Error-1073807339 when connect RS232 port to NI MAX

Hi all,

My device is a RS232 port connection. I can send and read command successfully by serial port utility. But when I used NI MAX VISA test panel and continues write and read.vi from the labview example, errors occurred.  The error is 1073807339-VISAHex 0xBFFF0015) Timeout expired before operation completed). When the command is successful, it will return a string ':A  Number'. The settings in serial port utility and NI MAX are attached.

Thanks,

Mei