The MIDI Forum

Recent
Categories
Tags
Users
Badges
View Replies (10)

Resolved 3.3V vs 5V and what resistors to use?

  1. Technical Question
1
Votes
Undo
  1. Alex
    Alex
  3. MIDI Connections
  4. Wednesday, 24 August 2016
  5.  Subscribe via email
I'm developing a project on a board that uses 3.3V. And there has to be just one MIDI out. I tried connecting ground, vcc and data pins to a midi jack and it works fine with Kemper profiling amp. I tried it without any resistors as well as 220 ohm and 100 ohm on the 3.3V power pin (vcc) and there was no difference.
Is it better to use 5V than 3.3V?
What resistors are needed for each case and why?

Thank you!
Comment
There are no comments made yet.
Responses (10)
Clemens Ladisch
Clemens Ladisch
Sherlock Holmes The Voice
Accepted Answer Pending Moderation
0
Votes
Undo
The Electrical Specification Update (PDF) shows what resistors to use if the output is powered with 3.3 V.

MIDI requires a current of at least (and not much larger than) 5 mA. Resistors of 10 Ω and 33 Ω are recommended to achieve this with 3.3 V; your device might work with other values, but there is no guarantee that this works with other devices.
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 1
Alex
Alex
Accepted Answer Pending Moderation
0
Votes
Undo
Clemens Ladisch wrote:

The Electrical Specification Update (PDF) shows what resistors to use if the output is powered with 3.3 V.

MIDI requires a current of at least (and not much larger than) 5 mA. Resistors of 10 Ω and 33 Ω are recommended to achieve this with 3.3 V; your device might work with other values, but there is no guarantee that this works with other devices.


Thanks! If the current should be around 5mA, why is it not 660 ohms (3.3/0.005 according to ohms law)? 3.3/10 gives 330 mA and 3.3/33 gives 100 mA.
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 2
Alex
Alex
Accepted Answer Pending Moderation
0
Votes
Undo
Clemens Ladisch wrote:

The Electrical Specification Update (PDF) shows what resistors to use if the output is powered with 3.3 V.

MIDI requires a current of at least (and not much larger than) 5 mA. Resistors of 10 Ω and 33 Ω are recommended to achieve this with 3.3 V; your device might work with other values, but there is no guarantee that this works with other devices.


Thanks! If the current should be around 5mA, why is it not 660 ohms (3.3/0.005 according to ohms law)? 3.3/10 gives 330 mA and 3.3/33 gives 100 mA.
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 3
Clemens Ladisch
Clemens Ladisch
Sherlock Holmes The Voice
Accepted Answer Pending Moderation
0
Votes
Undo
This is not the correct way to compute the current; you have to add up the voltage drops of all three resistors (the output's two, and the receiver's 220 Ω one) and the optocoupler's LED. (See the specification.)
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 4
Alex
Alex
Accepted Answer Pending Moderation
0
Votes
Undo
Clemens Ladisch wrote:

This is not the correct way to compute the current; you have to add up the voltage drops of all three resistors (the output's two, and the receiver's 220 Ω one) and the optocoupler's LED. (See the specification.)

Thank you, found it in the specification :)
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 5
tim
tim
Accepted Answer Pending Moderation
0
Votes
Undo
What happens if a 5V midi device is connected to a 3.3 volt midi device?
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 6
tim
tim
Accepted Answer Pending Moderation
0
Votes
Undo
I am expecting to measure 5mA of current drawn between two devices, however it is much less than that, about 0.1 mA. But things seem to be working ok. I have the current meter in series with the 5 volt line, and later in series with the MIDI data, but there is much less than 5mA. Is that correct?
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 7
Clemens Ladisch
Clemens Ladisch
Sherlock Holmes The Voice
Accepted Answer Pending Moderation
0
Votes
Undo
A MIDI line is idle most of the time, so the average current is not 2.5 mA, but approximately zero.

To measure the current during a zero bit, you need a faster device, such as an oscilloscope.
Comment
There are no comments made yet.
  1. more than a month ago
  2. MIDI Connections
  3. # 8
Roberto
Roberto
Accepted Answer Pending Moderation
0
Votes
Undo
Clemens Ladisch wrote:

This is not the correct way to compute the current; you have to add up the voltage drops of all three resistors (the output's two, and the receiver's 220 Ω one) and the optocoupler's LED. (See the specification.)

Thank you, found it in the specification :)


Hello
I have same problem...connecting midi device to 3.3v (Arduino MKR 1010).
What is the correct schematic for this connection ?
All the schematic I've found says only 220ohm resistors...but output signal is unable to talk to some devices..
Please help
Roberto
Comment
There are no comments made yet.
  1. 2 weeks ago
  2. MIDI Connections
  3. # 9
Clemens Ladisch
Clemens Ladisch
Sherlock Holmes The Voice
Accepted Answer Pending Moderation
0
Votes
Undo
Are you using a MIDI output, or a MIDI input, or both?

A 3.3 V MIDI output must use different resistors (see the Electrical Specification linked above). A 3.3 V MIDI input does not need to change anything.
Comment
There are no comments made yet.
  1. 2 weeks ago
  2. MIDI Connections
  3. # 10
  • Page :
  • 1


There are no replies made for this post yet.
Be one of the first to reply to this post!
About the MIDI Association
MIDI Association IP Policy
MIDI Association Anti-Trust Policy

Contact Us

© 2020 The MIDI Association