Reading single bit out of a byte (or word or long)

Litefire

hey, say i have four sensors whose pin states i want to store into a single variable (sensor).

sensor := sensor1
sensor :+ sensor2 <<1
sensor :+ sensor3 <<1
sensor :+ sensor4 <<1

now, how do i read single bits out of that sensor variable? is there a way besides simple bit shifting?

~~Brian

cgracey

You could put those bits into the VSCL register and then be able to manipulate like this:

'Output sensor1 bits 0..3 onto P0
VSCL := sensor1
outa[noparse][[/noparse]0] := VSCL[noparse][[/noparse]0]
outa[noparse][[/noparse]0] := VSCL
outa[noparse][[/noparse]0] := VSCL
outa[noparse][[/noparse]0] := VSCL

'Input P0 into sensor1[noparse][[/noparse]0..3]
VSCL[noparse][[/noparse]0] := P0
VSCL := P0
VSCL := P0
VSCL := P0
sensor1 := VSCL

That code doesn't do anything practical, but it shows how you can (ab)use VSCL for any bitwise purpose. You can specify ranges of bits to: VSCL[noparse][[/noparse]3..0] or the reverse VSCL[noparse][[/noparse]0..3].

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Chip Gracey
Parallax, Inc.

Litefire

i think you might have dropped off the [noparse][[/noparse] index] part of VSCL, but i get the idea. thanks!

i assume this would be faster than bitwise shifts... could i set VSCL as an alias to sensor? so that when sensor changes VSCL changes along with it?

~~Brian

cgracey

Woops! You're right that I forgot the index notation. You can't use this as an alias, though, only a temporary workspace.

Litefire said...
i think you might have dropped off the [noparse][[/noparse] index] part of VSCL, but i get the idea. thanks!

i assume this would be faster than bitwise shifts... could i set VSCL as an alias to sensor? so that when sensor changes VSCL changes along with it?

~~Brian

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Chip Gracey
Parallax, Inc.

Litefire

thanks chip.

~~Brian