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MIDI Hardware
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Topic starter
I'm producing Midi-Signals through a microcontroller output (5V TTL), which goes into the TTL input of a SAM2695 Midi board.
To assure or control what really is going over the line or arrives at the controller, I would like to sense the signal with a probe connected to the signal and leading into my Mac computer where a program like "pocketmidi" is running. (Anyone knowinga better program, which possibly interprets the hex bytes into corresponding Midi commands?). But in the first place I would like to know what the best method is to adapt the electrical levels accordingly.
Posted : 05/04/2023 12:07 am
The standard circuit uses an NPN or a logic output with 2× 220 Ω.
Using a PNP as a voltage follower is unusual, but will work. The resistors are too small (i.e., the current is too high); use 100 Ω at pin 5 and 220 Ω at pin 4.
Posted : 05/04/2023 9:57 am
Topic starter
[quotePost id=18200]The standard circuit uses an NPN or a logic output with 2× 220 Ω.
Using a PNP as a voltage follower is unusual, but will work. The resistors are too small (i.e., the current is too high); use 100 Ω at pin 5 and 220 Ω at pin 4.[/quotePost]
Thanks. Though the circuit is taken directly from the service manual of a musical instrument. Hammond XK1. The same circuit in another Hammond manual uses 220 Ohms from +5V and 120 Ohm to the emitter. Maybe that was an error.
Posted : 06/04/2023 6:51 am
The XK1 uses a 3.3 V supply. At that voltage, 120 Ω + 22 Ω actually is too much. And the inputs always should use 220 Ω. (The noise filtering is fine, though.)
Posted : 06/04/2023 8:56 am
