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mi_dach
Joined: Dec 17, 2005 Posts: 133 Location: Sweden
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Posted: Wed Aug 02, 2006 11:47 am Post subject:
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Blue Hell wrote: | mi_dach wrote: | Or do I have it backwards, and the Thru is a copy of the out port?.. |
A copy of the input I think, directly in hardware and not routed through the processor. The MIDI standard used to have schematic hints for this.
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My bad for not studying the specifications too closely I was perhaps thinking more like a MIDI merge then, two inputs being joined into one output. I don't have enough gear at the moment to require the use of a Thru port, but it definitely seems useful for later, thanks for setting me straight. |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24075 Location: The Netherlands, Enschede
Audio files: 277
G2 patch files: 320
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Posted: Wed Aug 02, 2006 11:57 am Post subject:
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Found a schematic example at : http://www.borg.com/~jglatt/tech/midispec/hardware.htm
This seems quite like the "original" to me, even the remarks about the opto isolator seem familliar, but probably its not as bad with modern devices as it was 20 years ago. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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jksuperstar
Joined: Aug 20, 2004 Posts: 2503 Location: Denver
Audio files: 1
G2 patch files: 18
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Posted: Wed Aug 02, 2006 12:28 pm Post subject:
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Despite the fact that it's not "MIDI Spec Compliant", I like the soft-thru that's offered in most devices today. Since I have everything going in & out of the PC anyway, this function would've had to be done eventually anyway, and it allows me to daisy chain my devices without a need for a bunch of merging at the end. I highly recommend this method on top of the basic thru. |
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State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Thu Aug 03, 2006 7:19 am Post subject:
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Quote: | Despite the fact that it's not "MIDI Spec Compliant", I like the soft-thru that's offered in most devices today. Since I have everything going in & out of the PC anyway, this function would've had to be done eventually anyway, and it allows me to daisy chain my devices without a need for a bunch of merging at the end. I highly recommend this method on top of the basic thru. |
The "soft" thru also adds a capability to filter or strip off unwanted MIDI data before it's passed onto the next device. Something the hardware thru is not able to do. You can do data "thinning" also so as to not tax the MIDI devices downstream. Using an AVR, the MIDI data latency is so low when using interrupt driven I/O software approach that it would behave very similar to the pure HW solution in terms of delay. Best case delay performance though is (320 uS + Interrupt Service Overhead). The 320 uS is equal to 10 bit times and is rather neglagable. The ISR overhead is the critical specification here and should be written "real time enough".
Bill |
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State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Thu Aug 03, 2006 7:27 am Post subject:
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Quote: | This seems quite like the "original" to me, even the remarks about the opto isolator seem familliar, but probably its not as bad with modern devices as it was 20 years ago. |
Yes, Jan. I usually use the 6N139 or 6N138 optocouplers. The inverters I use a usually 74HC04 type. To speed the circuit up a bit and lower latency, you can lower the optocoupler collector resistor to a range of 150-180 ohms. To high a value tends to "slew" the voltage too much.
Bill |
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Navicat
Joined: Apr 02, 2015 Posts: 4 Location: Greece
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Posted: Tue Apr 07, 2015 8:14 am Post subject:
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Hey that's what i need..Midi to 16 CV and 16 gates!!!
Is this alive??
Best Regards
Tilemachos |
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