How does exactly work the "flush" function on the Serial port?

[spaghetti_developer]

Hi everybody,

I'm working with the serial communication port and even though I'm flushing both the buffers (either the receiver and the transmitter) when I go to read the answer to the command I've already sent on the bus I also read the echo of the command. The flush functions are set before the reading procedure then I guessed this functions cleans both the buffers on the serial device but it doesn't do it. So, can anyone explain to me how exactly work the flush function on the serial port?

Thank you in advance.

[asbo]

http://zone.ni.com/reference/en-XX/help/371361J-01/lvinstio/visa_flush_i_o_buffer/ is about as illuminating as it gets.

The node only flushes the receive buffer by default, so it's possible you've left something in the transmit buffer and your device is echoing it back?

[drjdpowell]

Serial devices can be quite slow, so you have probably flushed the buffers long before the device sends back its response (including the echoed command).

Since you know what the command string was, you can easily strip it off the front of the response.

[John Lokanis]

I always flush the buffer, read 10000 chars with 1ms timeout and then send my command. I also make sure that my target is not set to echo the command. (or if it does, I deal with it explicitly).

This has worked well for me in a large system with 100s of ports for many years.