On Tue, 3 Sep 2019 07:39:14 -0400, "J.B. Wood" 
declaimed the following:

>Hello, all.  Just thought I'd revisit this topic since it's been a
>while.  Has anyone ever constructed a Pi-based standalone 1-2 channel
>MIDI sequencer?  By standalone I mean it has an integral display and
>required pushbuttons/rotary knob for device control.
>
 What do you intend to show on the display?

 What type of control do you envision? (If you visualize a one/two
octave keyboard, you then have to specify how many notes in parallel -- one
note at a time can use a simple row/column keyboard scan -- but when you go
beyond two notes such a matrix can generate ghost key presses; avoiding
ghosts requires a linear matrix, which means LOTS of GPIOs -- a 1x24 would
need 24 GPIOs to detect key presses, while a 4x4 is only using 8 GPIOs for
16 keys)

>I'm not talking about a DAW, just a small box with appropriate
>interfaces (DIN in/out and/or USB (for MIDI-over-USB)) that allows one
>to both record in real-time, store on a flash drive and/or micro SD in
>.MID format (type 1 or 2) and play back?  This functionality is readily
>available on Linux OSs (but you need a USB-to-MIDI interface such as an
>M-Audio MIDISPORT).  The device I would like to functionally duplicate
>can be seen in action at https://www.youtube.com/watch?v=5L6oicVUcvQ
>

 MIDI itself is just an odd (and these days slow -- 31.25kbps) serial
port using 8N1 content, using opto-isolators on the receive lines (cf: this
Arduino shield https://www.sparkfun.com/products/12898 ). Using a suitable
ribbon cable might allow connecting this to an R-Pi (however -- you might
need level-shifters on the serial port; Arduino shields are commonly 5V
systems, the R-Pi is 3.3V; and the potentiometers won't be useful as the
R-Pi does not have ADC inputs)

 Timing is not part of the protocol -- timestamping on record, and
delaying on playback, is up to the processor handling the data stream.


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

--- SoupGate-Win32 v1.05