LabVIEW
Serial port with Labview, RTS, DTR
@AeroSoul wrote:
You can use property node to manually set these lines.
The DTR State and RTS State properties.
Yes you can if you want to control those lines yourself. The operators problem is the opposite. He does not want VISA to control those lines at all when it initializes the port and I don't think there is a way to do that other than the solution by JpB (or not use VISA). It can be a problem for instance for interfacing to Arduinos or other similar boards. They consider the toggling of the RTS line as a reset signal.
I think the OP did make an error in his post. I don't see any difference in what he claims to see for Hterm and NI-VISA, which is according to his text of course not what he observes.
@pincpanter wrote:
@rolfk ha scritto:I think the OP did make an error in his post. I don't see any difference in what he claims to see for Hterm and NI-VISA, which is according to his text of course not what he observes.
Do you mean that IOCTL_SERIAL_SET and IOCTL_SERIAL_CLEAR are the same?
That is also unlikely to be exactly the same in Hterm but apparently not the problem of the OP. But the SERIAL_CLR_RTS DOWN/UP and SERIAL_CLR_DTR DOWN/UP calls are the ones he would not want to have been issued on serial port open. Hterm (and all other terminal applications I know of) have a configuration option that defines if RTS and CTS handling should be done at all and if that it disabled they will never try to control those lines.
NI VISA always does this initialization and there is no way to disable it on viOpen() that I know of. viOpen is either called when you do a an explicit VISA Open in LabVIEW or automatically as soon as you try to do anything with a VISA resource to access the underlying port.
Actually I just checked and there might be a small chance. VISA Open has an access mode parameter. One of the values is Load Configuration Settings. This is only supported for VISA ASRL resources but that is what we want here. If you go into NI Max you can configure the serial port with a default baud rate and flow control. If you pass this flag to VISA Open, NI VISA should use the settings as configured in NI Max and MIGHT refrain from trying to initialize the flow control lines during initialization if the flow control settings in NI Max for that port were set to None. I haven't tested this theory myself but it is worth an attempt. Of course you need to execute VISA Open explicitly before trying to access the VISA Resource by any other VISA function. Otherwise LabVIEW will do an implicit viOpen() without that flag set.
