Simple question about XON/XOFF (repost from the LV Software board)

[Rick Nelson]

Hello,

I'm using LV 7.1 to send/receive commands from a microcontroller via the serial port. My specs say that XON/XOFF software control will be used to throttle data during the transfer. Then the specs then go into detail about how XON is ASCII character 17, and is transmitted after a Break when the receiver is ready for data, as the same with XOFF being ASCII 19 and how its is transmitted after a Break, and then how the transmitter is restricted to sending out 8 bytes after a Break->XOFF command is received... etc.

My question is: Do I need to write LabVIEW code to handle/look for Breaks, or are the deetails handled in the VISA/LabVIEW drivers? I would think that it is handled by VISA, but the fact that the details of using the Break command are right in the specs might mean that this scheme is specific to our microcontroller (which isn't built yet, so I can't test on it).


Thanks for any replies!

-- Rick

[Shawn B.]

Rick,

The software handshaking scheme you described is exactly how XON/XOFF flow control works. This is not a method specific to your device.

XON/XOFF flow control is already implemented in VISA, so you do not need to write your own code. You can enable the XON/XOFF flow control with a VISA property node, or the Configure Serial Port VI (actually just calls a VISA property node).

Shawn B.
National Instruments