Missing support for USR% leds on BBB

Hi, I’m testing Blinka on a BBB, and I have this problem when trying to use User Leds

debian@beaglebone:/var/lib/cloud9/python$ sudo python3 blinka_blink.py
hello blinky!
Traceback (most recent call last):
  File "blinka_blink.py", line 9, in <module>
    led = digitalio.DigitalInOut(board.LED_USR1)
  File "/usr/local/lib/python3.5/dist-packages/Adafruit_Blinka-1.2.7.dev3+g5d33134-py3.5.egg/digitalio.py", line 67, in __init__
    self.direction = Direction.INPUT
  File "/usr/local/lib/python3.5/dist-packages/Adafruit_Blinka-1.2.7.dev3+g5d33134-py3.5.egg/digitalio.py", line 93, in direction
    self._pin.init(mode=Pin.IN)
  File "/usr/local/lib/python3.5/dist-packages/Adafruit_Blinka-1.2.7.dev3+g5d33134-py3.5.egg/adafruit_blinka/microcontroller/am335x/pin.py", line 30, in init
    GPIO.setup(self.id, GPIO.IN)
ValueError: Set gpio mode failed, missing file or invalid permissions.

Thank you for your attention

[pdp7]

I can reproduce the behavior directly in Adafruit_BBIO by calling GPIO.setup("USR1", GPIO.IN) instead of GPIO.setup("USR1", GPIO.OUT)

import Adafruit_BBIO.GPIO as GPIO
GPIO.setup("USR1", GPIO.IN)

results in error:

Traceback (most recent call last):
  File "/home/debian/test-usr.py", line 2, in <module>
    GPIO.setup("USR1", GPIO.IN)
ValueError: Set gpio mode failed, missing file or invalid permissions.

and strace shows the bad path:

open("/sys/devices/platform/ocp/ocp:USR01_pinmux/state", O_WRONLY|O_CREAT|O_TRUNC, 0666) = -1 ENOENT (No such file or directory)

[pdp7]

I believe this behavior is due to a bug in Adafruit_BBIO where USRn LED is setup initially in INPUT mode instead of OUTPUT mode.

I hard coded the pin to be an output to test:

diff --git a/src/adafruit_blinka/microcontroller/am335x/pin.py b/src/adafruit_blinka/microcontroller/am335x/pin.py
index 71715e6..0455454 100644
--- a/src/adafruit_blinka/microcontroller/am335x/pin.py
+++ b/src/adafruit_blinka/microcontroller/am335x/pin.py
@@ -24,12 +24,17 @@ class Pin:
         return self.id == other
 
     def init(self, mode=IN, pull=None):
+        print("am335x: init(): self.id {0}".format(self.id))
+        # HARD CODE TO OUTPUT
+        mode = self.OUT
         if mode != None:
             if mode == self.IN:
+                print("am335x: self.IN: self.id {0}".format(self.id))
                 self._mode = self.IN
                 GPIO.setup(self.id, GPIO.IN)
             elif mode == self.OUT:
                 self._mode = self.OUT
+                print("am335x: self.OUT: self.id {0}".format(self.id))
                 GPIO.setup(self.id, GPIO.OUT)
             else:
                 raise RuntimeError("Invalid mode for pin: %s" % self.id)

This now works:

led = digitalio.DigitalInOut(board.LED_USR0)

strace shows that the correct path is being used:

access("/sys/class/leds/beaglebone:green:usr0/brightness", W_OK) = 0
open("/sys/class/leds/beaglebone:green:usr0/brightness", O_WRONLY) = 4

I’ll investigate further the root cause in Adafruit_BBIO