Deep Dive Question: FDM-SW2 to FDM-DUO method of control #comport #fdm-duo #fdm-sw2 #wsjt-x #fldigi

Patrick Bouldin KM5L <patrick@...>

I've been doing a lot of research today, just trying to figure out the interaction of frequency and mode control between the DUO and the other devices. Here's what I've noticed using the VSPE monitor, and using VSPE splitter and devices attached:
  • Any application, like WSJTX or FLDIGI will request frequency and mode over the outbound COM port assigned within the application (I saw the data going outbound on COM port)
  • Any application will receive the frequency and mode over the inbound COM port assigned within the application (and I noticed that the inbound is ALL shared when using VSPE, same inbound info is sent to all inbound devices, including FDM-SW2 RX devices (saw the data coming inbound on COM port)
--- but here's the kicker ---
  • I noticed that if you change the frequency of any RX channel (like RX1, RX2, RX3, or RX4) from FDM-SW2 app by sliding the bar, it does change the FDM-DUO VFO frequency, but there is no CAT data transmitted from the FDM-SW2 RX COM out port
Which leads me to my hypothesis that the when the slider on FDM-SW2 is moved on any RX, the resulting change in frequency on the radio must not be going over the CAT COM port, right? It must be going over the other USB where the radio/SW2 integration is being done?

Why do I care?  I don't know, I guess it will help me debug if problems surface. I have noticed, that out of the most recent 20 posts that 4 of them (20%) might be avoided (or frustration averted) if we can tackle how the COM ports are configured - and what I mean is the underlying understanding,
not just literal instruction based on situations. As many know, there are many ways to "luck out" with certain settings, only to die because of one reason or the other, and hard to battle back if you don't understand why things are happening.

73, Patrick KM5L

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