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Simple (maybe) learning project: A Keyer

With a few 8 bit 8 pin microcontrollers from a thrift store find and the other parts and pieces in the shack, the idea of building a keyer came to mind as a simple project for learning about these devices. A keyer is just a switch, right? Maybe not.

A keyer is a user interface device that takes input from two switches to produce a keying pattern for a transmitter to send Morse code. The idea is to make it easier to send faster speeds with less operator fatigue. The most common device with two switches is called an iambic keyer because it will send alternating dots and dashes when both keys are pressed simultaneously sounding like a poem with iambic pentameter. That makes it a three state device: dots, dashes, and alternating.

But wait! there’s more! What does the keyer do when both keys are released? Several ideas have been tried. Iambic A just stops sending whatever pattern it is sending while Iambic B sends an additional completing alternate element. Then there’s the Ultimatic method where the last key pressed of both overrides the first. Finally, there’s slap keying which is like the old straight key in that it doesn’t know anything about two switches and automated dots and dashes. Slap just sees a switch closed and feeds that directly to the transmitter as-is. Then maybe there should be a “super slap” that will do automated length dots and dashes but consider both switches closed as a straight key mode or something.

A keyer also presents issues in configuration and control. Besides keying mode, the operator needs to set keying speed, whether right or left handed, ratio adjustments (called weight), audio output, and memorized messages. Figuring out how best to be able to control all these things is a user interface challenge.

In some respects, the keyer and iambic paddle are previous generation devices. These days, it is very simple to just use a keyboard with a microcontroller. A standard PS2 keyboard needs only clock and data lines in addition to the power leads and has all sorts of keys than can be used to control various options and configuration settings.

There are other factors to consider as well. The 8 pin 8 bit PIC12f683’s in the junkbox have 2k program memory and 256 bytes EEPROM. They will run off a lithium coin cell at very low power levels. Standard clock speeds run instructions at about 1 microsecond each. A lot to figure out!

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