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I am trying to create a device tree overlay for a BeagleBone Black per these instructions: http://derekmolloy.ie/gpios-on-the-beaglebone-black-using-device-tree-overlays/. I followed the directions exactly as shown and was not told of any errors, except after I try to apply the overlay (with echo DM-GPIO-Test > $SLOTS), it doesn't seem to actually work. Using cat $SLOTS shows everything how it is supposed to be:

root@beaglebone:/lib/firmware# cat $SLOTS
 0: 54:PF--- 
 1: 55:PF--- 
 2: 56:PF--- 
 3: 57:PF--- 
 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
 5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
 6: ff:P-O-L Override Board Name,00A0,Override Manuf,DM-GPIO-Test

However, if I cat $PINS none of the values have changed from the original, and the dmesg command does not return any of the expected output (shown on the linked site). I have also looked at several other sites about overlays, with more or less the same instructions, which are also unsuccessful. I've tried other overlays as well, and tested on multiple BeagleBone Black boards, with no success.

I am using the 3.8.13 kernel with Angstrom, essentially unmodified except for what's in that tutorial.

siamesedrummer
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  • First of all, just a tip: when setting the SLOTS environment variable, use a "*" in place of the number. `export SLOTS=/sys/devices/bone_capemgr.*/slots` Just a nice fail-safe I guess. Now for the real problem, have you tried checking the pingroups to see if the overlay actually worked? `cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pingroups` – woojoo666 Jan 28 '14 at 13:04
  • Also, I highly recommend this tutorial: http://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/overview – woojoo666 Jan 28 '14 at 13:06
  • Yup, I know about the $SLOTS thing. I have tried that tutorial as well. I'm having this problem with other DTOs as well, even the default ones found in /lib/firmware/ that came with the BeagleBone. – siamesedrummer Jan 29 '14 at 00:21
  • did you try checking the pingroups? were any new pins enabled? – woojoo666 Jan 29 '14 at 02:24
  • like "cat $PINS"? No, all were the same as previously. – siamesedrummer Jan 29 '14 at 22:53
  • do you have DM-GPIO-Test.dts (the source file)? If you could pastebin it to me, maybe there's something wrong with the file itself. Also, any trouble with the adafruit tutorial? – woojoo666 Jan 30 '14 at 05:28
  • The source file is here: https://github.com/derekmolloy/boneDeviceTree/blob/master/overlay/DM-GPIO-Test.dts – siamesedrummer Jan 31 '14 at 21:18
  • Any problems with the adafruit tutorial? – woojoo666 Feb 01 '14 at 06:03
  • Same thing as with the other tutorial. No "errors" when applying the DTO, but dmesg shows nothing being applied and the pin modes don't actually change. – siamesedrummer Feb 01 '14 at 20:25
  • Did you make sure the overlay isn't already loaded when you apply it manually? It might be already loading on bootup. and can you edit the question to add the output from `dmesg | tail` after loading the overlay? – woojoo666 Feb 02 '14 at 05:35
  • The overlay is not already loaded. I didn't include dmesg because nothing pertinent showed up i.e. the overlay was not applied. I don't have my beaglebone on my at the moment but I can do it later if you'd like. – siamesedrummer Feb 02 '14 at 21:53

1 Answers1

-1

you have to run the command as root.

InvAdErZz
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