS485Receiver(void* data)
{
BOOL status = 0;
DWORD dwEventMask = 0;
DWORD nBytes; // Bytes read by ReadFile()
DWORD dwRes;
DWORD dwRead;
BOOL fWaitingOnRead = FALSE;
OVERLAPPED osRead = { 0 };
puts("Serial Thread started");
if (hComm = uart_init((char *)data, 1200))
{
printf("Waiting for Data Reception...\n");
// Create the overlapped event. Must be closed before exiting
// to avoid a handle leak.
osRead.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (osRead.hEvent == NULL)
{
CloseHandle(hComm);//Closing the Serial Port
puts("Serial Thread stopped");
return 0;
}
while (1)
{
if (!fWaitingOnRead)
{
// Issue read operation.
if (!ReadFile(hComm, RS485PacketBuffer, sizeof(T_PACKET), &dwRead, &osRead))
{
if (GetLastError() != ERROR_IO_PENDING) // read not delayed?
printf("wrong character");
else
fWaitingOnRead = TRUE;
}
else {
// read completed immediately
RS485PrintPacket(RS485PacketBuffer, RS485PacketBuffer->length + 4, stdout);
}
}
if (fWaitingOnRead)
{
dwRes = WaitForSingleObject(osRead.hEvent, INFINITE);
switch (dwRes)
{
// Read completed.
case WAIT_OBJECT_0:
if (!GetOverlappedResult(hComm, &osRead, &dwRead, FALSE))
printf("wrong character");
else
// Read completed successfully.
RS485PrintPacket(RS485PacketBuffer, RS485PacketBuffer->length + 4, stdout);
// Reset flag so that another opertion can be issued.
fWaitingOnRead = FALSE;
break;
case WAIT_TIMEOUT:
// Operation isn't complete yet. fWaitingOnRead flag isn't
// changed since I'll loop back around, and I don't want
// to issue another read until the first one finishes.
//
// This is a good time to do some background work.
break;
default:
// Error in the WaitForSingleObject; abort.
// This indicates a problem with the OVERLAPPED structure's
// event handle.
break;
}
}
}
CloseHandle(hComm); //Closing the Serial Port
}
puts("Serial Thread stopped");
return 0;
}
/*
* Send a data packet
* use this only for Windows
*/
uint8_t sendPacket(T_PACKET* packet)
{
DWORD nBytes;
uint8_t fRes = 0;
OVERLAPPED osWrite = { 0 };
//calculate checksum
packet->d[packet->length] = crc8((uint8_t*)packet, packet->length + 4);
// PORTB &= ~(1 << TRANSENABLE); // ToDo: How do I enable transmitter on PC
Sleep(10); // short pause to stabilize bus transceiver
osWrite.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (osWrite.hEvent == NULL)
// error creating overlapped event handle
return ERR_COMM_WR;
if (!WriteFile(hComm, packet, packet->length + 5, &nBytes, &osWrite))
{
if (GetLastError() != ERROR_IO_PENDING) // read not delayed?
{
fRes = ERR_COMM_WR;
}
else
{
if (!GetOverlappedResult(hComm, &osWrite, &nBytes, TRUE))
{
fRes = ERR_COMM_WR;
}
else
{
// Read completed successfully.
RS485PrintPacket(packet, packet->length + 4, stdout);
}
}
}
CloseHandle(osWrite.hEvent);
// PORTB |= (1 << TRANSENABLE); // ToDo: How do I disable transmitter on PC
return fRes;
}

Why is my serial read application not responding?

I have written the following serial read function that is supposed to wait for the EV_RXCHAR event to be raised, after which it should read in a continuous loop
void CGCUGUIDlg::OnStartcom()
{
m_hComm = ::CreateFile(Com, //String that contains COM port name
GENERIC_READ|GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
0
);
fnCommState();
DCB dcb = {0};
dcb.DCBlength = sizeof(dcb);
Status = GetCommState(m_hComm, &dcb);
dcb.BaudRate = CBR_115200;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY;
SetCommState(m_hComm, &dcb);
OVERLAPPED o;
BOOL fSuccess;
DWORD dwEvtMask;
DWORD NoBytesRead;
BYTE abBuffer[100];
fSuccess = SetCommMask(m_hComm,EV_RXCHAR);
if(!fSuccess)
{
MessageBox("SetCommMask failed with error %s",LPCTSTR(GetLastError()));
return;
}
o.hEvent = CreateFile(0,0,0,NULL,TRUE,FALSE,NULL);
o.Internal = 0;
o.InternalHigh = 0;
o.Offset = 0;
o.OffsetHigh = 0;
assert(o.hEvent);
for(;;)
{
if(WaitCommEvent(m_hComm,&dwEvtMask,&o)) //if 1
{
if(dwEvtMask & EV_RXCHAR) //if 2
{
do
{
ReadFile(m_hComm,&abBuffer,sizeof(abBuffer),&NoBytesRead,&o);
data.Append(LPCTSTR(abBuffer),NoBytesRead);
}//do
while(NoBytesRead>0);
if((data.GetAt(1)==10)&& data.GetLength() == 100) //if 3, EDIT 1
{
result = data;
this->SetDlgItemText(IDC_RXRAW,LPCTSTR(result));
this->UpdateDate(false); //EDIT 2
}//if 3
}//if 2
}//if 1
Sleep(40);
}//for
}
SOME DETAILS:
1 The application receives 100 bytes every 60 milliseconds, with no gap between bytes in those 100 bytes.
2 The header bytes are specified so I am doing a check for this and the message size.
3 Both data and result are CString variables.
4 Although I did not copy the code outright, I did base my code heavily on the monitoring code given here. This is why I am using an Overlapped method, even though I am only reading data.
The code compiles fine (big whoop, I know) but on running the application hangs when the function is called. I am using this emulator to send data.
Could someone point out the errors in my work?
UPDATE:
I tried to isolate the cause of my problem, so I tried to check if the EV_RXCHAR event was being called. I ran the following heavily shortened code:
for(;;)
{
if(WaitCommEvent(m_hComm,&dwEvtMask,0)) //if 1
{
if(dwEvtMask & EV_RXCHAR) //if 2
{
MessageBox("Data");
break;
}
break;
}
else
MessageBox("No Data");
break;
}//for
I am receiving the data, my code to handle the data is horrible. I am starting to work on this.
UPDATE 2: Still working on it, any input would be highly appreciated.

COMMTIMEOUT and Thread not timming out on serial port Read function

I am calling a function that operates an I/o board through a serial port to check that it is communicating in an instance of my main class.
I know that this is risky but unfortunately this is an old section of code that has been used for a while so I am unable to alter the functionality while I have been asked to improve it.
If there is no communication issue the application will start up, use the function and continue with no issue.
The problem arises when there is a communication fault with the I/o board, I have found that the read function is hanging and stopping the app from starting for the majority of the time. On occasion the app will load and will report that there is a communication fault.
What I am trying to achieve is for the application to load successfully every time when there is a communication fault.
The comport is set up with COMMTIMEOUTs originally which I expected would timeout the port when there has been nothing to read. I have attempted to alter the timings but with no avail.
I have also attempted to use a thread for the read function so that it would not block the start up but still it hangs.
Currently the port is set up synchronously.
Has anybody got any suggestions? I can put some code examples up if required.
Main.cpp
extern COMPort comPort;
BOOL Main::InitInstance()
{
int i = comPort.DoorLatchOff();
If(i<0) printf("Error checksum. COM port?\n");
else printf("checksum ok.\n");
}
COMPort.h
class CCOMPort
{
public:
CCOMPort (COM_PORT port = NULL_COM, DCB * state = NULL);
BOOL SetPortNumber (COM_PORT port = NULL_COM, DCB * state = NULL);
void Read(BYTE* buff, int count);
int DoorLatchOff(void);
protected:
HANDLE m_hPort;
};
static HANDLE m_hPortThreaded;
typedef struct readParam{BYTE* readBuff;int readCount;}RP, *PRP;
DWORD WINAPI ThreadedRead( LPVOID lpParam );
COMPort.cpp
CCOMPort::CCOMPort (COM_PORT port, DCB * state) : m_portNum (port), m_hPort(INVALID_HANDLE_VALUE)
{
SetPortNumber (port, state);
}
BOOL CCOMPort::SetPortNumber (COM_PORT port, DCB * state)
{
if (m_hPort != INVALID_HANDLE_VALUE){
::CloseHandle (m_hPort);
m_hPort = INVALID_HANDLE_VALUE;
}
m_portNum = port;
m_currState = m_defState;
m_originState = m_defState;
if (m_portNum != NULL_COM){
stringstream ssPortName;
ssPortName << "COM" << (m_portNum + 1) << ":" << flush;
m_hPort = ::CreateFile (ssPortName.str().c_str(),
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_WRITE_THROUGH,
NULL);
if (m_hPort == INVALID_HANDLE_VALUE)
return FALSE;
else
{
GetState (& m_originState);
if (state)
m_currState = * state;
SetState (& m_currState);
GetCommTimeouts(m_hPort, &timeouts);
timeouts.ReadIntervalTimeout = 75; //15
timeouts.ReadTotalTimeoutMultiplier = 5; //1
timeouts.ReadTotalTimeoutConstant = 1250; //250
timeouts.WriteTotalTimeoutMultiplier = 5; //1
timeouts.WriteTotalTimeoutConstant = 1250; //250
SetCommTimeouts(m_hPort, &timeouts);
FlushOutput ();
FlushInput ();
PurgeOutput ();
PurgeInput ();
}
}
return TRUE;
}
void CCOMPort::Read(BYTE* buff, int count)
{
PRP pReadArray[1];
DWORD dwThreadArray[1];
HANDLE hThreadArray[1];
m_hPortThreaded = m_hPort;
pReadArray[0] = (PRP) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(RP));
if(pReadArray[0] == NULL){
ExitProcess(2);
}
pReadArray[0]->readBuff = buff;
pReadArray[0]->readCount = count;
hThreadArray[0] = CreateThread(NULL,
0,
ThreadedRead,
pReadArray[0],
0,
&dwThreadArray[0]);
if(hThreadArray[0] == NULL){
ExitProcess(3);
}
WaitForSingleObject(hThreadArray[0],500/*INFINITE*/);
CloseHandle(hThreadArray[0]);
if(pReadArray[0] != NULL){
HeapFree(GetProcessHeap(), 0, pReadArray[0]);
pReadArray[0] = NULL;
}
}
DWORD WINAPI ThreadedRead(LPVOID lpParam)
{
BOOL bDone = FALSE, bResult;
//int buff_idx = 0;
DWORD dwCommModemStatus;
DWORD dwBytesTransfered;
PRP pReadArray;
pReadArray = (PRP)lpParam;
SetCommMask(m_hPortThreaded, EV_RXCHAR);
while(!bDone){
WaitCommEvent(m_hPortThreaded, &dwCommModemStatus, 0);
if(dwCommModemStatus == 0){
bDone = TRUE;
break;
}
if(dwCommModemStatus & EV_RXCHAR){
bResult = ReadFile(m_hPortThreaded, pReadArray[0].readBuff, pReadArray[0].readCount, &dwBytesTransfered, 0);
bDone = TRUE;
}
}
return(bResult);
}
int COMPort::DoorLatchOff(void)
{
unsigned char comm_str[10];
int chksum, chksum1;
DWORD count = 6;
WriteComm(21, 7, 0);
comm.Read(comm_str, count);
chksum = comm_str[0] + comm_str[2] + comm_str[3];
chksum1 = comm_str[4];
chksum1 = (chksum1 << 8) | comm_str[5];
if(chksum == chksum1)
return(0);
else
return(-1);
}
Recently I stuck at the same problem, but I have solved it.
There are two ways:
On forums some people recomend to set both ReadIntervalTimeout and ReadTotalTimeoutMultiplier to MAXDWORD, as recomened in MSDN documentation in the REMARKS section. But in this case the funtion returns each time when there is at least one character in the input buffer.
The most robust decision I have found is just to set ReadIntervalTimeout and ReadTotalTimeoutMultiplier to 0, and ReadTotalTimeoutConstant to your timeout value, as below. It works pretty fine for me.
COMMTIMEOUTS commtimeouts;
GetCommTimeouts (hCommFile, &commtimeouts);
commtimeouts.ReadIntervalTimeout = 0;
commtimeouts.ReadTotalTimeoutMultiplier = 0;
commtimeouts.ReadTotalTimeoutConstant = timeout;
commtimeouts.WriteTotalTimeoutMultiplier = 0;
commtimeouts.WriteTotalTimeoutConstant = 0;
SetCommTimeouts (hCommFile, &commtimeouts);
Please, could you try to remove the WaitCommEvent function from ThreadedRead and see if it still hangs?
DWORD WINAPI ThreadedRead(LPVOID lpParam)
{
BOOL bResult;
DWORD dwBytesTransfered = 0;
PRP pReadArray;
pReadArray = (PRP)lpParam;
while (dwBytesTransfered == 0) {
bResult = ReadFile(m_hPortThreaded, pReadArray[0].readBuff, pReadArray[0].readCount, &dwBytesTransfered, 0);
Sleep(250);
}
return(bResult);
}
When dealing with hw I/O it is a best practice to decouple the Application (GUI) thread from the command-execution thread.
If you are developing a C++ Win32 app you could use SerialLib. It is an old but stable Win32 event-driven serial library.

correctly reading or writing serial port Windows API

I have read alot of issues with serial port reading and writing. None so far have helped me figure out what my code is missing. The msdn example for c++ has undefined variables and missing brackets so although i can add brackets it still does not function. Here's what I've got at this point. It appears I can open the port and do the configuration but I cannot read a byte/char of data. I really just want a simple asyncronous serial read/write for aprogram to read from an Arduino.
class MY_SERIAL
{
HANDLE serialinstance;
DWORD dwStoredFlags;
DWORD dwRes;
DWORD dwCommEvent;
OVERLAPPED osStatus = {0};
BOOL fWaitingOnStat;
//dwStoredFlags = EV_BREAK | EV_CTS | EV_DSR | EV_ERR | EV_RING | EV_RLSD | EV_RXCHAR | EV_RXFLAG | EV_TXEMPTY ;
DCB dcb;
COMMTIMEOUTS timeouts;
COMMCONFIG serialconfig;
public:
char inBuffer[1000];
char outBuffer[100];
PDWORD noBytes;
void close_serial()
{
CloseHandle(serialinstance);
}
//----------------------------------------------------
bool open_serial(LPCSTR portNumber) // serial port name use this format "\\\\.\\COM10"
{
serialinstance = CreateFile(portNumber, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
if(serialinstance == INVALID_HANDLE_VALUE)
{
int error = GetLastError();
printf("ERROR opening serial port %s\r\n", portNumber);
if(error == 0x2){printf("ERROR_FILE_NOT_FOUND\r\n");}
if(error == 0x5){printf("ERROR_ACCESS_DENIED\r\n");}
if(error == 0xC){printf("ERROR_INVALID_ACCESS\r\n");}
if(error == 0x6){printf("ERROR_INVALID_HANDLE\r\n");}
printf("error code %d\r\n", error);
return false;
}
if(GetCommState(serialinstance, &dcb)!= true)
{
printf("ERROR getting current state of COM %d \r\n", GetLastError());
return false;
}
else{printf("debug read current comstate\r\n");}
FillMemory(&dcb, sizeof(dcb), 0); //zero initialize the structure
dcb.DCBlength = sizeof(dcb); //fill in length
dcb.BaudRate = CBR_115200; // baud rate
dcb.ByteSize = 8; // data size, xmit and rcv
dcb.Parity = NOPARITY; // parity bit
dcb.StopBits = ONESTOPBIT;
if(SetCommState(serialinstance, &dcb) != true)
{
printf("ERROR setting new state of COM %d \r\n", GetLastError());
return false;
}
else{printf("debug set new comstate\r\n");}
/*
if (!BuildCommDCB("115200,n,8,1", &dcb)) //fills in basic async details
{
printf("ERROR getting port comstate\r\n");
return FALSE;
}
*/
if (!SetCommMask(serialinstance, EV_RXCHAR))
{
printf("ERROR setting new COM MASK %d \r\n", GetLastError());
return false;
}
else{printf("debug commmask set\r\n");}
timeouts.ReadIntervalTimeout = MAXDWORD;
timeouts.ReadTotalTimeoutMultiplier = 20;
timeouts.ReadTotalTimeoutConstant = 0;
timeouts.WriteTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 0;
if (!SetCommTimeouts(serialinstance, &timeouts))
{
printf("ERROR setting timeout parameters\r\n");
return false;
}
else{printf("debug timeouts set\r\n");}
osStatus.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (osStatus.hEvent == NULL)
{// error creating event; abort
printf("ERROR creating Serial EVENT\r\n");
return false;
}
else{printf("debug event created set\r\n");}
osStatus.Internal = 0;
osStatus.InternalHigh = 0;
osStatus.Offset = 0;
osStatus.OffsetHigh = 0;
assert(osStatus.hEvent);
printf("debug com port setting complete\r\n");
return true;
}
//---------------------------------------------------------
bool read_serial_simple()
{
char m[1000];
LPDWORD bytesRead;
if (WaitCommEvent(serialinstance, &dwCommEvent, &osStatus))
{
if(dwCommEvent & EV_RXCHAR)
{
ReadFile(serialinstance, &m, 1, bytesRead, &osStatus);
printf("data read = %d, number bytes read = %d \r\n", m, bytesRead);
return true;
}
else
{
int error = GetLastError();
if(error == ERROR_IO_PENDING){printf(" waiting on incomplete IO\r\n");}
else{printf("ERROR %d\r\n", error);}
return false;
}
}
return false;
}
};
So I stripped the read function down. I now get a char and it reports reading 1 byte but the value of the char is incorrect. I get a series of 48, 13, 10, and occasionally a 50 value for the byte. However the Arduino is sending a series a 0's then a 128 as verified with TerraTerm. What else do I need here?
bool read_serial_simple()
{
unsigned char m = 0;
DWORD bytesRead;
if(ReadFile(serialinstance, &m, 1, &bytesRead, &osStatus) == true)
{
printf("data read = %d, number bytes read = %d \r\n", m, bytesRead);
return true;
}
else{
int error = GetLastError();
if(error == ERROR_IO_PENDING){printf(" waiting on incomplete IO\r\n");}
else{printf("ERROR %d\r\n", error);}
return false;
}
}
So now I can read a byte of data but I cannot write a byte or more to the port. I just get ERROR_IO_PENDING. Can someone help out with this as well. Write function of my class below.
bool write(DWORD noBytesToWrite)
{
if(WriteFile(serialinstance, outBuffer, noBytesToWrite, NULL, &osStatus) == true)
{
printf("message sent\r\n");
return true;
}
else
{
int error = GetLastError();
if(error != ERROR_IO_PENDING){LastError();}
return false;
}
}
I'm calling both functions from main as follows
myserial.open_serial(COM12);
myserial.outBuffer[0] = 'H';
myserial.outBuffer[1] = 'e';
myserial.outBuffer[2] = 'L';
myserial.outBuffer[3] = 'l';
myserial.outBuffer[4] = 'O';
for(int n=0; n<5; n++){printf("%c", myserial.outBuffer[n]);}
printf("\r\n");
while(1)
{
myserial.read();
myserial.write(5);
//system("PAUSE");
}
Currently the arduino is set up to read bytes in and repeat them back to the pc. It is doing this fine on the arduino IDE serial monitor so now I just need to get this pc program to write out.
Your bytesRead variable is an uninitialized pointer. You are passing an invalid address to ReadFile() to write to.
Replace LPDWORD bytesRead with DWORD bytesRead, then pass it to ReadFile() using &bytesRead.
Edit:
Also eliminate the FILE_FLAG_OVERLAPPED. You are not handling it properly, and there is no point in using it if you WaitForSingleObject() before reading.
Sorry my answer is a bit late, but as I was checking up on another serial port detail I found this.
There is a bit flaw in the original code. You are calling CreateFile with the FILE_FLAG_OVERLAPPED flag. This means you want to use non-blocking calls. You either need to remove this flag, or change your ReadFile and WriteFile calls so that they include a pointer to an OVERLAPPED structure WriteFile.
Your code works with ReadFile as it will complete syncrhronously as there is a character already waiting. The WriteFile will return IO_PENDING result to indicate that the write has been queued.

Serial Comm using WriteFile/ReadFile

//#include "StdAfx.h"
#include <stdio.h>
#include <windows.h>
#include <winbase.h>
#include <iostream>
#include <tchar.h>
using namespace std;
int main()
{
int com = 'COM2';
string data = "\n 010400 \n";
char output[32];
//unsigned int length = 0;
DCB config = {0};
bool abContinue = true;
DWORD dwBytesWritten;
DWORD dwBytesRead;
int isRead = false;
HANDLE m_hCommPort = ::CreateFile(L"COM2",
GENERIC_READ|GENERIC_WRITE,//access ( read and write)
0, //(share) 0:cannot share the COM port
0, //security (None)
OPEN_EXISTING,// creation : open_existing
0, // we dont want overlapped operation
0// no templates file for COM port...
);
config.DCBlength = sizeof(config);
if((GetCommState(m_hCommPort, &config) == 0))
{
printf("Get configuration port has a problem.");
return FALSE;
}
config.BaudRate = 9600;
config.StopBits = ONESTOPBIT;
config.Parity = PARITY_NONE;
config.ByteSize = DATABITS_8;
config.fDtrControl = 0;
config.fRtsControl = 0;
if (!SetCommState(m_hCommPort, &config))
{
printf( "Failed to Set Comm State Reason: %d\n",GetLastError());
//return E_FAIL;
}
printf("Current Settings\n Baud Rate %d\n Parity %d\n Byte Size %d\n Stop Bits %d", config.BaudRate,
config.Parity, config.ByteSize, config.StopBits);
int isWritten = WriteFile(m_hCommPort, &data,(DWORD) sizeof(data), &dwBytesWritten, NULL);
//memset(output, 0, sizeof(output));
while (abContinue)
{
isRead = ReadFile(m_hCommPort, output, sizeof(output), &dwBytesRead, NULL);
if(!isRead)
{
abContinue = false;
break;
}
}
cin.get();
}
I am having trouble reading from the com port. If I step through the code, it goes into "isRead = ReadFile(m_hCommPort, output, sizeof(output), &dwBytesRead, NULL);" and doesn't come back out.... This is my first try at this with no success.
You might try some code something like this after you've opened the file, but before you try to use it:
COMMTIMEOUTS timeouts;
timeouts.ReadIntervalTimeout = 1;
timeouts.ReadTotalTimeoutMultiplier = 1;
timeouts.ReadTotalTimeoutConstant = 1;
timeouts.WriteTotalTimeoutMultiplier = 1;
timeouts.WriteTotalTimeoutConstant = 1;
if (!SetCommTimeouts(m_hCommPort, &timeouts))
// setting timeouts failed.
Edit: perhaps it's easier to start with some code that works, and make it do what you want rather than trying to get your code to work. Here's a simple terminal program. It's minimalist in the extreme, but does work (at least well enough to let me see output from my GPS, for one example). It's a long ways from what anybody (least of all me) would call sophisticated, but should give at least some idea of how to get started.
#include <stdio.h>
#include <conio.h>
#include <string.h>
#define STRICT
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
void system_error(char *name) {
// Retrieve, format, and print out a message from the last error. The
// `name' that's passed should be in the form of a present tense noun
// (phrase) such as "opening file".
//
char *ptr = NULL;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM,
0,
GetLastError(),
0,
(char *)&ptr,
1024,
NULL);
fprintf(stderr, "\nError %s: %s\n", name, ptr);
LocalFree(ptr);
}
int main(int argc, char **argv) {
int ch;
char buffer[1];
HANDLE file;
COMMTIMEOUTS timeouts;
DWORD read, written;
DCB port;
HANDLE keyboard = GetStdHandle(STD_INPUT_HANDLE);
HANDLE screen = GetStdHandle(STD_OUTPUT_HANDLE);
DWORD mode;
char port_name[128] = "\\\\.\\COM3";
char init[] = ""; // e.g., "ATZ" to completely reset a modem.
if ( argc > 2 )
sprintf(port_name, "\\\\.\\COM%c", argv[1][0]);
// open the comm port.
file = CreateFile(port_name,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
0,
NULL);
if ( INVALID_HANDLE_VALUE == file) {
system_error("opening file");
return 1;
}
// get the current DCB, and adjust a few bits to our liking.
memset(&port, 0, sizeof(port));
port.DCBlength = sizeof(port);
if ( !GetCommState(file, &port))
system_error("getting comm state");
if (!BuildCommDCB("baud=19200 parity=n data=8 stop=1", &port))
system_error("building comm DCB");
if (!SetCommState(file, &port))
system_error("adjusting port settings");
// set short timeouts on the comm port.
timeouts.ReadIntervalTimeout = 1;
timeouts.ReadTotalTimeoutMultiplier = 1;
timeouts.ReadTotalTimeoutConstant = 1;
timeouts.WriteTotalTimeoutMultiplier = 1;
timeouts.WriteTotalTimeoutConstant = 1;
if (!SetCommTimeouts(file, &timeouts))
system_error("setting port time-outs.");
// set keyboard to raw reading.
if (!GetConsoleMode(keyboard, &mode))
system_error("getting keyboard mode");
mode &= ~ ENABLE_PROCESSED_INPUT;
if (!SetConsoleMode(keyboard, mode))
system_error("setting keyboard mode");
if (!EscapeCommFunction(file, CLRDTR))
system_error("clearing DTR");
Sleep(200);
if (!EscapeCommFunction(file, SETDTR))
system_error("setting DTR");
if ( !WriteFile(file, init, sizeof(init), &written, NULL))
system_error("writing data to port");
if (written != sizeof(init))
system_error("not all data written to port");
// basic terminal loop:
do {
// check for data on port and display it on screen.
ReadFile(file, buffer, sizeof(buffer), &read, NULL);
if ( read )
WriteFile(screen, buffer, read, &written, NULL);
// check for keypress, and write any out the port.
if ( kbhit() ) {
ch = getch();
WriteFile(file, &ch, 1, &written, NULL);
}
// until user hits ctrl-backspace.
} while ( ch != 127);
// close up and go home.
CloseHandle(keyboard);
CloseHandle(file);
return 0;
}
If you do not explicitly set the timeouts, then ReadFile will indefinitely block until data becomes available.
ReadFile function may be blocking your thread,if so, it will remain blocked until some data can be read from Serial port. Here is a link see if its help. Good luck.
I had this problem on a readfile, with the timeouts set. This was driving me crackers so I ended up getting some code from the web which did work and then changing line by line to see where the error was.
Turns out he readfile was fine. My problem was a WaitCommEvent which was hanging when the port was disconnected as no com event is ever received...