I have been struggling to translate this specific code, so it works on my Xcode program without the windows.h file. Does anybody have some ideas about how I can make it work?
Thank you in advance
This is the following code:
COMPort::COMPort ( const char * const portName )
: theDCB (NULL)
{
thePortHandle = (unsigned ) CreateFile ( portName
, GENERIC_READ | GENERIC_WRITE
, 0
, NULL
, OPEN_EXISTING
, FILE_FLAG_NO_BUFFERING
, NULL
);
if (thePortHandle == HFILE_ERROR)
{
throw runtime_error ("COMPort: failed to open.");
}
theDCB = new char [sizeof(DCB)];
getState();
setBlockingMode();
setHandshaking();
}
COMPort::~COMPort()
{
delete [] theDCB;
if (CloseHandle ((HANDLE)thePortHandle) == FALSE )
{
throw runtime_error ("COMPort: failed to close.");
}
}
It looks as if you are rewriting Windows code for serial communication. Windows and macOS are very different in this respect.
You will find many examples of how to do this, e.g.: https://www.pololu.com/docs/0J73/15.5
CreateFile translates to open
CloseHandle translates to close
The DCB struct translates to termios and is probably only needed temporarily for setting baud rate.
Most likely, your code also uses GetComm and SetComm. Those would translate to tcgetattr, tcsetattr and possibly cfsetispeed and cfsetospeed.
When it comes to concurrently writing to and reading from a serial port, macOS is much simpler than Windows where it is mutually exclusive unless non-blocking I/O is used. On macOS, reading and writing are independent.
If you also translate your code to Linux as well, you will find that macOS and Linux are almost the same.
Related
On linux, I am opening a pseudo tty on the master side. While there is no client on the slave side, the pseudo tty seems to be echoing everything I am writing to him, which is not what I am expecting.
Consider the folowing code :
int main(int argc, char * argv[])
{
int ptyfd;
int rc; /* return code */
char readbuf[3];
ptyfd = open("/dev/ptmx", O_RDWR | O_NOCTTY);
die_on_error(ptyfd, "open ptmx");
/* unlock and print slave name */
rc = unlockpt(ptyfd);
die_on_error(rc, "unlockpt");
printf("Slave pts name : %s\n", ptsname(ptyfd));
write(ptyfd, "C", 1);
rc=read(ptyfd, readbuf, 1);
die_on_error(rc, "read");
printf("read returned %c\n",readbuf[0]);
return 0;
}
When I run this program, I would expect the read call to block, but instead it immediately returns and the readbuf content is C. How can I change this behaviour ? When the slave side is not opened, I would like the character written on the master side to either vanish or be fifoed for later reading by the slave side.
Is changing the master side attributes the right way to do it ?
I thought the master side was not a tty, but apparently it is, so you can call things like tcgettattr and tcsetattr, and suppress the echo.
None of the older answers provided the correct C code, so here it is:
struct termios tmios;
tcgetattr(ptfd, &tmios);
tmios.c_lflag &= ~(ECHO);
tcsetattr(ptfd, TCSANOW, &tmios);
You can use the blocking getch() call. Also getch() will not echo the content.
I have a program that uses serial input. It's installed on quite a few machines with both Win7 and Win10. On some machines I have the strange issue that when opening the serial port at first it reads strange/incorrect values, mostly 0xff. When I close the port and reopen it, it works correctly.
m_port = new QSerialPort( info ); // some info from QSerialPortInfo::availablePorts();
if( m_port->open( QIODevice::ReadOnly ) )
{
m_port->setBaudRate( m_baudRate );
m_port->setDataBits( m_dataBits );
m_port->setParity( m_parity );
m_port->setStopBits( m_stopBits );
m_port->setFlowControl( QSerialPort::FlowControl::HardwareControl );
m_port->clear();
}
}
So am I just lucky that it works on like 90% of my installations and it's missing some explicit setting or might it be a bug in Qt? (5.6.0 msvc 2013)
Most likely what the problem here is that you're setting the settings on the serial port after you have opened it. Therefore, there's a small period of time where your settings could be in an odd state. It works the second time you open the port because the settings have been correctly set from the first time you opened the port.
QSerialPort will apply the serial port settings when open is called.
m_port = new QSerialPort( info ); // some info from QSerialPortInfo::availablePorts();
m_port->setBaudRate( m_baudRate );
m_port->setDataBits( m_dataBits );
m_port->setParity( m_parity );
m_port->setStopBits( m_stopBits );
m_port->setFlowControl( QSerialPort::FlowControl::HardwareControl );
if( m_port->open( QIODevice::ReadOnly ) )
{
m_port->clear();
}
We are using a usb-serial port converter to establish a serial port connection. We've tested it on a computer with no serial port and were able to initialize and send command through the converter to the device successfully. Once we release the .exe file to another PC with the same usb-serial converter, it fails to open com port.
The only thing we thought we need to change in the code is the port number, which we made sure were correct from device manager. COM6 on the working computer, and COM11 on the non-working one. We also tried to change COM11 to COM2 (an unused port number). The PC we try to make it work on does already have 3 real serial port (COM1, 3 and 4), but would they somehow be interfering this port?
We are using SerialCommHelper.cpp code to initialize the port.
HRESULT CSerialCommHelper:: Init(std::string szPortName, DWORD dwBaudRate,BYTE byParity,BYTE byStopBits,BYTE byByteSize)
{
HRESULT hr = S_OK;
try
{
m_hDataRx = CreateEvent(0,0,0,0);
//open the COM Port
//LPCWSTR _portName =LPCWSTR( szPortName.c_str());
wchar_t* wString=new wchar_t[4096];
MultiByteToWideChar(CP_ACP, 0, szPortName.c_str(), -1, wString, 4096);
m_hCommPort = ::CreateFile(wString,
GENERIC_READ|GENERIC_WRITE,//access ( read and write)
0, //(share) 0:cannot share the COM port
0, //security (None)
OPEN_EXISTING,// creation : open_existing
FILE_FLAG_OVERLAPPED,// we want overlapped operation
0// no templates file for COM port...
);
if ( m_hCommPort == INVALID_HANDLE_VALUE )
{
TRACE ( "CSerialCommHelper : Failed to open COM Port Reason: %d",GetLastError());
ASSERT ( 0 );
std::cout << "This is where the error happens" << std::endl;
return E_FAIL;
}
And we call this using
if( m_serial.Init(comPort, 38400, 0, 1, 8) != S_OK )
which comPort is set correctly, but Init never returns S_OK.
Any help is appreciated! Thank you!
The COM port name syntax changes for COM10 and higher. You need: "\\.\COM10"
as documented here...
http://support.microsoft.com/kb/115831/en-us
I am trying to open a com port for reading and writing using C++ but I can't seem to pass the first stage of actually opening it. I get an INVALID_HANDLE_VALUE on the handle
with GetLastError FILE_NOT_FOUND. I have searched around the web for a couple of days I'm fresh out of ideas. I have searched through all the questions regarding COM on this website too.
I have scanned through the existing ports (or so I believe) to get the name of the port right.
I also tried combinations of _T("COM1") with the slashes, without the slashes, with colon, without colon and without the _T
I'm using windows 7 on 64 bit machine.
this is the code i got
I'll be glad for any input on this
void SendToCom(char* data, int len)
{
DWORD cbNeeded = 0;
DWORD dwPorts = 0;
EnumPorts(NULL, 1, NULL, 0, &cbNeeded, &dwPorts);
//What will be the return value
BOOL bSuccess = FALSE;
LPCSTR COM1 ;
BYTE* pPorts = static_cast<BYTE*>(malloc(cbNeeded));
bSuccess = EnumPorts(NULL, 1, pPorts, cbNeeded, &cbNeeded, &dwPorts);
if (bSuccess){
PORT_INFO_1* pPortInfo = reinterpret_cast<PORT_INFO_1*>(pPorts);
for (DWORD i=0; i<dwPorts; i++)
{
//If it looks like "COMX" then
size_t nLen = _tcslen(pPortInfo->pName);
if (nLen > 3)
{
if ((_tcsnicmp(pPortInfo->pName, _T("COM"), 3) == 0) ){
COM1 =pPortInfo->pName;
//COM1 ="\\\\.\\COM1";
HANDLE m_hCommPort = CreateFile( COM1 ,
GENERIC_READ|GENERIC_WRITE, // access ( read and write)
0, // (share) 0:cannot share the COM port
NULL, // security (None)
OPEN_EXISTING, // creation : open_existing
FILE_FLAG_OVERLAPPED, // we want overlapped operation
NULL // no templates file for COM port...
);
if (m_hCommPort==INVALID_HANDLE_VALUE)
{
DWORD err = GetLastError();
if (err == ERROR_FILE_NOT_FOUND) {
MessageBox(hWnd,"ERROR_FILE_NOT_FOUND",NULL,MB_ABORTRETRYIGNORE);
}
else
if(err == ERROR_INVALID_NAME) {
MessageBox(hWnd,"ERROR_INVALID_NAME",NULL,MB_ABORTRETRYIGNORE);
}
else
{
MessageBox(hWnd,"unkown error",NULL,MB_ABORTRETRYIGNORE);
}
}
else{
WriteAndReadPort(m_hCommPort,data);
}
}
pPortInfo++;
}
}
}
}
The Solution is to use
The Problem is, if your port is Bigger then 9 then you have to use the Syntax
LPCWSTR szPortName = L"\\\\.\\COM11";.
If you are on Windows 10 - running all system updates might help !
I had the same issue that opening port "COM4" returned an error ERROR_FILE_NOT_FOUND. When running the program as "Administrator" it worked. Now after a updating to 1511 the program can open "COM4" even not running as "Administrator".
http://www.cplusplus.com/forum/windows/163855/
Use CreateFileA(...) instead of CreateFile(...)
ERROR_FILE_NOT_FOUND can be produced from CreateFile(L"\\\\.\\COM1", ...) and CreateFile(L"COM1:", ...) after using the Device Manager to change the assigned COM Port number. Disabling and re-enabling the device, or unplugging and reconnecting the USB adapter resolves the issue.
A useful test to confirm whether it is your program or the system is to send data to the port in command prompt. A successful test will show an empty line. A failed test will show an error message.
C:\drop>echo > \\.\COM1
The system cannot find the file specified.
C:\drop>echo > \\.\COM1
C:\drop>
Problem:
I have a hand held device that scans those graphic color barcodes on all packaging. There is a track device that I can use that will slide the device automatically. This track device functions by taking ascii code through a serial port. I need to get this thing to work in FileMaker on a Mac. So no terminal programs, etc...
What I've got so far:
I bought a Keyspan USB/Serial adapter. Using a program called ZTerm I was successful in sending commands to the device.
Example:
"C,7^M^J"
I was also able to do the same thing in Terminal using this command: screen /dev/tty.KeySerial1 57600
and then type in the same command above(but when I typed in I just hit Control-M and Control-J for the carriage return and line feed)
Now I'm writing a plug-in for FileMaker(in C++ of course). I want to get what I did above happen in C++ so when I install that plug-in in FileMaker I can just call one of those functions and have the whole process take place right there.
I'm able to connect to the device, but I can't talk to it. It is not responding to anything.
I've tried connecting to the device(successfully) using these:
FILE *comport;
if ((comport = fopen("/dev/tty.KeySerial1", "w")) == NULL){...}
and
int fd;
fd = open("/dev/tty.KeySerial1", O_RDWR | O_NOCTTY | O_NDELAY);
This is what I've tried so far in way of talking to the device:
fputs ("C,7^M^J",comport);
or
fprintf(comport,"C,7^M^J");
or
char buffer[] = { 'C' , ',' , '7' , '^' , 'M' , '^' , 'J' };
fwrite (buffer , 1 , sizeof(buffer) , comport );
or
fwrite('C,7^M^J', 1, 1, comport);
Questions:
When I connected to the device from Terminal and using ZTerm, I was able to set my baud rate of 57600. I think that may be why it isn't responding here. But I don't know how to do it here.... Does any one know how to do that? I tried this, but it didn't work:
comport->BaudRate = 57600;
There are a lot of class solutions out there but they all call these include files like termios.h and stdio.h. I don't have these and, for whatever reason, I can't find them to download. I've downloaded a few examples but there are like 20 files in them and they're all calling other files I can't find(like the ones listed above). Do I need to find these and if so where? I just don't know enough about C++ Is there a website where I can download libraries??
Another solution might be to put those terminal commands in C++. Is there a way to do that?
So this has been driving me crazy. I'm not a C++ guy, I only know basic programming concepts. Is anyone out there a C++ expert? I ideally I'd like this to just work using functions I already have, like those fwrite, fputs stuff.
Thanks!
Sending a ^ and then a M doesn't send control-M, thats just the way you write it,
to send a control character the easiest way is to just use the ascii control code.
ps. ^M is carriage return ie "\r" and ^J is linefeed "\n"
edit: Probably more than you will (hopefully) ever need to know - but read The Serial Port Howto before going any further.
This isn't a C++ question. You're asking how to interact with the TTY driver to set teh baud rate. The fact that you're opening the file under /dev tells me that you're on a unix derivative, so the relevant man page to read on a linux system is "man 3 termios".
Basically, you use the open() variant above, and pass the file descriptor to tcsetattr/tcgetattr.
Are you sure you've installed all the compiler tools properly? On my OS X 10.5.8 Mac,
termios.h and stdio.h are right there under /usr/include, just as I'd expect. The
code you've already found for serial port programming on other Unix variants should
only require minor changes (if any) to work on a Mac. Can you tell us a bit more about
what you've tried, and what went wrong?
mgb also has a good point about how the control characters need to be represented.
You can set the baud rate with ioctl. Here's a link to an example.
You don't specify which Unix you are using, so below I'm posting some Linux production code I use.
Pleae note below code is a class method so ignore any external (ie undeclared) references.
Steps are as follows -
Configure your termio structure, this is where you set any needed flags etc (ie the step you accomplished using zterm. The termio settings below configure the port to 8 databits, 1 stopbit and no parity (8-n-1). Also the port will be in "raw" (as opposed to cooked) mode so its a character stream, text isn't framed into lines etc The baud constants match the actual value, ie for 56700 baud you use "57600".
The timing parameters mean that characters are returned from the device as soon as they are available.
Once you have your termainal parameters set, you open the device (using POSIX open()), and then can use tcgetattr/tcsetattr to configure the device via the fd.
At this point you can read/write to the device using the read()/write() system calls.
Note that in the below example read() will block if no data is available so you may want to use select()/poll() if blocking is undesirable.
Hope that helps.
termios termio
tcflag_t baud_specifier;
//reset device state...
memset (&termio, 0, sizeof (termios));
read_buffer.clear();
//get our boad rate...
if (!(baud_specifier = baud_constant (baud))) {
ostringstream txt;
txt << "invalid baud - " << baud;
device_status_msg = txt.str();
status = false;
return (true);
}
//configure device state...
termio.c_cflag = baud_specifier | CS8 | CLOCAL | CREAD;
//do we want handshaking?
if (rtscts) {
termio.c_cflag |= CRTSCTS;
}
termio.c_iflag = IGNPAR;
termio.c_oflag = 0;
termio.c_lflag = 0;
//com port timing, no wait between characters and read unblocks as soon as there is a character
termio.c_cc[VTIME] = 0;
termio.c_cc[VMIN] = 0;
//open device...
if ((fd = open (device.c_str(), O_RDWR | O_NOCTTY)) == -1) {
ostringstream txt;
txt << "open(\"" << device << "\") failed with " << errno << " - "
<< std_error_msg (errno);
device_status_msg = txt.str();
status = false;
return (true);
}
//keep a copy of curret device state...
if (tcgetattr (fd, &old_termio) == -1) {
ostringstream txt;
txt << "tcgetattr() failed with " << errno << " - " << std_error_msg (errno);
device_status_msg = txt.str();
status = false;
return (true);
}
//flush any unwanted bytes
if (tcflush (fd, TCIOFLUSH) == -1) {
ostringstream txt;
txt << "tcflush() failed with " << errno << " - " << std_error_msg (errno);
device_status_msg = txt.str();
status = false;
return (true);
}
//apply our device config...
if (tcsetattr (fd, TCSANOW, &termio) == -1) {
ostringstream txt;
txt << "tcsetattr() failed with " << errno << " - " << std_error_msg (errno);
device_status_msg = txt.str();
status = false;
return (true);
}
node_log_f ("successfully initialised device %s at %i baud", "open_device()",
device.c_str(), baud);
status = true;
return (true);
}