Re: Delphi MIDI Programming, nibble

Posted by webmaster Guido on March 25, 2003 at 02:22:00:

In Reply to: MIDI Programming posted by Kevin + Mullzo on March 24, 19103 at 14:45:36:

: I am writing a program for my current university course
: and need help. I am developing a midi thru program which responds to incoming messages and records values in edit boxes, spin edits and scrollbars. I have everything completed ie Pitch Bend messages, velocity messages and Midi I/O controls, the one thing can't figure out is how to record incoming channel changes
: as the channel change message is on the second nibble of the status byte and I don't know how to isolate it.
: Please help!!!
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In the examples below, the dollar-sign prefix indicates hexadecimal notation.

You can logically AND a byte with a mask-byte that contains zero's at the positions that you are not interested in. As you know, bytes are from $00 (0 in decimal, 00000000 in binary) to $FF (255 decimal, 11111111 binary).

So if you AND with $0F, you obtain the four lowest bits (low nibble), while AND-ing with $F0 isolates the four highest bits (high nibble). Examples of Delphi functions to return high- and low order "nibbles":

function LowNibble(B: byte): byte;
begin
  Result := B AND $0F;
end;
 
function HighNibble(B: byte): byte;
begin
  Result := B AND $F0;
end;

Regards,
webmaster Guido