Hi friends,

     I´m trying to develop different drivers for rs485 and rs232 port. In the last post I described my problem with rs232 port and now I have a question for rs485 port. I want to write and read using the rs485 port. When I use the functions for write (change speed, parity, ...) I have no problem with them but my problem appear when I want to read. I use the same functions that work properly for rs232 port but the driver stop to work and the SmartServer reboots itself when I use the read functions.

   The source code that I use for read is the next:

I want to if there is somebody that have work with this port and read information properly.

Best regards,

     Alex

hi alex,

you cannot use ioctl(_rs485_fd, FIONREAD, (int)&nBytesToRead); to determine how many bytes to read. this will result in a call to rs232 with a potentially invalid handle.

you need to use rs485_read( _rs485_fd, Line, nBytesToRead ) with a specific buffer size (nBytesToRead). rs485_read() returns the number of bytes that really were read. please see also the Programmability Tools User's Guide, appendix a, page 222: description of rs485_read() (especially the length parameter).

note: looking into the readme of the new SmartServer Service Pack 2, there has also been a bugfix regarding rs485. so i would recommend using SmartServer Service Pack 2

/best