我在Windows上使用ReadFile()從序列槽讀取資料.這個代碼在某個時間點工作正常,但它現在失敗了,我試圖找出問題的根源,是以我懷疑它是串行配置或逾時的問題,因為這些都沒有改變.
ReadFile()傳回false,表示發生了錯誤.但是,當我立即檢查GetLastError()的值時,它傳回0,即ERROR_SUCCESS.讀取的位元組數是0,是以我傾向于認為确實出現了問題,但錯誤代碼完全沒用.
有任何想法嗎？謝謝.
編輯：這是一些相關的代碼片段：
#define GPS_COM_PORT L"COM3"
// for reference, the device communicates at 115200 baud,
// no parity, 1 stop bit, no flow control
// open gps com port
hGpsUart = CreateFile(GPS_COM_PORT, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if (hGpsUart == INVALID_HANDLE_VALUE)
{
if (GetLastError() == ERROR_FILE_NOT_FOUND)
{
msg.setText("GPS COM port does not exist!");
msg.exec();
QApplication::quit();
}
msg.setText("Error occurred while trying to open GPS COM port!");
msg.exec();
QApplication::quit();
}
// set gps com port settings
dcbSerialParams.DCBlength = sizeof(dcbSerialParams);
if (!GetCommState(hGpsUart, &dcbSerialParams))
{
msg.setText("Could not get GPS COM port settings!");
msg.exec();
QApplication::quit();
}
dcbSerialParams.BaudRate = CBR_115200;
dcbSerialParams.ByteSize = 8;
dcbSerialParams.StopBits = ONESTOPBIT;
dcbSerialParams.Parity = NOPARITY;
if (!SetCommState(hGpsUart, &dcbSerialParams))
{
msg.setText("Could not set GPS COM port settings!");
msg.exec();
QApplication::quit();
}
// set gps com port timeouts
timeouts.ReadIntervalTimeout = MAXDWORD;
timeouts.ReadTotalTimeoutConstant = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 50;
timeouts.WriteTotalTimeoutMultiplier = 10;
if (!SetCommTimeouts(hGpsUart, &timeouts))
{
msg.setText("Could not set GPS COM port timeouts!");
msg.exec();
QApplication::quit();
}
// ... later in the code ...
char buf[161] = {0};
DWORD bytes_read = 0;
// This returns false...
if (!ReadFile(hGpsUart, buf, 160, &bytes_read, NULL))
{
// Yet in here, GetLastError() returns ERROR_SUCCESS (0)
QMessageBox msg;
msg.setText("Error reading from GPS UART!");
msg.exec();
}