13 March 2012

Frequency Reader with Tuning Knob

The "Frequency Reader" is a stand-alone display with three push buttons that allows to read remotely the FT-817 display data and gives minimal user interaction ability. It is supposed to work on FT-857 and FT-897 too.

As of today, March 13th 2012, the "Frequency Reader" supports a tuning knob which lets you retune the radio remotely. The firmware has been tailored for users of microwave transverters, but nothing prevents using it for the usual V/U/HF operations. Three buttons do:
  • USB/CW mode toggle (no action if in a different mode)
  • VFO A/B toggle
  • tuning step selection
Tuning step is selected using the F.R. knob and reminds FT-817 internal steps.

For interested builders, it should be noted that this new firmware works on a slightly different hardware circuit, on which few connections have been moved around to facilitate the design of PCB.

If a simple Frequency Reader is needed, just omit mounting the knob and step button leaving their terminals open.

Technical insight.
The Frequency Reader polls the radio every second for a frequency change, in case the operator touches the front panel dial knob. If the external knob is rotated, the VFO frequency is updated of a "step" amount every 100 ms. If the knob is rotated very fast, the step is increased accordingly in a linear fashion, allowing faster QSY's.

The knob component, a quadrature rotary encoder, must be selected with care. It should have no detents, or generate one step per detent. If it includes a pushbutton, it can be wired to any of the three required buttons mentioned above.

What is left to do.
  • Shoot a short demo video
  • Update the website with the new diagram and firmware
  • Refine the firmware for general public release