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Forum Index : Microcontroller and PC projects : Duinomite (or ColorMaximite) & Midi

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hitsware
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Joined: 23/11/2012
Location: United States
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Posted: 02:10am 16 Jul 2013

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I just got 1 of these:

http://shop.moderndevice.com/products/fluxamasynth

The midi com standard says:
32.25 kbps
1 start bit
1 stop bit

I can't figure how to get the start and stop bits ?
The Duinomite will do the 32.25K but the manual
(OPEN COM) doesn't mention # of bits or start or stop
The ColorMaximite manual says the com is 8 data bits,
no parity, 1 stop bit (only speed adjustable)

Thanks for any insight ....

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 3674

Posted: 08:33am 16 Jul 2013

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Chances are it's always 1 start bit and will actually be 1 stop bit.

Try it :)

I suppose you could look at the C code to see what it does...

John

hitsware
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Location: United States
Posts: 535

Posted: 11:18am 16 Jul 2013

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Thanks .... Yea, looks like maybe the default settings are right.
(though I'm not positive)
Can't get a squeek though :(

" For 8-N-1 encoding, only 80% of the bits are available for data
(for every eight bits of data, ten bits are sent over the serial
link � one start bit, the eight data bits, and the one stop bit)."

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
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Posted: 11:21am 16 Jul 2013

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You might need to invert the signal.

Microblocks. Build with logic.

JTR0701
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Joined: 10/07/2013
Location: Australia
Posts: 71

Posted: 12:15pm 16 Jul 2013

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I think you will find that MIDI is 31.25kb/S and not 32.25kb/S. The start and stop bit are added by the PIC32 hardware UART and unless MMBasic provides an option for TWO stop bits then all the defaults are OK.

As TZ points out you do need to be more concerned about compatible physical interfacing with your module, particularly with the polarity and voltage levels of the MIDI signal. The data sheet for the module should have this information.

hitsware
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Joined: 23/11/2012
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Posts: 535

Posted: 01:30pm 16 Jul 2013

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> I think you will find that MIDI is 31.25kb/S and not 32.25kb/S.

Right. Senior moments.

>The start and stop bit are added by the PIC32 hardware UART
>and unless MMBasic provides an option for TWO stop bits then
>all the defaults are OK.

I hope so.

>As TZ points out you do need to be more concerned about compatible
>physical interfacing with your module, particularly with the polarity
>and voltage levels of the MIDI signal. The data sheet for the module
>should have this information.

I'm pretty sure I'm good there. The synth normally goes on an Arduino
board and snaps right on to the DuinoMite. Feeding it random numbers
should get some noise if even the data was inverted but doesn't ... Edited by hitsware 2013-07-17

JTR0701
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Joined: 10/07/2013
Location: Australia
Posts: 71

Posted: 01:35pm 16 Jul 2013

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hitsware said Feeding it random numbers
should get some noise if even the data was inverted but doesn't ...

No! The start and stop bits would also be inverted. What you will get is framing errors on the MIDI module, not random sounds.

hitsware
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Joined: 23/11/2012
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Posted: 04:26pm 16 Jul 2013

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JTR0701 said

hitsware said Feeding it random numbers
should get some noise if even the data was inverted but doesn't ...

No! The start and stop bits would also be inverted. What you will get is framing errors on the MIDI module, not random sounds.

I thought the 'start and stop bits' were automatic from the urt
(independent of the data) ????

JohnS
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Joined: 18/11/2011
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Posted: 08:01pm 16 Jul 2013

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Yes, automatic but if they're inverted then you'll need to correct (reinvert) them.

Do check the volts, too, as the PIC32 is a 3.3V device and maybe your Arduino is 5V?

JohnEdited by JohnS 2013-07-18

hitsware
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Posted: 05:36am 17 Jul 2013

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Volts are OK
12V up from to Fluxamasynth 'shield' from DuinoMite
Onboard 3.3V regulator, so synthchip is 3.3V
Data coming up is 3.3V pulsetrain
I need to look close at the chips data sheet.
Maybe there is an initialization code or ????

hitsware
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Posted: 10:20am 18 Jul 2013

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Problem Solved !

http://www.thebackshed.com/forum/forum_posts.asp?TID=5938&PN =1&TPN=1

JohnS
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Posted: 10:59am 18 Jul 2013

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Excellent!

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