From Robin Whittle Sent Thu, Nov 27th 2003, 00:32
From Robin Whittle Sent Thu, Nov 27th 2003, 00:32
It really doesn't matter how you make the electrical connections. The Run/Stop (pin 1) and Clock (pin 3) are robust signals - 5 to 15 volts - with no special fussiness with capacitance, shielding etc. You could probably run them a kilometre or more on unshielded cables and it would be fine. Beware the pin numbering of 5 pin DIN connectors. At one end is pin 1, and at the other pin 3. In the middle is pin 2. That was for the 3 pin arrangement. A 5 pin DIN plug has the same numbering for those pins, but adds pins 4 and 5 in between. Some Roland gear receives signals on these these pins - for instance the TB-303 and TR-808 receives Tap on pin 4 and an some undocumented function on pin 5 - the circuit diagram has a blank for the label of this pin. But these are not necessary for starting, stopping and running in sync. The TR-606 is the same, but it also sends Tap on pin 4 - an approximately 5 volt signal (6 volts via a diode). There's no resistor in this circuit, so if pin 4 was shorted to ground, then pressing the Tap button would cause excessive current to flow through the diode. You could get some existing leads - including any MIDI lead which has wires for all 5 pins - as someone suggested, and cut off the connectors at one end, or cut them in half, and solder all the common wires together at one point. That would be an octopus or star structure. The only thing to beware of is that some old audio leads for connecting stereos had the pin 1 and 4 of one end connected to the pin 3 and 5 of the other - to automatically connect the two output channels of one device to the inputs of the other. My suggestion of a daisy chain is to use three different coloured pieces of hookup wire into connector A, with the other end of those wires going to connector B, together with a second set of three wires which goes to connector C etc. The Run/Stop signal goes high at the start of the song and low when the song is not playing. The Clock signal is a square wave, 24 pulses per quarter note. It can be running when the Run/Stop is low too - just to make the slave device's lights blink. However, ideally, the Clock signal should be brought low before the Run/Stop rises at the start of a song, which can lead to arbitrarily short Clock signals, because there's no telling when the song will be manually started. Unfortunately there's no technical specification on the timing of Roland (AKA DIN) Synch. As far as I know, there's no spec on the minimum width of the clock pulse, or even the voltages which must be used. For instance, its a bad idea to send the first Clock pulse (its positive edge) too soon after the rising edge or the Run/Stop - because particular slave devices, such as a TB-303 or TR-808 won't have got their act together after the Run/Stop activation before the Clock pulse arrives, so they will miss that, and actually start their sequence on the second Clock pulse. This is something which should be born in mind by all people who create MIDI to Sync converters. How long is "too soon"? There's no spec - but its best to try it on a TB-303 or similar and then add quite a large margin for Justin (just in case). This means writing software in the device to count up potentially several MIDI clock codes which might arrive faster than they can be sent out to the Roland Synch device - and then catching up with them by sending Clock pulses at some reasonable (whatever that means) rate, involving some limit on how short the pulse can be, and how short the delay until the next one. http://www.firstpr.com.au/rwi/dfish/ Devil Fish mods for the TB-303