Unfortunately this example did not make me happy so I decided to convert it into a simple Arduino Library ... also use set_data_callback_in_frames which uses frames instead of bytes. In Arduino you ...

Added to that a MIDI-in, so you can combine the created midiclock with other midimessages. Everything was loaded unto an Arduino Nano with an ATMEGA328P chip. Midi-in via RX in, MIDI-out via TX-out.