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Raspberry Pi MiniPIIO MIDI board

June 26th, 2014

We designed our first Pi MIDI interface way back in 2012 while we were waiting for our first Pi board to arrive.

It’s went through several revisions since then and now looks like this:

RPi_MiniPiio_MIDI_small

RPi_MiniPiio_MIDI_Front_small

The circuit is now completely 5V as per the original MIDI specification but the MIDI IN is 3.3V compatible with the Pi via a voltage divider circuit.

OK that’s the hardware what about the software?

Getting a MIDI 31250 Baud Rate on a Pi is not easy as it should be as 31250 is not a standard Pi baud-rate. But you can trick your Pi into it if you overclock (or rather underclock) the UART clock.

Start a terminal session and type:

[sourcecode]
sudo nano /boot/config.txt
[/sourcecode]

Add these lines to the end of the file

[sourcecode]
# Change UART clock to 2441406 for MIDI 31250 baud rate

init_uart_clock=2441406
init_uart_baud=38400
[/sourcecode]

save and exit.

Once saved reboot your Pi.

Next we need to stop the serial UART being used by Raspbian for the shell console. Check my previous post “MiniPIiio RS232 set-up” on how to do this.

Finally we need to add the following to “cmdline.txt”

[sourcecode]
bcm2708.uart_clock=3000000
[/sourcecode]

After doing all of this we should be ready to connect a MIDI keyboard or synth to our Pi.

 

Check our store on Tindie:

https://www.tindie.com/stores/DTronixs/

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