Shruthi : Problem with MIDI IN


The synthesizer works perfectly (great sound!), the problem is when I connect to “MIDI IN” to a sequencer (Roland MC808): the principle works, but when a time is locked (stop working the buttons and knobs ) and goes off. How can that be? Can be some bad component soldier?. thanks

yes, MIDI-IN works!, thanks



Keep the 6N138, and replace the 10k resistor near the optocoupler by a 220 ohm one.

I bought a 6N138. Now all the time I get a “#” character (according to the manual > invalid SYSEX data) when I connect any MIDI IN, and do not hear any notes. I tried with a sequencer (Roland MC808) and a keyboard (microkorg), and always with the same result –> “#”. What can be wrong?

This is really stupid, I know, but are you sure your Roland is outputting MIDI? Have you tested it with something else?

I have sat here dumfounded on occasion after hooking up my synths to Logic and turning Local Control to OFF. Next time I fire everything up I expect my synth to control my Shruthi and nothing happens… until I remember that I turned Local Control off… Maybe my forgetfulness will eventually help some stricken soul…

yes, I’m sure

“Shruthi midi in” <----> "midi sequencer out “, alone.I will buy the 6N138. On the internet I see many types of” 6N138 "(6N138-000E,-300E 6N138, 6N138, …), all would be valid?

You can try that, but you’d rather order a 6N138. This problem happens because: 1/ your 6N137 is too fast (their speed vary from unit to unit) and/or 2/ Your ATMega644p is too sensitive to sharp edges on the MIDI signal (bug documented here)

Trying another 6N137 might not make the problem go away. A slower opto like the 6N138 solves the problem most of the time but occasionally causes problem with some MIDI sources.

But before we’re diving into that, maybe it could be something else. How is the Shruthi connected with the sequencer? Maybe you’re creating a MIDI loop by having the Shruthi connected to the sequencer both with in > out and out> in

if I buy another 6N137 could solve the problem? may be that the chip is broken?

Try replacing the 6N137 by a 6N138.