LabVIEW
Re: DTR state while serial port init
I run "VISA Configure Serial Port (Instr).vi" directly without any other action ("VISA Open") before and I also tried to set the property at first in the configure VI, but the DTR still gets changed.
Even when the first action is to clear the DTR, the DTR internally gets set for a short time period which resets the Arduino.
Read the property back on (11) says it got set properly to 0.
Is there no way to handle the interface on this way, that it does not touch the DTR line during the port init?
@michaeluray wrote:
Is there no way to handle the interface on this way, that it does not touch the DTR line during the port init?
The underlying viOpen() function does a default initialization of the serial port and there is likely nothing you can change about that. And while VISA Open calls that viOpen() function internally, you gain nothing by omitting the VISA Open node, since LabVIEW calls viOpen() anyways the first time it encounters a VISA node that tries to access a specific resource. Each VISA resource name also stores internally the underlying VISA session handle that is ABSOLUTELY necessary in order for anybody to use any of the other VISA functions and the only way to receive such a session handle is by calling viOpen().
There isn't in terms of software. VISA allows control of those handshake lines. In order for that to work it needs to initialize these lines when opening the serial port under Windows. If it doesn't it can't later go and decide to want to control it anyhow if you use one of the property nodes. But when it tells Windows that it wants to control these lines eventually the Windows COMM system sets them explicitly to a state.
VISA either has to tell Windows that it wants to use those lines or it would have to jump later through hoops and loops to still be able to control them when you decide to use one of those modem line properties.
