MIDI Output (Via USB or MIDI)

RubrChicken

Good evening propeller forums!

I was working with some (free trial ) DJ software that had midi control. I wanted to use a few common buttons such as play and sync without the oh-so-cumbersome action of using the mouse, so I thought of a midi controller. I hooked up a midi keyboard, and it worked fine. Then I thought, why not have a dedicated box for this? So... Off the OBEX. I found two MIDI in objects, but no MIDI out objects! Is there a way to send MIDI messages to a computer over the prop's USB connection? If not, I can go out and buy a MIDI plug, and use that. The keyboard has a MIDI in, so I could send signals through that. I know what midi messages I want to send, I want to be able to configure the device easily to any message. I have no problem with the button push thing, but how do I A)Send MIDI messages and B)Have the propeller identify itself as a midi device?

I believe midi data looks something like this:

F0 7F 7F 06 01 F7

Thanks!

phishguy

MIDI is a serial protocol of 8 bits, 1 start bit, 1 stop bit, and no parity at 31250 baud. It is also an optoisolated interface. Therefore, with an optoisolator, and a couple of resistors, you should be able to make a midi out and in. Then you can just use the Full Duplex Serial object for sending and receiving MIDI sequences.

See this site for reference. It has a schematic of a Rs232/MIDI converter. You wouldn't need the MAX232 as you would be using IO pin levels.

www.compuphase.com/electronics/midi_rs232.htm

Oldbitcollector (Jeff)

Do you mean something like I was in my piano style midi player?
Based on Andy's "MIDI Expander" so you'll need to install the Roland Driver from
tomscarff.110mb.com/USB_MIDI/USB_MIDI.htm

OBC

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Ariba

Attached is a Schematic of the most simple MIDI Out curcuit.
The difference to the normal 5V circuit is the missing resistor at +3,3V, so this pin is not
short circuit proof.

As phisguy described, you can use the FullDuplexSerial driver with 31250 Baud, to send MIDI Bytes.

Andy

Wurlitzer

If you do not want to use the Full Duplex Serial object, this is the PASM code I have been using to send MIDI data to both a PC and my MIDI equipped pipe chamber.

Prior to calling "SendDataBits" tmp2 must = 8 for 8 databits and "NumBytesToSend" must be set to the number of bytes in the message as they are not all 3 byte messages. NOTE: My data has the Bytes in reverse order from how they must be sent hence the "rol MIDI_PipeMsg, #16" statement which just gets the proper byte in position to send.

There is no need to "Identify" the prop as a MIDI device.

This has been rock solid code while it could be cleaned up a bit I will most likely leave it alone.

EDIT: NOTE: I use a 2N2222 to buffer the output from the Prop and that has worked well over 50' of cable from the console to the pipe chamber. If you don't use such a buffer then you should use MUXC instead of MUXNC to invert the output.

SendMIDI  'Upon entering, DIRA for 2 Midi output pins must be set appropriately                                     '   
                        mov     tmp2, #8        '8 data bits
                        mov     tmp1, #0         wz      ' all this does is set the zero flag
                        muxz    outa, midiOutPipe       'send Start Bit for pipe chamber if DIRA is enabled
SendDataBits                
                        call    #BaudDelay  'waits the appropriate time based upon selected baudrate
                        ror     MIDI_PipeMsg,#1 wc  'the carry bit reflects the status of the LSbit
                        muxnc    outa, midiOutPipe
                        djnz    tmp2, #SendDataBits  wz                        
                        'now send stop bits
                        call    #BaudDelay   'waits the appropriate time based upon selected baudrate
                        mov     tmp1, #0 wz      ' all this does is set the zero flag                             
                        muxnz    outa, midiOutPipe       'send Stop Bit for pipe chamber if DIRA is enabled
                        call    #BaudDelay    'waits the appropriate time based upon selected baudrate
                        rol     MIDI_PipeMsg, #16 'shift byte just sent then 1 byte more. Next databyte=LSByte
                        djnz    NumBytesToSend, #SendMidi'number of bytes must be set prior to call SendMIDI                        
SendMIDI_ret            ret                        
'===============================================================================
'===============================================================================
BaudDelay               mov     bitClk,cnt    
                        add     bitClk,bitticks
                        waitcnt bitClk,bitticks
BaudDelay_ret           ret

...blah, blah, other code

bitticks                long 2560'  2560-8cpu cycles for BaudDelay Call and Return. One bit width = clkfreq / 31,250

Post Edited (Wurlitzer) : 12/7/2009 2:17:20 PM GMT

garylake

Hi, this sound good but how to use it? What spin code would I uase and what parameters do you set up for the SendMidi, what data do I need? I want to send a midi note (say 60 middle C), velocity, and channel.