On 11/28/2015 1:34 PM, Riley Porter wrote: > So I woke up this morning and gave this a go. I think there still might be > something wrong here. So I have all of my pins that I wish to use set to > 0x27 input with pulldown enabled. Which I assume means they will be pulled > low to ground. (stating the obvious here) > > I went to /sys/class/gpio/ and looked to see if they were "exported" but > there were not? I am I wrong on understanding that applying a device tree > does not export the GPIO pins to /sys/class/gpio?
A device tree overlay _can_ export GPIO pins (using the gpio-of-helper driver), but it doesn't have to. Note that there is a difference between *exporting* the GPIO pin and setting it's pinmux to a specific value. The device tree file you sent previously sets up pinmux values, but doesn't actually export any GPIOs. > I went ahead and exported 48 (P9_15 which is set to 0x27) to export. I > then: > > *root /sys/class/gpio/gpio48 # cat value**1* > > *root /sys/class/gpio/gpio48 # cat directionin* > > I tried this for gpio30 (P9_11) and it works as expected. When I press the > button that ties it to 3v3 it registers a 1 all other times its a 0. > > I do not know why I am reading a HIGH on this pin? There is nothing hooked > up to this pin externally (as far as i know internally as well). Perhaps I > should just select another pin and move on. But I after going this far I > would rather beat a dead horse and get you guy's input on this? Any > thoughts? Per the schematic, it looks like P9_15 is hooked to GPIO1_16 (ball R13) as well as GPIO2_0 (ball T13) via resistors R160 and R161, both of which are populated on my board. What is the pinmux setting for GPIO2_0? It could be fighting your pull-down setting if it's set to pull up or drive a high level. -- Charles Steinkuehler [email protected] -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
