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 EC523DDEEF for ; Mon, 13 Oct 2008 22:00:46 +1100 (EST) From: Laurent Pinchart To: Geert Uytterhoeven Subject: Re: Floating inputs on unused GPIO pins Date: Mon, 13 Oct 2008 13:00:40 +0200 References: <200810131156.59477.laurentp@cse-semaphore.com> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2564495.D8XtkFrj95"; protocol="application/pgp-signature"; micalg=pgp-sha1 Message-Id: <200810131300.43207.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: , --nextPart2564495.D8XtkFrj95 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Hi Geert, On Monday 13 October 2008, Geert Uytterhoeven wrote: > On Mon, 13 Oct 2008, 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 > >=20 > > I haven't been able to find any mention of floating input protection in > > the MPC8248 documents. Has anyone here experienced issues with floating > > inputs in real-life designs ? Do you setup your board with all unused G= PIO > > pins configured as outputs ? =20 >=20 > I always thought configurable GPIO pins default to _inputs_ after power-o= n, > so it's safe to tie them to VCC through a pull-up resistor? > For CMOS, you can tie them to VDD or GND without a resistor. That's not really an option. The GPIO pins are connected to an optional exp= ansion module. When the module is plugged in the pins have dedicated functi= ons. When the module is not present they are by default floating inputs. Th= at's the case our hardware engineer is concerned about. Best regards, =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 --nextPart2564495.D8XtkFrj95 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) iEYEABECAAYFAkjzKlsACgkQ8y9gWxC9vpeM0QCfbgGC7S9+aecaxV07Ubri1T/T CpIAoJB0yFAy/x+sTxQULG8avA2yB8Ep =Clls -----END PGP SIGNATURE----- --nextPart2564495.D8XtkFrj95--