Hi Elliott,
I popped an RS Line Tester onto the COM1 Port connected to the CT-17 232/TTL Interface. It’s a RS232/422 hardware/software analyser. After Windows Boot and COM Port initialisation, all Lines go Low, except RX/TX which stay mid-state - “Off”. All as expected.
On running WSJT-X or FLDigi - both already set for an Icom 736 on COM1, the DTR Line goes High - as per the software settings. The TX/RX Data Lines twinkle away, and I have full Rig CAT control. On Exiting WSJT-X or FLDigi, both, quite correctly, re-initialise the COM Port (normally 9600/8/1/N, Handshaking Lines - Low).
As I predicted, WFView leaves the Handshaking Lines “as is”, and with many Serial Adapters wanting one of more of the Handshaking Lines High, there will be some, or no, control over the Rig (see later).
The TX Line twinkles every 400mS, with random flashes on the RX Line, and no Rig CAT Control. Within the Analyser software I can toggle DTR “High” - and then WFView immediately starts to operate correctly - regular TX/RX every 400mS and full CAT control over the Rig - including the Read-Back of the Frequency. The Icom CT-17 therefore does need DTR “High”, even though there is no technical reason or requirement for this.
I say some, or no, control, of some Interfaces - depending on the design of the Interface. Some, such as “Dongles” - which are still made and are for sale today, use the DTR or RTS as a Power Source. In this case, without DTR (or RTS) “High”, the Dongle just doesn’t work (excepting perhaps for a separate PTT from RTS or DTR).
Looking back at my notes of 1991, the original Kenwood Interface uses the DTR Line to “Enable” a NE555 used to derive a Neg Power Line. Without DTR “High”, the Interface fails to work. Once correctly powered, the Interface then toggles the DSR Line “High” to tell the software that a genuine Kenwood Interface was connected. The Kenwood Service Manual does not show the DTR/DSR connections, but does mention that the Interface “will only work with their Control software”.
The Icom CT-17 uses the DTR Line to Enable the MAX232 RX Data Line - without this there are very erratic results from the Rig - or nothing at all. Again, not a technical requirement, and this circuitry is not shown in the Service Manual.
Remember, the CI-V Protocol is a Single Wire (bi-directional) Model, and with some configurations TX Data may be “echoed” - which can cause confusion when an Interface is not operating correctly. TX Data can be confused as RX Data, where control software can interpret things as operating correctly.
Many people consider that RS232 and 422 have had their day, and are old-fashioned technology. “USB is the only way forward”, they cry. But look at all the Amateur Radio Forums (“Fora”?) with comments such as: “My CAT Comms fail when I transmit”, and: “Why can’t I buy a USB Cable more than 1.8m long?”. Then there is the price of decent toroids to wrap your USB cables around, or sourcing decent screened USB Cables. And the price of USB Opto-Isolators to remove ground loops.
MIL Spec RS232/RS422 with IP Rated lockable Connectors are still in-vogue, with double screened cables with separate Signal Ground and Earth… No stray RF problems there!
A further off-topic comment - "Why did the Makers produce Interfaces that don’t technically require Handshaking Lines to go “High”, but have done so, and then don’t show that in the Service Manuals? Money of course… Back then you needed to buy both the Interface and the software. And look at Icom now, with the RA-BA1 software at over £100 (or $100), Win4Icom at half that cost, and WFView, very generously available at no cost to us. Thanks Elliott!
Anyway, what I envisage in a later version of WFView is some Buttons along the lines of WSJT-X. Two buttons: “DTR State” and “RTS State” , of which none, either, or both can be toggled to “High”. Then: “PTT requires RTS or DTR”, with corresponding RTS and DTR Buttons. If DTR has been set to “High”, then only “RTS PTT” can be enabled, and conversely, if RTS has been set “High” then only DTR can be enabled. (otherwise the Rig may transmit when you fire-up WFView…)
As I said earlier RS232 usage my have waned, but it is still used, and as WFView gets more popular, I can envisage this problem occurring more frequently, and being able to select the Handshaking Lines should cover 99.9% of Serial Interfaces without hardware modifications.
Thanks again to all, and to Elliott,
Regards and best 73
de Peter G6EPN