This is a Morse keyer by DL4YHF, who designed the circuit and wrote the software 26 years ago. I just designed a new PCB for it. The circuit is practically the same, with only a few minor changes and omissions. I wanted a tiny, low-power device that could be easily adapted for different implementations.

The PCB dimensions are 30×20 mm (1.19″ x 0.77″).

When the keyer is idle and the microcontroller is in sleep mode, the supply current is less than 1 µA. The keyer can be supplied from a coin cell battery or from any other 2 to 5 V DC source.

A suitable battery holder can be soldered directly onto the PCB. Even without an on-off switch, it will take a LONG time to completely drain a CR2032 battery (200 mAh, i.e. 200,000 µAh).

The keyer offers two message memories that can be further subdivided, special contest and beacon modes, as well as other advanced options that you can happily ignore if you don’t need them. It comes with a user manual in multiple languages. The assembly source code is also available.

Links to the original project:

https://www.qsl.net/dl4yhf/pic_key.html

https://www.qsl.net/dl4yhf/keyer_manual_e.htm