STM32F0 based CW beacon generator. For schematics please see my web page: http://e.pavlin.si/2016/02/03/stm32f070-usb-miniature-dongle-for-prototyping/
Connect small speaker to port PA6 and LED or PTT signal to PA0
Download the VCP driver from http://www.st.com/web/en/catalog/tools/PF257938# Connect the device, use terminal and have fun.
... work in progress ...
Check e.pavlin.si web page for more details and hardware resources.
Here is shortcut to working device: make single sided PCB, assemble all components, download and install DfuSe from http://www.st.com/web/en/catalog/tools/FM147/CL1794/SC961/SS1533/PF257916 and update firmware with the DFU file https://github.com/s54mtb/stm32projects/blob/master/projects/f0-usb-beacon/Objects/MorseGenerator.dfu