A simple Arduino Beacon Keyer

The ArKeyer.ino arduino script implements a CW keyer for
radio beacon transmitters. This code was written for the DigiSpark
Arduino (based on an ATtiny see http://digistump.com/).

Configuring the Code

Add your call and grid to ArKeyer/ArKeyer.ino (see the
two lines that start with "#define CALLSIGN" and "#define GRID"

If your call was k4kdj and you were in grid EM97SF, the lines
would look like this:

// callsign (all upper case, please....)
#define CALLSIGN "K4KDJ/B"
// Your grid
#define GRID "EM97SF"

Optionally, you may adjust the "dead carrier time" by changing the
value of the CARRIER_TIME from 5 to some other value (in seconds)

#define CARRIER_TIME 5

By default the speed is set to something near 13 words per minute.
Change this by modifying the WPM constant

#define WPM 13

Building the Code

This code has been tested under Arduino 1.6.6 with the Digispar support.

Select the "Digispark default 16.5 MHz" board in the Tools->Board menu.

Then hit the compile/upload button and follow the directions.

Connecting the Keyer

Pin P2 goes HIGH for keydown, while P0 goes LOW for keydown.
Select the one you want. Note that both pins are driven by
"totem-pole" outputs -- no open collector here. Neither should
be expected to drive much more than 10 mA.

Connect Vin to a DC source of between 7 and 35 volts.
OR connect 5V to a 5V source.

Connect GND to ground.

Connect the keying line to either P2 (active HIGH) or P0 (active LOW).

Fire it up and listen to the beacon!

Good luck and 73.

A Case

The DigiSpark is a neat little board, but you might not want it
flopping around inside a box. I often use double-sided tape or
velcro to anchor it to a nearby surface. Alternatively, I've
designed a small box suitable for 3D printing. I've printed
about a half dozen of these on my Monoprice Select Mini 3D
printer.

I designed the boxes in FreeCAD. The
design files are located in the Case subdirectory. DigiSparkCase.fcstd
is the FreeCAD design file. If you don't want to install FreeCAD,
you can use the included DigiSparkCase.stl file as input to any reasonable
3D slicer.

matt, kb1vc