Windows 10 ARM64平台MFC串口程序开发

Windows 10 IoT ARM64平台除了支持新的UWP框架，也兼容支持老框架MFC。使得用户在Windows 10 IoT下可以对原MFC工程进行功能升级，不用在新框架下重写整个工程。熟悉MFC开发的工程师也可以在Windows 10 IoT平台下继续使用MFC进行开发。

本文展示MFC串口程序开发，及需要注意的地方。

1. 创建MFC工程

1. 打开visual studio 2022，点击“创建新项目”。

2. 选择筛选条件，语言C++，平台选择Windows，应用类型选择桌面。

3. 选择“MFC应用”，点击下一步。

4. 应用程序类型选择基于对话框，其它选项默认，创建好工程。

2. 界面设计

拖动工具栏中控件到设计窗口中，设置好控件属性，绑定好控件变量名及消息响应函数。此处与传统MFC程序开发一样。

3. 串口代码

可以参考文章《UWP串口程序开发》，使用新Devices库查询串口，打开串口，读写串口。本文依旧采用传统的接口Createfile，WriteFile，ReadFile操作串口。

3.1 查询串口

已知串口名，可以直接通过CreateFile打开串口。或者通过API接口进行查询。

#include <cfgmgr32.h>
#include <propkey.h>
#include <initguid.h>
#include <devpkey.h>
std::wstring devicePath;
devicePath = GetFirstDevice();
Handle serialHandle= CreateFileW(devicePath.c_str(),GENERIC_READ | GENERIC_WRITE,0,NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,NULL));
//Handle serialHandle= CreateFileW(L” \\\\?\\ACPI#NXP0113#2#{86e0d1e0-8089-11d0-9ce4-08003e301f73}\\SERCX”,GENERIC_READ | GENERIC_WRITE,0,NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,NULL));std::wstring GetFirstDevice ()
{ULONG length;CONFIGRET cr = CM_Get_Device_Interface_List_SizeW(&length,const_cast<GUID*>(&GUID_DEVINTERFACE_COMPORT),nullptr,        // pDeviceIDCM_GET_DEVICE_INTERFACE_LIST_PRESENT);if (cr != CR_SUCCESS) {throw wexception(L"Failed to get size of device interface list. (cr = 0x%x)",cr);}std::vector<WCHAR> buf(length);cr = CM_Get_Device_Interface_ListW(const_cast<GUID*>(&GUID_DEVINTERFACE_COMPORT),nullptr,        // pDeviceIDbuf.data(),static_cast<ULONG>(buf.capacity()),CM_GET_DEVICE_INTERFACE_LIST_PRESENT);if (cr != CR_SUCCESS) {throw wexception(L"Failed to get device interface list. (cr = 0x%x)",cr);}return std::wstring(buf.data());
}

3.2 打开串口

与WINCE不同，Windows 10 IoT需要用FILE_FLAG_OVERLAPPED异步操作模式打开和读写串口，如果使用同步操作模式打开串口进行读写，读写效率会有影响。

HANDLE m_hComm = CreateFile(Port, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, 0);

设置串口参数

GetCommState(m_hComm, &dcb);                                  /* 读取串口的DCB */
dcb.BaudRate = 115200;
dcb.ByteSize = 8;
dcb.Parity = 0;
dcb.StopBits = 0;
dcb.fBinary = TRUE;
dcb.fRtsControl = RTS_CONTROL_DISABLE;
SetCommState(m_hComm, &dcb);                                  /* 设置串口的DCB */

3.3 读串口

异步操作模式需要设置OVERLAPPED

#include <wrl.h>
using namespace Microsoft::WRL::Wrappers;
auto overlapped = OVERLAPPED();
overlapped.hEvent = overlappedEvent.Get();DWORD bytesRead = 0;
if (!ReadFile(pDlg->m_hComm,reinterpret_cast<BYTE*>(recvBuf),1024,&bytesRead,&overlapped) && (GetLastError() != ERROR_IO_PENDING)) {DWORD error = GetLastError();
}if (!GetOverlappedResult(pDlg->m_hComm,&overlapped,&bytesRead,TRUE)) {DWORD error = GetLastError();
}if (bytesRead != 0)
{OnCommRecv(pDlg, recvBuf, bytesRead);			/* 接收成功调用回调函数 */
}

3.4 写串口

用异步模式写串口

auto overlapped = OVERLAPPED();
overlapped.hEvent = overlappedEvent.Get();if (!WriteFile(m_hComm,psendbuf,len,&dwactlen,&overlapped) && (GetLastError() != ERROR_IO_PENDING)) {DWORD error = GetLastError();
}if (!GetOverlappedResult(m_hComm,&overlapped,&dwactlen,TRUE)) {DWORD error = GetLastError();
}