Odp: [sdiy] MIDI specifications

[Roman Sowa]

Hi,
start and stop bits are taken care of in the hardware, whether it
is standalone UART or internal uC block, so you don't worry
about it. If you have software emulation UART, just add one low
bit at beginning, and one high after 8 data bits (LSB sent first).
Delay between bits is 32ms, not 40. together with start and
stop bit it makes 320ms between bytes.

Yes, DIN 4 and 5 form the pair. Data is sent on 5 and 4 is
tied to +5V. Don't forget about two 220ohm resistors at
those pins. Good practice is to add 2 ferrite beads or chokes
there too in series with resistors, to lower EMI.
In idle, both 4 and 5 pin are at +5V, sending low bits forces
current flow in the loop.

Roman

----- Original Message ----- 
From: Blitzcraig <blitz at nmt.edu>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, April 17, 2003 1:54 AM
Subject: [sdiy] MIDI specifications


> 
> hey all, got the code compiled for my sequencer, but I'm having troubles
> with the MIDI specifications, i.e. timing and pins.
> 
> MIDI specification says it's Asynchronous serial, baud rate is 31.25 Kbaud
> and a serial byte has 1 start bit, 8 data bits and 1 stop bit.  I
> understand how there's a status byte followed by two data bytes, but I
> don't see how it's 10 bits as described above.  Maybe I don't understand
> the concept of asynchronous serial?  As a I see it, note on will be...
> 
> status:  1001XXXX
> key:  0XXXXXXX
> velocity: 0XXXXXXX
> 
> I send this out of my microcontroller, with a 40ms delay between bits
> (MIDI spec says 320 ms per serial byte)?  Am I understanding this
> correctly?  Where does the start bit and stop bit come into play?
> 
> Second question is about MIDI port wiring, pin 1 & 3 are not used, pin 4
> and 5 are pair?  Which pin is sending the serial data?  Which pin is tied
> to my microcontroller ground, etc.
> 
> thanks for your help, I hope you could understand my amature questions.
> 
> -Joe
> 
>