LabVIEW
VISA (COM) STATUS
Solved!
@Faizan_habib wrote:
Is there any other way to check if the port is connected?
1. Send a command and read the response.
2. Depending on the device you are connected to, you could check the handshaking lines. No promises here as there are many hardware reasons this could not work.
@RTSLVU wrote:
You could search for available com ports.
While this returns all installed serial ports (that VISA has found on the system), it does not say anything about if anything is connected to them. The only way to detect that is by trying to attempt to communicate with the device. This requires to know at least one command that the remote device understands and which will produce a response. There is no other way since at the time the serial port was invented the fact that you could communicate with a device through just a receive and transmit data line was quite revolutionary. USB and other buses later explicitly added extra protocol elements to the specification for managing the connection itself but serial port has no such common basic protocol elements.
@Faizan_habib wrote:
Thanks for your reply. I have tried to communicate with the device and its working fine. But the point is that I want my code to know that there is a connection and on that basis i want to implement some logic.
And as I have already commented, that requires you to try to communicate with the device. With proper error handling you can detect if a port is connected to your device or not.
While the LabVIEW beginner often forgets to even connect the error clusters, the next step is to just connect them all through and error out whenever something causes an error. But real world applications never will be able to work that way. There can be errors sometimes that are expected and should be ignored, others that indicate to retry the operation as it usually will work the next time and then there are the ones that are real errors and indicate that you simply need to give up. Programming real world applications is among other things to know when what sort of error happens and how to deal with it.
In this specific case you would likely have to enumerate all the serial ports as RTSLVU showed you, then go through each and try to communicate with it, By using a short read timeout you can limit the time needed to go through all ports. If there is a timeout error, there is either no device that can respond or now device that knows about the command you tried and you can ignore that error and try with the next port. If you get a response, you can check that to be the expected one. For instance if your device supports an identification query you could issue that command and if there is a successful response, check that to contain the expected device identifier.
Rinse and repeat for every port in your system until you scanned them all (or you found the first port that responded as expected).
