[PD] Sending Startbit and Stopbit with comport for MIDI with Arduino

[Martin Peach]

Hi Ingo,
It's not clear to me which parts of your setup are hardware MIDI and
which are hardware serial, so this may be not relevant:
MIDI uses the same serial protocol as regular serial, the difference
is the baud rate (31250 is not a standard baud rate)
At the hardware level, MIDI is optoisolated and works as a current loop.
At the Pd end, MIDI messages are handled completely separately from
whatever [comport] is doing, so you have to 'manually' reconstruct
MIDI from a serial stream (as with [midifile], which also doesn't
integrate with Pd's MIDI sytsem, as MIDI is being handled at the
driver level, and uses a different software interface).

So if your baud rate on the Arduino is 31250, at the minimum you need
[comport] to be running at 31250 s well, which is not usually
possible.
It's easier to use a MIDI interface on the computer and send MIDI from
the arduino directly. This can be done using 2 220 Ohm resistors and a
DIN-5 connector.

Martin






On Mon, Mar 22, 2021 at 4:13 AM Ingo <ingo at miamiwave.com> wrote:
>
> Hi,
>
> I would like to send MIDI with [comport] from Pd by using an Arduino.
>
> Reading into Pd is no problem.
> It also works fine as a MIDI Thru by simply forwarding the Serial1 RX input
> (MIDI input) to the Serial1 TX output (MIDI Thru).
> Something like this:
>
>       if (Serial1.available() > 0) {
>         Serial1.write(Serial1.read());
>       }
>
> (The loop duration is only about 250 盜 so there is no timing problem in
> this case.
> For data coming in faster than the loop duration I would probably have to
> read into an arry first.)
>
>
> However, if I'm sending a MIDI message from Pd it's not recognized by the
> connected MIDI interface.
> I'm assuming that's probably because there is no startbit and stopbit that
> the MIDI interface is looking for.
>
> According to the helpfile I can send a stopbit with [comport] but I didn't
> find anything about a startbit.
>
> Is there a possibility within Pd and [comport] to send a startbit or would
> it make more sense to add the startbit and stopbit within the Arduino
> programming?
>
> Thanks!
> Ingo
>
>
>
>
>
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