From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailrelay005.isp.belgacom.be (mailrelay005.isp.belgacom.be [195.238.6.171]) by ozlabs.org (Postfix) with ESMTP id DD8B0DDF5D for ; Mon, 13 Oct 2008 22:04:43 +1100 (EST) From: Laurent Pinchart To: "Leon Woestenberg" Subject: Re: Floating inputs on unused GPIO pins Date: Mon, 13 Oct 2008 13:04:41 +0200 References: <200810131156.59477.laurentp@cse-semaphore.com> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1296436.mzcYet2qAg"; protocol="application/pgp-signature"; micalg=pgp-sha1 Message-Id: <200810131304.41435.laurentp@cse-semaphore.com> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --nextPart1296436.mzcYet2qAg Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Hi Leon, On Monday 13 October 2008, Leon Woestenberg wrote: > Hello Laurent, >=20 > On Mon, Oct 13, 2008 at 11:56 AM, Laurent Pinchart > wrote: > > our hardware engineer asked me to make sure all unused GPIO pins are > > configured as outputs to avoid floating inputs. He got theory on his si= de > > (floating inputs can lead to higher current consumption, metastability = or > > even permanent damage), but I'd like to ask the list for practical > > feedback. =20 > > > Ideally, configure them as inputs or tri-state (both mean high > impedance), and do use pull-down or -up resistors. As I explained in my mail to Geert, that's not really an option. The GPIO p= ins are connected to an optional expansion module. When the module is plugg= ed in the pins have dedicated functions. When the module is not present the= y are by default floating inputs. That's the case our hardware engineer is = concerned about. > Now, the answer might be different when your pins are not connected. > Check on the processor if internal pull resistors are present. If so, > use as input. If not, then your h/w engineer *may* have a point, not > sure on that though. There are no internal pull-up or pull-down resistors on the MPC8248 GPIO pi= ns. I know our hardware engineer has a valid point theoretically. Does the = point stand practically, or does the MPC8248 "state-of-the-art"(tm)(c)(what= ever) technology make floating inputs safe ? =2D-=20 Laurent Pinchart CSE Semaphore Belgium Chaussee de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 =46 +32 (2) 387 42 75 --nextPart1296436.mzcYet2qAg Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEABECAAYFAkjzK0kACgkQ8y9gWxC9vpeNgQCg3rWmoJjnooykfi8m8aZSRqig FpoAoLGzVClm6F8lesGvwKaeszolEHC1 =fP1L -----END PGP SIGNATURE----- --nextPart1296436.mzcYet2qAg--