c++ - Set DCB Fails When Attempting to Configure COM Port -

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i'm trying write c++ mfc application uses serial port (e.g. com8). every time try set dcb fails. if can point out i'm doing wrong, i'd appreciate it.

dcb dcb = {0};  dcb.dcblength = sizeof(dcb); port.insert( 0, l"\\\\.\\" );  m_hcomm = createfile(     port,                           // virtual com port     generic_read | generic_write,   // access: read , write     0,                              // share: no sharing     null,                           // security: none     open_existing,                  // com port exists.     file_flag_overlapped,           // asynchronous i/o.     null                            // no template file com port.     );  if ( m_hcomm == invalid_handle_value ) {     trace(_t("unable open com port."));     throwexception(); }  if ( !::getcommstate( m_hcomm, &dcb ) ) {     trace(_t("cserialport : failed comm state - error: %d"), getlasterror());     throwexception(); }  dcb.baudrate = 38400;               // setup baud rate. dcb.parity = noparity;              // setup parity. dcb.bytesize = 8;                   // setup data bits. dcb.stopbits = 1;                   // setup stop bits.  if ( !::setcommstate( m_hcomm, &dcb ) ) // <- fails here. {     trace(_t("cserialport : failed set comm state - error: %d"), getlasterror());     throwexception(); }

thanks.

additional info: generated error code 87: "the parameter incorrect." microsoft's most useful error-code. j/k

my money on this:

dcb.stopbits = 1;

the msdn docs says stopbits:

the number of stop bits used. member can 1 of following values.

onestopbit    0    1 stop bit. one5stopbits  1    1.5 stop bits. twostopbits   2    2 stop bits.

so, you're asking 1.5 stop bits, such horribly archaic thing can't remember comes from. teleprinters, possibly.

i'd guess chances of driver/hardware supporting mode slim, hence error.

so, change dcb.stopbits = onestopbit;


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