[sdiy] MIDI Switch

[Andre Majorel]

On 2002-03-18 09:40 +0100, Sowa Roman wrote:

> It can be done with 2 UARTs and some logic. Connect their data buses
> in this way: 6MSBs direct, 2LSBs via OR-gates. The other input of the ORs
> are driven by rotary encoder, or any kind of switch to give 2-bit data.
> Every channel byte has MSB=1, so whenever 4 LSBs are 0s (channel 1)
> and MSB=1, you drive this switch to override midi channel to wanted
> number.

Hey, clever. But not every status byte is a channel message. You
also have to check that the top nibble is not Fh.  Perhaps a three
input nand would do ?

  b7 --------+  ___
        ___  +-|   \
  b6 --|   \   |   |--- high iff 80h <= x < F0h
  b5 --|   |o--|___/
  b4 --|___/

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
std::disclaimer ("Not speaking for my employer");