C / C++ / MFC

memset(&config, 0, sizeof(config));
config.c_cflag = CS8 | CREAD | CLOCAL; // 8N1, enable receiver, ignore ctrl lines
cfsetospeed(&config, B9600); // baud rate used by the PIC
cfsetispeed(&config, B9600);
tcsetattr(hComPort, TCSANOW, &config);

Jochen Arndt wrote:

I did not see any code that initialises the serial port.

/***** Class Declaration ******************************************************/
class ComPort
{
public:
    ComPort();
    ~ComPort();
    void WriteComPortDataMsg(char *data, char num);
    void ReadComPortDataMsg(char *data, char dlimc);
    void ReadComPortDataMsg(char *data);
    void SetDlimiter(char dlimc);
private:
    char dlim;
    struct termios  config;
    int hComPort;
    bool Error;
};

ComPort::ComPort()
{
    dlim = '\n';
    char c;

    Error = false;
    hComPort = open("/dev/ttyACM0", O_RDWR | O_NOCTTY | O_NDELAY);
    if (hComPort == -1)
    {
        cout << "failed to open port\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }
    
    if(!isatty(hComPort))
    {
        cout << "file descriptor is  not pointing to a TTY device\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin.get(c);
        if ((c == 's' || c == 'S')) Error = true;
    }
    
    if(tcgetattr(hComPort, &config) < 0)
    {
        cout << "configuration of the serial interface not found\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }
    
    //
    // Input flags - Turn off input processing
    //
    // convert break to null byte, no CR to NL translation,
    // no NL to CR translation, don't mark parity errors or breaks
    // no input parity check, don't strip high bit off,
    // no XON/XOFF software flow control
    //
    config.c_iflag &= ~(IGNBRK | BRKINT | ICRNL | INLCR | PARMRK | INPCK | ISTRIP | IXON);
    
    // Output flags - Turn off output processing
    //
    // no CR to NL translation, no NL to CR-NL translation,
    // no NL to CR translation, no column 0 CR suppression,
    // no Ctrl-D suppression, no fill characters, no case mapping,
    // no local output processing
    //
    // config.c_oflag &= ~(OCRNL | ONLCR | ONLRET |
    //                     ONOCR | ONOEOT| OFILL | OLCUC | OPOST);
    config.c_oflag = 0;

    //
    // No line processing
    //
    // echo off, echo newline off, canonical mode off, 
    // extended input processing off, signal chars off
    //
    config.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);

    //
    // Turn off character processing
    //
    // clear current char size mask, no parity checking,
    // no output processing, force 8 bit input
    //
    config.c_cflag &= ~(CSIZE | PARENB);
    config.c_cflag |= CS8;
    
    if(cfsetispeed(&config, B9600) < 0 || cfsetospeed(&config, B9600) < 0)
    {
        cout << "Baud Rate did not set correctly\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }
    
    
    if(tcsetattr(hComPort, TCSAFLUSH, &config) < 0)
    {
        cout << "Configuration set did not work\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }
    
    //tcflush(hComPort, TCIOFLUSH);               // clear comport
}

ComPort::~ComPort() { close(hComPort);  }

Jochen Arndt wrote:

CREAD is probably set but what about CLOCAL?

if(tcgetattr(hComPort, &config) < 0)
    {
        cout << "configuration of the serial interface not found\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }
    memset(&config, 0, sizeof(config));

config.c_cflag = CS8 | CREAD | CLOCAL; // 8N1, enable receiver, ignore ctrl lines
    
    if(cfsetispeed(&config, B9600) < 0 || cfsetospeed(&config, B9600) < 0)
    {
        cout << "Baud Rate did not set correctly\n" << endl;
        cout << "Hit <S> to Stop .." << endl;
        cin >> c;
        c = (char)toupper(c);
        if (c == 'S') Error = true;
    }

read(hComPort, &c, 1);
if ((c >= 0x20) && (c <= 0x7E)) data[cnt++] = c;

Quote:

Return Value
On success, the number of bytes read is returned (zero indicates end of file), and the file position is advanced by this number. It is not an error if this number is smaller than the number of bytes requested; this may happen for example because fewer bytes are actually available right now (maybe because we were close to end-of-file, or because we are reading from a pipe, or from a terminal), or because read() was interrupted by a signal. On error, -1 is returned, and errno is set appropriately. In this case it is left unspecified whether the file position (if any) changes.

int received = read(hComPort, &c, 1);
if (received == 1 && c >= 0x20 && c <= 0x7E) 
    data[cnt++] = c;
else if (received < 0)
    // handle error here

void ComPort::ReadComPortDataMsg(char *data)
{
    int cnt = 0;
    int received;
    char c;

    data[0] = 0x00;
    do
    {
        received = read(hComPort, &c, 1);
        if ((received == 1) && (c >= 0x20) && (c <= 0x7E))
        {
            data[cnt++] = c;
        }
        else if (received < 0)
        {
            
        }
    } while ((c != dlim) && (cnt < 255));
    data[cnt++] = '\0';
}

struct termios

global errno variable

man errno

CPallini wrote:

IDEs are for sissies.

(And yes, I'm old enough to have actually written programs that way. )

char* x = (char*)calloc(sizeof(char),150);
char** p = &x;
free(x);
x = NULL;
printf("%p\n", *p); // here *p is NULL

CPallini wrote:

*p is NULL