Diodes in keyboard circuits, etc.

[The Old Crow]

On Mon, 2 Oct 2000, Synthusiast wrote:

> I wonder where these diodes that you find in keyboard circuits and matrix
> switch circuits are used for. Is it for debouncing or is it something
> totally different?

  They are there to prevent "sneak" paths from occuring when holding down
more than one key.  Without the isolating diodes, "phantom" notes might
occur as the electrical combination of the crossed rows and columns might
end up looking like other unpressed keys were down.  Not to mention,
matrix encoder lines might get into hi/lo fights and damage chips.

Crow

/**/