Hi Matthew and Group,
One item on my list is to have remote CW for the HL2. This is what I am currently thinking:
** Enable CWX in PowerSDR as a start.
** Connect a CW key or paddle to the host PC via MIDI. This can be done with a <$10 arduino or teensy and
this library. There are lots of hits and examples if you google arduino teensy and MIDI. the MIDI infrastructure is tuned for low latency. I use a musical MIDI (USB) keyboard at home with sound produced by the PC and latencies are not noticeable. If they were humanly noticeable, people would not use virtual MIDI instruments. SparkSDR already knows about MIDI.
** Create a small program on the host to generate the side tone and send UDP packets. The side tone would use
ASIO or equivalent low latency audio drivers. I would like to open another ethernet port on the HL2 to accept simple side traffic to the HL2. It is a lot of overhead to support the full protocol and I would like to be able to send things like CW key down/up/dot/dash via an asynchronous side channel still using UDP while other software runs. The user side tone experience at the PC should still have unnoticeable latency. The actual CW reaching the HL2 may have ~30ms latency, but compare that to 66ms for radio waves to travel half way around the earth.
** In the longer term, I'd like to develop this simple side channel to accept TX information such as amplitude, frequency, phase and duration of a tone. This would allow us to send WSPR and FT8 at a low level so that enough information is present in the HL2 to null out harmonics. I did experiments along these lines years ago and would still like to develop this. Imagine no N2ADR filter board required for some modes of operation. This would also allow use to shape the CW tone sent to the HL2 and offload that task from the HL2 while providing the flexibility of software.
I have stopped work on any local sidetone at the HL2 using PWM and the circuitry on the front panel. It is a step towards forcing an operator to sit in front of the HL2 that I would like to avoid, plus it is a half measure without mixing/headphones, etc, that will never truly satisfy someone who wants to sit in front of the HL2. There are other solutions if you really really want to operate in front of your HL2.
It is all a matter of time and priorities so I won't make any promises for delivery dates. I have too many irons in the fire. If you or anyone wants to work along these lines, I am happy to provide help and assistance.
In my opinion, this is what *software* defined radio is about: moving as much functionality from hardware to software as can sensibly be done. Also, it still keeps the Hermes-Lite *Lite* and true to the original objective.
73,
Steve
kf7o