Hi Gerald, thanks, I need to check, if this is a possible solution. I want to use the output to keep the BBB powered, when the external start signal goes low and power the whole system down depending on some software decisions. Therefore the output is connected to a shutdown pin of a voltage regulator, whcih provides the 5V. I'm afraid adding a pullup here will keep the system active forever...
Regards Axel Am Donnerstag, 6. August 2015 16:32:44 UTC+2 schrieb Gerald: > > Add a pullup or just use a GPIO that defaults to high. Nothing is faster > than that. > > Gerald > > 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? >> >> Regards >> >> Axel >> >> -- >> 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...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Gerald > > ger...@beagleboard.org <javascript:> > http://beagleboard.org/ > -- 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.
