我正在為熱敏收據列印機擴展收據列印串行埠 (COM) 介面，以便在不需要虛擬串行埠的情況下使用 USB 介面。我有一個作業原型，它將列舉連接的 USB 設備，找到具有特定供應商 ID 和產品 ID 的設備的 USB 路徑，并使用CreateFile().
現有的串行埠代碼使用封裝在一組函式中的 Windows API。我采用的方法是使用相同的函式集添加額外的代碼，但這取決于 USB 連接而不是串行埠連接。我以前使用相同的方法允許通過串行埠或 WiFi/LAN 連接使用廚房列印機，并且成功地對現有代碼進行了最小的更改。
不幸的是，使用函式庫的現有代碼取決于使用ReadFile()指定超時的函式，這樣如果熱敏列印機在合理的時間內沒有回應狀態請求，應用程式可以將其標記為關閉并允許操作繼續或使用備份或輔助列印機。
如何指定使用 USB 路徑名打開與通信設備的連接ReadFile()的檔案句柄上的超時CreateFile()？
需要考慮的是，這是用于多個串行通信設備（收據列印機、廚房列印機、秤等）的多執行緒代碼，但是執行緒將獨占訪問特定設備（廚房列印功能打開廚房列印機的串行埠）僅，秤讀取功能僅打開串行埠以進行秤等）。
在現有的串行埠代碼中，用于設定超時的函式SetCommTimeouts()，用于打開的串行埠連接CreateFile()不適用于打開的 USB 連接CreateFile()（請參閱SetupComm, SetCommState, SetCommTimeouts fail with USB device）。這意味著需要一些其他機制來提供一種方法來允許由于使用 USB 設備路徑名時超時而導致的 I/O 故障。
我們使用以下代碼段來打開一個串行埠，無論是硬體 COM 埠還是模擬硬體 COM 埠的虛擬串行埠：
// see Microsoft document HOWTO: Specify Serial Ports Larger than COM9.
// https://support.microsoft.com/en-us/kb/115831
// CreateFile() can be used to get a handle to a serial port. The "Win32 Programmer's Reference" entry for "CreateFile()"
// mentions that the share mode must be 0, the create parameter must be OPEN_EXISTING, and the template must be NULL.
//
// CreateFile() is successful when you use "COM1" through "COM9" for the name of the file;
// however, the value INVALID_HANDLE_VALUE is returned if you use "COM10" or greater.
//
// If the name of the port is \\.\COM10, the correct way to specify the serial port in a call to
// CreateFile() is "\\\\.\\COM10".
//
// NOTES: This syntax also works for ports COM1 through COM9. Certain boards will let you choose
// the port names yourself. This syntax works for those names as well.
wsprintf(wszPortName, TEXT("\\\\.\\COM%d"), usPortId);
/* Open the serial port. */
/* avoid to failuer of CreateFile */
for (i = 0; i < 10; i ) {
hHandle = CreateFile (wszPortName, /* Pointer to the name of the port, PifOpenCom() */
GENERIC_READ | GENERIC_WRITE, /* Access (read-write) mode */
0, /* Share mode */
NULL, /* Pointer to the security attribute */
OPEN_EXISTING,/* How to open the serial port */
0, /* Port attributes */
NULL); /* Handle to port with attribute */
/* to copy */
/* If it fails to open the port, return FALSE. */
if ( hHandle == INVALID_HANDLE_VALUE ) { /* Could not open the port. */
dwError = GetLastError ();
if (dwError == ERROR_FILE_NOT_FOUND || dwError == ERROR_INVALID_NAME || dwError == ERROR_ACCESS_DENIED) {
LeaveCriticalSection(&g_SioCriticalSection);
// the COM port does not exist. probably a Virtual Serial Communications Port
// from a USB device which was either unplugged or turned off.
// or the COM port or Virtual Serial Communications port is in use by some other application.
return PIF_ERROR_COM_ACCESS_DENIED;
}
PifLog (MODULE_PIF_OPENCOM, LOG_ERROR_PIFSIO_CODE_01);
PifLog (MODULE_ERROR_NO(MODULE_PIF_OPENCOM), (USHORT)dwError);
PifLog(MODULE_DATA_VALUE(FAULT_AT_PIFOPENCOM), usPortId);
PifSleep(500);
} else {
break;
}
}
if ( hHandle == INVALID_HANDLE_VALUE ) { /* Could not open the port. */
wsprintf(wszDisplay, TEXT("CreateFile, COM%d, Last Error =%d\n"), usPortId, dwError);
OutputDebugString(wszDisplay);
LeaveCriticalSection(&g_SioCriticalSection);
return PIF_ERROR_COM_ERRORS;
}
/* clear the error and purge the receive buffer */
dwError = (DWORD)(~0); // set all error code bits on
ClearCommError(hHandle, &dwError, NULL);
PurgeComm( hHandle, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR ) ;
將ReadFile()在函式內部包裹著，看起來像：
fResult = ReadFile(hHandle, pBuffer, (DWORD)usBytes, &dwBytesRead, NULL);
if (PifSioCheckPowerDown(usPort, aPifSioTable) == TRUE) {
return PIF_ERROR_COM_POWER_FAILURE;
}
if (fResult) {
if (!dwBytesRead) return PIF_ERROR_COM_TIMEOUT;
return (SHORT)dwBytesRead;
} else {
SHORT sErrorCode = 0; // error code from PifSubGetErrorCode(). must call after GetLastError().
dwError = GetLastError();
PifLog (MODULE_PIF_READCOM, LOG_ERROR_PIFSIO_CODE_06);
PifLog (MODULE_ERROR_NO(MODULE_PIF_READCOM), (USHORT)dwError);
sErrorCode = PifSubGetErrorCode(hHandle);
PifLog (MODULE_ERROR_NO(MODULE_PIF_READCOM), (USHORT)abs(sErrorCode));
PifLog (MODULE_DATA_VALUE(MODULE_PIF_READCOM), usPort);
return (sErrorCode);
}
uj5u.com熱心網友回復：
我發現了許多涉及管道的類似發布問題，但是使用重疊 I/O 的相同方法也適用。
- 打破 ReadFile() 阻塞 - 命名管道 (Windows API)
- Win32 API：讀取檔案超時
- 設備驅動程式：Windows ReadFile 函式超時
我還在網路上的Peter 博客上找到了以下文章：Getting a handle on usbprint.sys，其中提供了如何為 USB 連接的設備查找 USB 路徑名的代碼和說明。我在下面的課程中使用了一些代碼示例。
我還在 codeproject.com 上找到了由 Chuan-Liang Teng撰寫的 Enumering windows device的文章，其中包含一個列舉連接的 USB 設備并詢問有關設備的各種設定和詳細資訊的示例。那篇文章中的代碼雖然很舊，但對這個特定應用程式來說不是必需的，但很有幫助。
我有一個使用重疊 I/O 的原型 C 類，它似乎正在復制使用 USB 連接到熱敏列印機的串行埠連接所看到的行為。完整的源代碼和 Visual Studio 2017 解決方案和專案檔案位于我的 GitHub 存盤庫https://github.com/RichardChambers/utilities_tools/tree/main/UsbWindows 中，因為此片段具有最相關的部分。
我在銷售點應用程式中使用修改后的代碼做了一個簡單的測驗，現在正在將它集成到現有的熱敏收據列印機源代碼中，該代碼已經與串行埠配合使用。
#include <windows.h>
#include <setupapi.h>
#include <initguid.h>
#include <iostream>
// This is the GUID for the USB device class.
// It is defined in the include file Usbiodef.h of the Microsoft Windows Driver Kit.
// See also https://msdn.microsoft.com/en-us/library/windows/hardware/ff545972(v=vs.85).aspx which
// provides basic documentation on this GUID.
DEFINE_GUID(GUID_DEVINTERFACE_USB_DEVICE, 0xA5DCBF10L, 0x6530, 0x11D2, 0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED);
class UsbSerialDevice
{
public:
// See https://docs.microsoft.com/en-us/windows/win32/ipc/named-pipe-server-using-overlapped-i-o?redirectedfrom=MSDN
// to implement time outs for Write and for Read.
UsbSerialDevice(const wchar_t* wszVendorIdIn = nullptr);
~UsbSerialDevice();
int CreateEndPoint(const wchar_t* wszVendorId = nullptr, DWORD dwDesiredAccess = (GENERIC_READ | GENERIC_WRITE));
void CloseEndPoint(void);
int ListEndPoint(const wchar_t* wszVendorIdIn);
int ReadStream(void* bString, size_t nBytes);
int WriteStream(void* bString, size_t nBytes);
DWORD SetWriteTimeOut(DWORD msTimeout);
DWORD SetReadTimeOut(DWORD msTimeout);
DWORD m_dwError; // GetLastError() for last action
DWORD m_dwErrorWrite; // GetLastError() for last write
DWORD m_dwErrorRead; // GetLastError() for last read
DWORD m_dwBytesWritten; // number of bytes last write
DWORD m_dwBytesRead; // number of bytes last read
DWORD m_dwWait; // WaitForSingleObject() return value
private:
HANDLE m_hFile;
OVERLAPPED m_oOverlap;
COMMTIMEOUTS m_timeOut;
const unsigned short m_idLen = 255;
wchar_t m_wszVendorId[255 1] = { 0 };
};
UsbSerialDevice::UsbSerialDevice(const wchar_t* wszVendorIdIn) :
m_dwError(0),
m_dwErrorWrite(0),
m_dwErrorRead(0),
m_dwBytesWritten(0),
m_dwBytesRead(0),
m_dwWait(0),
m_hFile(INVALID_HANDLE_VALUE)
{
memset(&m_oOverlap, 0, sizeof(m_oOverlap));
m_oOverlap.hEvent = INVALID_HANDLE_VALUE;
if (wszVendorIdIn != nullptr) ListEndPoint(wszVendorIdIn);
}
void UsbSerialDevice::CloseEndPoint(void )
{
if (m_hFile && m_hFile != INVALID_HANDLE_VALUE) CloseHandle(m_hFile);
if (m_oOverlap.hEvent && m_oOverlap.hEvent != INVALID_HANDLE_VALUE) CloseHandle(m_oOverlap.hEvent);
}
UsbSerialDevice::~UsbSerialDevice()
{
CloseEndPoint();
}
/*
* Returns: -1 - file handle is invalid
* 0 - write failed. See m_dwErrorWrite for GetLastError() value
* 1 - write succedded.
*/
int UsbSerialDevice::WriteStream(void* bString, size_t nBytes)
{
SetLastError(0);
m_dwError = m_dwErrorWrite = 0;
m_dwBytesWritten = 0;
m_dwWait = WAIT_FAILED;
if (m_hFile && m_hFile != INVALID_HANDLE_VALUE) {
BOOL bWrite = WriteFile(m_hFile, bString, nBytes, 0, &m_oOverlap);
m_dwError = m_dwErrorWrite = GetLastError();
if (!bWrite && m_dwError == ERROR_IO_PENDING) {
SetLastError(0);
m_dwError = m_dwErrorWrite = 0;
m_dwWait = WaitForSingleObject(m_oOverlap.hEvent, m_timeOut.WriteTotalTimeoutConstant);
BOOL bCancel = FALSE;
switch (m_dwWait) {
case WAIT_OBJECT_0: // The state of the specified object is signaled.
break;
case WAIT_FAILED: // The function has failed. To get extended error information, call GetLastError.
m_dwError = m_dwErrorWrite = GetLastError();
bCancel = CancelIo(m_hFile);
break;
case WAIT_TIMEOUT: // The time-out interval elapsed, and the object's state is nonsignaled.
case WAIT_ABANDONED: // thread owning mutex terminated before releasing or signaling object.
bCancel = CancelIo(m_hFile);
m_dwError = m_dwErrorRead = ERROR_COUNTER_TIMEOUT;
break;
}
bWrite = GetOverlappedResult(m_hFile, &m_oOverlap, &m_dwBytesRead, FALSE);
}
return bWrite; // 0 or FALSE if failed, 1 or TRUE if succeeded.
}
return -1;
}
/*
* Returns: -1 - file handle is invalid
* 0 - read failed. See m_dwErrorRead for GetLastError() value
* 1 - read succedded.
*/
int UsbSerialDevice::ReadStream(void* bString, size_t nBytes)
{
SetLastError(0);
m_dwError = m_dwErrorRead = 0;
m_dwBytesRead = 0;
m_dwWait = WAIT_FAILED;
if (m_hFile && m_hFile != INVALID_HANDLE_VALUE) {
BOOL bRead = ReadFile(m_hFile, bString, nBytes, &m_dwBytesRead, &m_oOverlap);
m_dwError = m_dwErrorRead = GetLastError();
if (!bRead && m_dwError == ERROR_IO_PENDING) {
SetLastError(0);
m_dwError = m_dwErrorRead = 0;
m_dwWait = WaitForSingleObject(m_oOverlap.hEvent, m_timeOut.ReadTotalTimeoutConstant);
BOOL bCancel = FALSE;
switch (m_dwWait) {
case WAIT_OBJECT_0: // The state of the specified object is signaled.
break;
case WAIT_FAILED: // The function has failed. To get extended error information, call GetLastError.
m_dwError = m_dwErrorWrite = GetLastError();
bCancel = CancelIo(m_hFile);
break;
case WAIT_TIMEOUT: // The time-out interval elapsed, and the object's state is nonsignaled.
case WAIT_ABANDONED: // thread owning mutex terminated before releasing or signaling object.
bCancel = CancelIo(m_hFile);
m_dwError = m_dwErrorRead = ERROR_COUNTER_TIMEOUT;
break;
}
bRead = GetOverlappedResult(m_hFile, &m_oOverlap, &m_dwBytesRead, FALSE);
}
return bRead; // 0 or FALSE if failed, 1 or TRUE if succeeded.
}
return -1;
}
int UsbSerialDevice::ListEndPoint(const wchar_t* wszVendorIdIn)
{
m_dwError = ERROR_INVALID_HANDLE;
if (wszVendorIdIn == nullptr) return 0;
HDEVINFO hDevInfo;
// we need to make sure the vendor and product id codes are in lower case
// as this is needed for the CreateFile() function to open the connection
// to the USB device correctly. this lower case conversion applies to
// any alphabetic characters in the identifier.
//
// for example "VID_0FE6&PID_811E" must be converted to "vid_0fe6&pid_811e"
wchar_t wszVendorId[256] = { 0 };
for (unsigned short i = 0; i < 255 && (wszVendorId[i] = towlower(wszVendorIdIn[i])); i );
// We will try to get device information set for all USB devices that have a
// device interface and are currently present on the system (plugged in).
hDevInfo = SetupDiGetClassDevs(&GUID_DEVINTERFACE_USB_DEVICE, NULL, 0, DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);
if (hDevInfo != INVALID_HANDLE_VALUE)
{
DWORD dwMemberIdx;
BOOL bContinue = TRUE;
SP_DEVICE_INTERFACE_DATA DevIntfData;
// Prepare to enumerate all device interfaces for the device information
// set that we retrieved with SetupDiGetClassDevs(..)
DevIntfData.cbSize = sizeof(SP_DEVICE_INTERFACE_DATA);
dwMemberIdx = 0;
// Next, we will keep calling this SetupDiEnumDeviceInterfaces(..) until this
// function causes GetLastError() to return ERROR_NO_MORE_ITEMS. With each
// call the dwMemberIdx value needs to be incremented to retrieve the next
// device interface information.
for (BOOL bContinue = TRUE; bContinue; ) {
PSP_DEVICE_INTERFACE_DETAIL_DATA DevIntfDetailData;
SP_DEVINFO_DATA DevData;
DWORD dwSize;
dwMemberIdx ;
SetupDiEnumDeviceInterfaces(hDevInfo, NULL, &GUID_DEVINTERFACE_USB_DEVICE, dwMemberIdx, &DevIntfData);
if (GetLastError() == ERROR_NO_MORE_ITEMS) break;
// As a last step we will need to get some more details for each
// of device interface information we are able to retrieve. This
// device interface detail gives us the information we need to identify
// the device (VID/PID), and decide if it's useful to us. It will also
// provide a DEVINFO_DATA structure which we can use to know the serial
// port name for a virtual com port.
DevData.cbSize = sizeof(DevData);
// Get the required buffer size. Call SetupDiGetDeviceInterfaceDetail with
// a NULL DevIntfDetailData pointer, a DevIntfDetailDataSize
// of zero, and a valid RequiredSize variable. In response to such a call,
// this function returns the required buffer size at dwSize.
SetupDiGetDeviceInterfaceDetail(hDevInfo, &DevIntfData, NULL, 0, &dwSize, NULL);
// Allocate memory for the DeviceInterfaceDetail struct. Don't forget to
// deallocate it later!
DevIntfDetailData = (PSP_DEVICE_INTERFACE_DETAIL_DATA)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, dwSize);
DevIntfDetailData->cbSize = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA);
if (SetupDiGetDeviceInterfaceDetail(hDevInfo, &DevIntfData, DevIntfDetailData, dwSize, &dwSize, &DevData))
{
if (wcsstr(DevIntfDetailData->DevicePath, wszVendorId)) {
wcscpy_s(m_wszVendorId, DevIntfDetailData->DevicePath);
}
}
HeapFree(GetProcessHeap(), 0, DevIntfDetailData);
}
SetupDiDestroyDeviceInfoList(hDevInfo);
}
return 0;
}
int UsbSerialDevice::CreateEndPoint(const wchar_t* wszVendorIdIn, DWORD dwDesiredAccess)
{
if (wszVendorIdIn) {
ListEndPoint(wszVendorIdIn);
}
m_dwError = ERROR_INVALID_HANDLE;
// Finally we can start checking if we've found a useable device,
// by inspecting the DevIntfDetailData->DevicePath variable.
//
// The DevicePath looks something like this for a Brecknell 67xx Series Serial Scale
// \\?\usb#vid_1a86&pid_7523#6&28eaabda&0&2#{a5dcbf10-6530-11d2-901f-00c04fb951ed}
//
// The VID for a particular vendor will be the same for a particular vendor's equipment.
// The PID is variable for each device of the vendor.
//
// As you can see it contains the VID/PID for the device, so we can check
// for the right VID/PID with string handling routines.
// See https://github.com/Microsoft/Windows-driver-samples/blob/master/usb/usbview/vndrlist.h
// See https://blog.peter.skarpetis.com/archives/2005/04/07/getting-a-handle-on-usbprintsys/
// which describes a sample USB thermal receipt printer test application.
SetLastError(0);
m_hFile = CreateFile(m_wszVendorId, dwDesiredAccess, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_ALWAYS, FILE_FLAG_OVERLAPPED, 0);
if (m_hFile == INVALID_HANDLE_VALUE) {
m_dwError = GetLastError();
// wprintf(_T(" CreateFile() failed. GetLastError() = %d\n"), m_dwError);
}
else {
m_oOverlap.hEvent = CreateEvent(
NULL, // default security attribute
TRUE, // manual-reset event
TRUE, // initial state = signaled
NULL); // unnamed event object
m_timeOut.ReadIntervalTimeout = 0;
m_timeOut.ReadTotalTimeoutMultiplier = 0;
m_timeOut.ReadTotalTimeoutConstant = 5000;
m_timeOut.WriteTotalTimeoutMultiplier = 0;
m_timeOut.WriteTotalTimeoutConstant = 5000;
m_dwError = 0; // GetLastError();
return 1;
}
return 0;
}
轉載請註明出處，本文鏈接：https://www.uj5u.com/qiye/352711.html