Receipt printing via serial port (RS-232) - c++

Question

I'd like to write a c++ program(windows console application) to print receipts from a server (via websocket) to a locally connected(via rs-232) receipt printer(NCR 7197 rev 1.0).
I got both the websocket connection and the serial handle operating and ready.
My problem is, that I can't find any example to guide me through the process of printing, or how to even begin. I mean, do I have to write some bytes or read any before I start passing the "document" to the printer, or do I need to write any config bytes, or anything.
If someone has any suggestions to where to start, or any example preferably in c++, I will be thankful.

Answer 1

I came across the solution that I developed way back than, while cleaning my old projects folder. Seeing the multiple hundred of views on this question, I wanted to post an answer. Here is my solution, but it might be outdated:
The function to connect to a device through a COM port:
// Serial port connection handle connect method
HANDLE connect_h(wchar_t* s_port, int s_flowcontrol, int s_baudrate, int s_bytesize, int s_stopbits, int s_parity) {
wchar_t* port = s_port;
std::wstring ws(port);
std::string port_w(ws.begin(), ws.end());
// Open serial port
HANDLE hSerial;
hSerial = CreateFile(port, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if(hSerial == INVALID_HANDLE_VALUE) {
if(GetLastError() == ERROR_FILE_NOT_FOUND) {
// Serial port does not exist. Inform user.
std::cout << "Error: Serial port does not exists. Port: " << std::endl;
}
// Some other error occurred. Inform user.
std::cout << "Error: Cannot connect to port: " + port_w << std::endl;
std::cout << "Error code: " + GetLastError() << std::endl;
}
// Do some basic settings
DCB dcbSerialParams = { 0 };
dcbSerialParams.DCBlength = sizeof(dcbSerialParams);
if(!GetCommState(hSerial, &dcbSerialParams)) {
// Error getting state
std::cout << "Error: Cannot get port state. Port: " + port_w << std::endl;
std::cout << "Error code: " + GetLastError() << std::endl;
}
dcbSerialParams.BaudRate = s_baudrate;
dcbSerialParams.ByteSize = s_bytesize;
dcbSerialParams.StopBits = s_stopbits;
dcbSerialParams.Parity = s_parity;
// If flowcontrol set to XON/XOFF
if(s_flowcontrol == 1) {
dcbSerialParams.fDtrControl = DTR_CONTROL_DISABLE;
dcbSerialParams.fRtsControl = RTS_CONTROL_DISABLE;
dcbSerialParams.fOutX = true;
dcbSerialParams.fInX = true;
dcbSerialParams.XonChar = 0x11;
dcbSerialParams.XoffChar = 0x16;
}
if(!SetCommState(hSerial, &dcbSerialParams)) {
// error setting serial port state
std::cout << "Error: Cannot set port state. Port: " + port_w << std::endl;
std::cout << "Error code: " + GetLastError() << std::endl;
}
// Set timeouts
COMMTIMEOUTS timeouts = { 0 };
timeouts.ReadIntervalTimeout = 50;
timeouts.ReadTotalTimeoutConstant = 50;
timeouts.ReadTotalTimeoutMultiplier = 10;
timeouts.WriteTotalTimeoutConstant = 50;
timeouts.WriteTotalTimeoutMultiplier = 10;
if (!SetCommTimeouts(hSerial, &timeouts)) {
// Error occureed. Inform user
std::cout << "Error: Cannot set port timeouts. Port: " + port_w << std::endl;
std::cout << "Error code: " + GetLastError() << std::endl;
}
return hSerial;
}
Closing the serial port connection:
// Serial port connection handle close method
void close_h(const HANDLE &hSerial) {
CloseHandle(hSerial);
}
The function to print through the connected COM port:
// Printing recipe via serial port handle
std::string set_print(const HANDLE &hSerial, std::string &document) {
std::string result = "";
std::string printable = "";
// Format flags
bool _bold_flag = false;
bool _underline_flag = false;
bool _italic_flag = false;
// Process document for printing
for(int i = 0; i < (int)document.length(); ++i) {
if(document[i] == '\\') {
switch (document[i + 1]) {
// new line
case 'n':
printable.push_back((char)(0x0A));
i++;
break;
// underline format begin/end
case 'u':
if(!_underline_flag) {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x2D));
printable.push_back('1');
_underline_flag = true;
}
else {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x2D));
printable.push_back('0');
_underline_flag = false;
}
i++;
break;
// bold format begin/end
case 'b':
if (!_bold_flag) {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x47));
printable.push_back('1');
_bold_flag = true;
}
else {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x47));
printable.push_back('0');
_bold_flag = false;
}
i++;
break;
// italic format begin/end
case 'i':
if (!_italic_flag) {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x49));
printable.push_back('1');
_italic_flag = true;
}
else {
printable.push_back((char)(0x1B));
printable.push_back((char)(0x49));
printable.push_back('0');
_italic_flag = false;
}
i++;
break;
// if not recognized
default:
printable.push_back(document[i]);
break;
}
}
else {
printable.push_back(document[i]);
}
}
// Additional push
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
printable.push_back((char)(0x0A));
// Add EOF bytes
printable.push_back((char)(0x03));
printable.push_back((char)(0x04));
// Add knife cut command
printable.push_back((char)(0x19));
printable.push_back((char)(0x1B));
printable.push_back((char)(0x76));
// Convert to hexadecimal
int* hex_print = new int[printable.length()];
for(int i = 0; i < (int)printable.length(); ++i) {
hex_print[i] = (int)printable[i];
}
// Print
for(int i = 0; i < (int)printable.length(); ++i) {
int rq[1] = { hex_print[i] };
DWORD rqBytesWritten = 0;
if(!WriteFile(hSerial, rq, 1, &rqBytesWritten, NULL)) {
// error occurred. Report to user.
std::cout << "Error: Can't write byte. written: " + rqBytesWritten << std::endl;
}
}
// return status
return result;
}
And a test main function, to demonstrate the usage of these functions:
// MAIN()
int main(int argc, char* argv[]) {
// Create connection on COM port 1
HANDLE sh_printer = connect_h(L"COM1", 0, 38400);
// Print a string povided in first argument
set_print(sh_printer, args[1]);
// Close the COM port connection
close_h(sh_printer);
return 0;
}
I hope I could be of any help to anyone, who tires to use this ancient way of printing a receipt. :)