Log in
Register

  • The MIDI Messages Forum  Ask and you shall receive

    The MIDI Messages Forum
    Ask and you shall receive

  1. Zach
  2. MIDI Connections
  3. Wednesday, 16 November 2016
  4.  Subscribe via email
Hi,

I'm new to MIDI, so this question may seem a little "noobish." I am trying to connect a keyboard to a 3.3V board using MIDI. I see in the MIDI DIN Electrical Specification that MIDI didn't always allow 3.3V, so I assume that there may have been an important hardware change with that. Do I need to use a newer keyboard or cable to correctly setup the connection, or do I only worry about using the resistor values and such as described in the specification?

Thanks
Comment
There are no comments made yet.
Accepted Answer
Clemens Ladisch Accepted Answer Pending Moderation
1
Votes
Undo
The MIDI specification specifies a 5 mA current loop, and shows three 220 Ω resistors to limit the current when used with a 5 V transmitter.
When you have a 3.3 V transmitter, the two resistors in the transmitter must be smaller to get the same current, as shown in the Electrical Specification Update.

The receiver does not need to know what voltage the transmitter uses; it always uses the same 220 Ω resistor. All transmitters are designed to work with that same receiver circuit. This means that all transmitters and receivers are compatible.

(The receiver can use either 5 V or 3.3 V as supply for the optoisolator; this part of the circuit is isolated from the current loop, and does not affect compatibility of the MIDI interface. But note that only the PC900/H11L1 optoisolators can run at 3.3 V; other common models like the 6N137 or 6N138 require 5 V.)
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # Permalink
Zach Accepted Answer Pending Moderation
0
Votes
Undo
Thank you very much. That exactly answers my question!
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 1
  • Page :
  • 1


There are no replies made for this post yet.
However, you are not allowed to reply to this post.