From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Sat,  2 Jan 2016 10:06:31 -0800
To: blstuart@bellsouth.net, 9fans@9fans.net, quanstro@quanstro.net
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Subject: Re: [9fans] Pi updates
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On Fri Jan  1 21:15:03 PST 2016, blstuart@bellsouth.net wrote:
> On Fri, 1/1/16, erik quanstrom <quanstro@quanstro.net> wrote:
> > i'm looking @ the gpio interface, and i wonder what the recommended
> > technique for sampling a pin might be from a shell script?
>=20
> I haven't really used it in shell scripts, but if I were going to do
> so, I'd probably write up a little utility to take a hex string and
> a bit number and do the 'and' on it.  Then feed that with the
> result of dd to get exactly one sample from devgpio.  On the
> other hand, if one of the usual suspects (e.g. hoc, bc, dc, awk)
> have some bit-wise operators I'm forgetting, use that.

the (atom) aux/number program does do that; none of the others do
for fairly fundamental reasons: as awk and hoc are really floating
point, and bc and dc are mp, and the mp library has no bit operations.
i believe acid can as well, but only with great pain.

perhaps just using base 2 for the encoding would make life a lot easer. s=
o=20

00000000000000000000000000010000000000000000000000000000000000000

for bit 27 active.  with this format there's no limit to the number of bi=
ts one
could represent.

also, mightn't there be some value in presenting the full state of the de=
vice
to allow it to be restored directly from the status file, so perhaps 3 li=
nes
could be added, one each for up/down/float settings?

00000000000000000000000000010000000000000000000000000000000000000
00000000000000000000000000010000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000

might represent bit 27 set, with the pull up resistor active.  (perhaps
float =E2=89=A1 (pullup | pulldown) =3D=3D 0? and could be elimitated.

i'm sure a little tinkering with this idea can make it a lot more useful.

- erik