But what does this mean?
I looked at the code, it looks like TC do not get a serial port when it initializes the GPIB interface, but instead a dummy interface. The dummy interface is returned when no name matches the special serial port name.
That is the reason I say to right click in the address field (On load device page for a serial device) to get the correct serial port name.
I have not been able to get this working on Linux, so I did some further experiments with TestController tonight.
I generally work on Linux, but I tried running TestController using a Windows 10 virtual machine. After re-directing the serial port to the virtual machine, installing Java on Windows, I then set up TestController in exactly the same way as I did on Linux, except for the port name. On Windows I did get a drop-down listing the serial ports on the devices tab and from this I was able to identify COM3 as the port being used by the AR488. After sertting up I clicked on Reconnect and got taken to the Commands tab as usually and saw an "Invalid Device" error telling me that the response from the AR488 was 'null'. This was at least a different response to what I had been getting on Linux. I then remembered that when connecting to the serial port on some Arduino boards, it takes a couple of seconds for the board to restart, so I used the 10uF capacitor trick to prevent the reset pulse and that worked. The HP34401A was now correctly identified, could be controlled and TestController received readings from it. So far so good. Incidentally, I like the ability to turn the display on and off!
I then went back to Linux an tried exactly the same thing. As previously, there was no drop-down listing the serial ports and I was not able to connect to the 34401A at all.
I then went back to Windows a second time and everything still worked as it had done previously.
The experiment was useful. It shows that I was using the correct procedure for setting up and that TestController works fine with an AR488 and the Agilent 34401A on Windows. However, evidently, for some reason, it does not recognise serial ports on Linux. I wonder, does it work on a Mac? On Linux I get no drop down list of serial port, and as noted earlier, the program seems to be defaulting to a dummy port.
I wonder whether it might be useful to add a configuration option to add a delay after connecting to the serial port and attempting to get a response from *idn? command via the AR488 controller. That might avoid the need to the capacitor workaround. Perhaps this is already possible by putting something in the Settings field in the GPIB interfaces dialogue?
I would be happy to contribute and have a look at what the problem on Linux is, but I don't see the sources published anywhere?
I would also like to add a short TestController setup section to the AR488 manual. I have already captured some screenshots while testing this evening, but it would be useful to be able to show it working on Linux as well if possible.
In any case, thank you for making this program available and I appreciate your adding support for the AR488.