Hi Robert, thanks, that improved the situation, but the GPIO is still going low for approx. 500ms. Any further suggestion?
Regards Axel Am Donnerstag, 6. August 2015 16:32:38 UTC+2 schrieb RobertCNelson: > > On Thu, Aug 6, 2015 at 9:28 AM, Axel Barkow <ax...@barkow.name > <javascript:>> wrote: > > Hi, > > > > I need to set a GPIO output high as early as possible during the startup > and > > keep it active until the system shuts down. What I did so far: > > > > - Use GPIO 0.7 for testing > > - Set GPIO0.7 high in python script automatically after startup -> GPIO > > becomes high approx. 24s after power-on > > - Modify device tree to set GPIO0.7 high -> GPIO becomes high approx. 9s > > after startup > > - Set GPIO0.7 high in u-boot scipt (/boot/boot.scr) -> GPIO becomes high > > after approx. 3.5s, but becomes low again after approx. 6s > > > > My problem now is that the GPIO becomes low for approx. 3s after it was > set > > by u-boot and before the device tree. I guess I need to understand the > > kernel boot process a little bit better. Any suggestion, where to start > or > > any hint where to look at? > > use the 'gpio-hog' option so the kernel doesn't re-set the gpio upon > startup... > > See the example to keep the eMMC in reset: > > > https://github.com/beagleboard/linux/blob/4.1/arch/arm/boot/dts/am335x-boneblack-overlay.dts#L28-L36 > > > Regards, > > -- > Robert Nelson > https://rcn-ee.com/ > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
