Simple PIC CW keyer

 

I was inspired by a report on building a Rockmite QRP rig by Colin, M1BUU.
This report appeared on the SOTA Reflector, you can read more here.

Now I didn't need a Rockmite, but I did have a few empty PIC chips that are used in the Rockmite (12C508) to provide a very basic iambic keyer. My good friend Gil, ONl12523, helped me program those chips (you may remember him from the OST Morse Box and the Forty Niner PLL projects ...).
My chips were not the "A" variety, but the programming was succesful anyway.OK, now I had a few of those keyer chips ... what to do next ?

First I mounted one on a piece of veroboard, and checked that the circuit worked.
This is the circuit that I made.

To make the keyer a bit more useful in one of my projects (like the 49'er PLL), it had to be put in a suitable box. I have a bunch of old cassette tape boxes, so I decided to give that a try (see top picture).

Not so difficult, drilling a few holes for two 3.5 mm jacks, and a small ON/OFF switch was all it took. An old cellphone battery (Li-Ion/1400 mAh) is powering the circuit. I can charge the battery by connecting it to my lab power supply (set at 4.2V with some current limiting).

I left the pushbutton switch inside the box, it's only needed to set the keying speed.
Press the button for 1 second and a letter 'S' will sound. Pressing the DIT paddle will increase the speed, press DASH to decrease. After a 2 seconds idle time, a short beep signals that you're back in keying mode. That's all there is to it.
Pin 3 of the PIC was used in the Rockmite to obtain a shift of the oscillator, in my circuit this is not used, but the pin is changing state if you have a need for it.

The keyer has no memories or other fancy stuff, it's just adds basic iambic keying to a simple transmitter like a Pixie etc.