From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1Rvkzt-00019i-0u for barebox@lists.infradead.org; Fri, 10 Feb 2012 07:34:22 +0000 Date: Fri, 10 Feb 2012 08:34:06 +0100 From: Sascha Hauer Message-ID: <20120210073406.GD3852@pengutronix.de> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: barebox-bounces@lists.infradead.org Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: how to read GPIO values from command line? To: "Robert P. J. Day" Cc: "U-Boot Version 2 (barebox)" On Thu, Feb 09, 2012 at 11:34:55AM -0500, Robert P. J. Day wrote: > > i'm looking at the docs and tried the obvious but it didn't seem to > work. in order to recognize the version of beagleboard, i can see > what happens in the u-boot code: > > /* > * Routine: get_board_revision > * Description: Detect if we are running on a Beagle revision Ax/Bx, > * C1/2/3, C4 or xM. This can be done by reading > * the level of GPIO173, GPIO172 and GPIO171. This should > * result in > * GPIO173, GPIO172, GPIO171: 1 1 1 => Ax/Bx > * GPIO173, GPIO172, GPIO171: 1 1 0 => C1/2/3 > * GPIO173, GPIO172, GPIO171: 1 0 1 => C4 > * GPIO173, GPIO172, GPIO171: 0 0 0 => xM > */ > int get_board_revision(void) > { > int revision; > > if (!gpio_request(171, "") && > !gpio_request(172, "") && > !gpio_request(173, "")) { > > gpio_direction_input(171); > gpio_direction_input(172); > gpio_direction_input(173); > > revision = gpio_get_value(173) << 2 | > gpio_get_value(172) << 1 | > gpio_get_value(171); > } else { > printf("Error: unable to acquire board revision GPIOs\n"); > revision = -1; > } > > return revision; > } > > however, in the latest kernel tree, it seems things have changed > slightly: > > /* > * OMAP3 Beagle revision > * Run time detection of Beagle revision is done by reading GPIO. > * GPIO ID - > * AXBX = GPIO173, GPIO172, GPIO171: 1 1 1 > * C1_3 = GPIO173, GPIO172, GPIO171: 1 1 0 > * C4 = GPIO173, GPIO172, GPIO171: 1 0 1 > * XMA/XMB = GPIO173, GPIO172, GPIO171: 0 0 0 > * XMC = GPIO173, GPIO172, GPIO171: 0 1 0 > */ > > now that's useful since there are now allegedly different values for > xM A/B, and xM C, and i have a rev C. > > so what exactly does one do to read those values? i tried: > > barebox@Texas Instrument's Beagle:/ gpio_direction_input 171 > barebox@Texas Instrument's Beagle:/ gpio_get_value 171 > > but what do i check? the shell variable $? i'm not sure what i > should do next. Yes, check $?. This assumes that your iomux is set up correctly as Eric already mentioned. I wonder that there is no iomux setup for the panda board. You can copy it from U-Boot. It has to arrays of iomux setup: core_padconf_array_essential and core_padconf_array_non_essential Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox