Features (version 1.0):

 - 10 tempo outputs: 48 ppqn, 24 ppqn, 8 ppqn, 4 ppqn, 2 ppqn,
                     1 ppqn, 2 ppwn, 1 ppwn, 0.5 ppwn, 0.25 ppwn
 - Roland type Start/Stop and Continue outputs
 - Sync24 DIN socket
 - MIDI Thru
 - MIDI activity LED
 

Schematics, PCB layout, program, and source files (version 1.0)
 
 

Part list:

Resistors (1/4W carbon or metal film):
3x 220R
1x 360R
1x 1k2

Capacitors:
2x 22pF ceramic
2x 100nF ceramic multilayer
2x 47uF/25V electrolytic

Diodes:
5x 1N4148
1x LED of your choice

ICs:
1x AT90S1200
1x 6N137
1x 78L05

Other:
1x 4MHz cristal/resonator
1x 20pin DIP socket
1x 8pin DIP socket
3x DIN 5pin connectors
10x 1/4" or 1/8" jacks
1x connector for power supply of your choice

1x PCB (or protoboard)
1x case to put everything in
1x Power supply (up to 18V DC or 12V AC)
 

Circuit description:

    This is pretty much straight forward. MIDI input is separated
from the rest of the circuit by an optocoupler. The signal from the
opto is then passed to AVR, which generates MIDI Thru signal and
drives activity LED.
From the AVR, the 24 ppqn tempo, Start/Stop, and Continue lines are
connected to the DIN Sync socket. All the lines go to PCB connectors
which can be fitted with 1/4" or 1/8" connectors on the front panel.

Using the device:

    DIN sync converter is used to sync some of pre-MIDI drum machines
and sequencers (e.g. all those X0X Roland boxes) to MIDI. Additional
output jacks are used for synchronizing other devices (e.g. analog
sequencers).

    Connect device to MIDI and to device you want to synchronize
using either DIN Sync or jack outputs and start your MIDI sequencer.

    Note that 24 and 48 ppqn lines are running all the time (if there
are incoming tick messages, of course), while other lines will start
running on Start message and end running on Stop message.