Sunday 3 February 2013


Now I've broken my duck with Arduino, it's time to look at some applications.

Having already got the "made a keyer" T-shirt for PIC and Raspberry Pi, the implementation of a Keyer seems to be turning into my "Hello World" example for microcontrollers, so off we go again with the "KEYERduino"...

Here's the program (what the illuminati call a "sketch" in Arduino-speak):

It is all simple enough - three input "buttons" being read and generating a digital output - just an extension of the button tutorial on the Arduino website.

In the present case, not only does the LED associated with pin 13 light up - we're also thinking of the same digital output driving the base of an open-collector transistor to key the transmitter. Also, only the straight key input works precisely like the button tutorial, simply "lighting the LED" when pressed. Closing any of the other two "buttons" triggers generation of the "dits" and "dahs" of Morse code, making an "iambic keyer". Oh yes - I nearly forgot - I also included a nasty, square-wave sidetone generator.

Here's the circuit, expressed in the unique format of Fritzing, much beloved of the Arduino community...

Fritzing isn't really my cup of tea - its OK for generating the sort of easily-accessible images above but it seems very much harder to make proper schematics with Fritzing than with a tool like Eagle.

Of course, nobody in their right mind would permanently implement a Keyer on an Arduino - it simply isn't worth burning the value (~£14) of the Arduino in something as trivial as a keyer. But there are some cases where it might just be excusable:
  • As a learning exercise - beyond the button tutorial
  • When part of a more complex application - such as a MEPT beacon
  • When you are just using the bare chip in a home-brewed board - cheap as chips!
Anyway - here's my keyer, running on the cheaper-than-chips WOTDUINO...

Not only is my implementation reasonably cheap (~£4). Not only was it an interesting learning exercise. But also, it might be the start of a more complex ham radio application of the WOTDUINO. Watch this space!

 ...-.- de m0xpd

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