Grumpenspiel MIDI Circuit Reference
This page is a reference for MIDI IN, OUT, and THRU circuits. Additionally, it includes Power Thru compatibility.
|Pin||MIDI OUT||MIDI IN||Power Thru|
|4||VCC through Ra 220 resistor||Opto-Isolator pin 2 through Rb 220 resistor|
|5||UART signal||Opto-Isolator pin 3|
MIDI OUT (no Power Thru)
NOTE: Grumpenspiel MIDI controllers (i.e. MIDI OUT) omit the optional Rc 220 resistor on the signal pin (pin 5).
MIDI OUT (with Power Thru)
MIDI IN (no Power Thru)
NOTE: Rb is the current limiting resistor for the opto-isolator LED. The MIDI spec image has the opto-isolator LED oriented opposite from the Eagle schematic for 6N138. MIDI pin 5 (signal) connects to opto-isolator pin 3. MIDI pin 4 (VCC) connects to opto-isolator pin 2 through Rb 220 resistor.
MIDI IN (with Power Thru)
MIDI THRU (no Power Thru)
NOTE: Grumpenspiel synths do not pass the IN signal to a THRU output. This schematic is included for reference only.
MIDI THRU (with Power Thru)
No sample circuit for this configuration. Grumpenspiel synths use MIDI IN only. MIDI THRU is accomplished on Power Thru only. PT splits the MIDI signal out to all the instruments directly using hex Schmitt inverters.