But I did see the error code -194 being returned. Does that means that my program has encountered the RS232_NEXT_FREE_ERROR?

I believe RS232_NEXT_FREE_ERROR is the next error code available to the RS232 class. It should be unused, and I don’t think you will ever see it returned.

- Mark

Do you know what is RS232_NEXT_FREE_ERROR? Does it just mean that it is not a known error in the predefined enumeration? Is there any advice that you can give to help on the problems that I am facing?

Thanks.

Crystal

I tried my serial communication program on the actual hardware where the receiving serial port only has 3 pins(GND, RX and TX). It is on a self customzied PCB board. Initially, the receiver was able to receive the serial message. After 30 mins, my program had an error when sending. The error code is -194 (RS232_NEXT_FREE_ERROR). May I know what this error mean? What do you suggest I do?

Thanks.

Crystal

Sounds like you have a flaky hardware setup. Maybe you should try using a cable to connects the appropriate control lines.

- Mark

Thanks for your reply. I tried setting dtr, xon_xoff, rts_cts and dtr_dsr to DISABLE. The receiving PC was initially able to receive the serial message. After 20 mins plus, the receiving PC was not able to receive the serial message and I got a -198 (RS232_PORT_NOT_FOUND) error code printout on my command prompt. What do you think cause the failure to send the message? If dtr is set to UNCHANGED, the receiving machine is still able to receive the message 2hrs later.

void SerialConnection::initRS232(const string &port,
long baud_rate ,
char parity ,
int word_length ,
int stop_bits ,
int dtr ,
int rts ,
int xon_xoff ,
int rts_cts ,
int dtr_dsr )

Thanks
Crystal

If you haven’t connected the DTR and RTS lines, it doesn’t matter what you set them to.

But you definitely want to make sure you don’t turn on DTR/DSR or RTS/CTS handshaking – both of those settings must be turned off.

XON/XOFF depends on the interface you have with the other end.

The difference between UNCHANGED and DISABLED is that if you set a line to UNCHANGED, the driver doesn’t attempt to modify whatever the current setting is.

- Mark

If only the RXD, TXD and GND pins of the serial ports are connected, what values should I set for the dtr, rts, xon_xoff, rts_cts and dtr_dsr parameters in the initRS232 function below? What are the differences between using UNCHANGED (-1) and DISABLE (0)?

void SerialConnection::initRS232(const string &port,
long baud_rate ,
char parity ,
int word_length ,
int stop_bits ,
int dtr ,
int rts ,
int xon_xoff ,
int rts_cts ,
int dtr_dsr )

Thanks
Crystal

I developed a serial port programming language specially designed to simplify the development of RS232 based applications and it is freely available on sourceforge.

Would you please take a look and let me know your thoughts ?

You can download the application from https://sourceforge.net/projects/anyserialport and get more information from the project website ( http://www.anyserialport.com )

Thank you

Orhan

The sample program is in the CHAP12 folder of the source CD. Have you checked there?

- Mark