Alyseum ALeX User Manual
Page 7
ALeX – User’s manual © - Revision 1.7
Page 7
4.4.4
How to find the solder points for the MIDI In
The MIDI standard mandates the use of an opto-isolator. This eases finding the MIDI-in
signal that the ALeX requires.
The MIDI-in signal going to the ALeX is to be connected to the output of the opto-isolator.
Moreover, the majority of opto-isolators require a pull-up resistor at their output.
Depending of the ease of access connect the green wire to either the output or the pull-up
resistor.
Refer to the datasheet of the opto-isolator manufacturer to find the output pin.
For proper operation of the ALeX, the signal flow between the opto-isolator output and the
processing unit of your equipment MUST be cut.
This requires cutting a copper trace or, more rarely, a wire inside your equipment.
Using a Ohmmeter to check the continuity, locate where a cut can be made that does not
interfere with the pull-up resistor that must remain connected with the output of the opto-
isolator.
When cutting a copper trace on a printed circuit board, be extremely careful as to not cut
nearby traces.
Proceed progressively until the continuity test proves that the cut is effective.
The red wire is to be soldered on the side of the trace now disconnected from the circuit
where the green cable is connected.
This is likely the most delicate soldering job as there might be no components to solder the
red cable besides the micro controller of the equipment.
It is therefore recommended to connect the red wire directly to the copper on the board.
This requires scratching the insulation layer until a reasonable length of copper is accessible.
4.4.5
How to find the solder points for the MIDI Out
The best place is the resistor that leads to the pin 5 of the DIN connector.
Connect the yellow wire to the side of the resistor opposed the one going to the connector.
In installations with two MIDI outputs, proceed similarly with the orange wire and the second
MIDI out connector.
4.4.6
Schematic for 1 MIDI In and 1 MIDI Out
MIDI In
MIDI Out
Opto
App.
UART
R
LK/ACT
ALYSEUM
ALeX
App.
Power
5V to 18V
GND or 0V