From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ned Forrester Subject: Re: SPI troubles Date: Mon, 15 Mar 2010 10:38:38 -0400 Message-ID: <4B9E466E.3040405@whoi.edu> References: <4b9d9f11.9a15f10a.3902.6dc3@mx.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, beagleboard-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ben Gamari Return-path: In-Reply-To: <4b9d9f11.9a15f10a.3902.6dc3-ATjtLOhZ0NVl57MIdRCFDg@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On 03/14/2010 10:44 PM, Ben Gamari wrote: > > When measuring the SIMO signal on the expansion connector with my daughterboard > connected, I noticed that the daughterboard's level shifter appeared to be > driving the signal higher than it should, to ~2.9 Volts. I then checked the > 1.8V rail voltage and found that it too was higher than expected, again at 2.9 > volts. When I unplug the daughterboard, the 1.8V rail voltage returns to its > expected value. > > I'm both perplexed and concerned with this behavior. I completely fail to > see how my board is raising the voltage on the 1.8V rail (schematic available > at [3]). While the BeagleBoard seems quite stable, I'm very concerned that > perhaps the daughterboard over-drove the SIMO ball and burned out some subset > of the OMAP. Regardless, as mentioned earlier, I have verified the > functionality of the same ball as a GPIO input. Thus, I am thoroughly confused. > Is it possible that the ball's GPIO receiver could remain functional while the > McSPI receiver is burned out? > > [3] http://goldnerlab.physics.umass.edu/git?p=tracker-board.git;a=summary I'd be happy to check your circuit for you, if it were posted in a more widely used format. How about a PDF of the schematic. -- Ned Forrester nforrester-/d+BM93fTQY@public.gmane.org Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/ http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev