Rewrote devices on Beaglebone. Passes precompile, but needs proper testing.

src/BeagleBone/GPIO.jl

 """
 Lowest form of communication with the GPIO pins. The available pins are
-listed in the "channel" parameter, and appear as directories in /sys/class/gpio.
-
-Any of these GPIOs can be run in various ways, with any operation specified by an
-Int32 value.
+listed in the "channel" parameter, and appear as directories in /sys/class/gpio
+after being exported.
 
 For instance, to setup a GPIO on "gpio112", configure it as an output pin and set
 it to high, the following code would be used.
 
-gpio = GPIO(1)
-write!(gpio, (2,"out"))
-write!(gpio, (1, "1"))
+  gpio = GPIO(1)
+  write!(gpio, (2,"out"))
+  write!(gpio, (1, "1"))
 
 The operation of reading the current output value of the GPIO is done by
 
-read(gpio, 1)
+  read(gpio, 1)
 
+See the test/BeagleBone/GPIO_test.jl for more examples.
 """
+
 type GPIO <: IO_Object
   i::Int32
   basedir::String
   filestreams::Array{IOStream,1}
   function GPIO(i::Int32)
-    (i <= 0 || i > length(channels)) && error("Invalid GPIO index: $i")
+    (i <= 0 || i > length(gpio_channels)) && error("Invalid GPIO index: $i")
 
     # If the tests re being run, a dummy filesystem is created
-    if isdefined(:RUNNING_TESTS)
-      # Export a dummy file system for testing
-      basedir = "$(pwd())/testfilesystem/gpio"
-      try
-        println("$(basedir)/$(channels[i])")
-        mkpath("$(basedir)/$(channels[i])")
-      catch
-        error("Could not export the GPIO device for channel $(channels[i]) for testing as the directory $(basedir)/$(channels[i]) already exists.")
-      end
-      try
-        f = open("$(basedir)/$(channels[i])/value", "w"); write(f,"0"); close(f);
-        f = open("$(basedir)/$(channels[i])/direction", "w"); write(f,"0"); close(f);
-        f = open("$(basedir)/$(channels[i])/edge", "w"); write(f,"0"); close(f);
-      catch
-        error("Could not open the requested GPIO testfiles for channel $(channels[i]).")
-      end
-    else
-      basedir = "/sys/class/gpio"
-      # TODO Export for real-time use
-    end
+    basedir = export_gpio(i)
 
     # setup IOstreams
-    value_filestream = open("$(basedir)/$(channels[i])/value","r+")
-    direction_filestream = open("$(basedir)/$(channels[i])/direction","r+")
-    edge_filestream = open("$(basedir)/$(channels[i])/edge","r")
+    value_filestream = open("$(basedir)/$(gpio_channels[i])/value","r+")
+    direction_filestream = open("$(basedir)/$(gpio_channels[i])/direction","r+")
+    edge_filestream = open("$(basedir)/$(gpio_channels[i])/edge","r")
 
     # Initialize object
     return new(i, basedir, [value_filestream, direction_filestream, edge_filestream])
   end
 end
 
-writeOperations = [["1", "0"],["in", "out"],["none","rising","falling","both"]]
-
-channels =[
-"gpio112"
-"gpio114"
-"gpio115"
-"gpio116"
-"gpio14"
-"gpio15"
-"gpio2"
-"gpio20"
-"gpio22"
-"gpio23"
-"gpio26"
-"gpio27"
-"gpio3"
-"gpio30"
-"gpio31"
-"gpio4"
-"gpio44"
-"gpio45"
-"gpio46"
-"gpio47"
-"gpio48"
-"gpio49"
-"gpio5"
-"gpio50"
-"gpio51"
-"gpio60"
-"gpio61"
-"gpio65"
-"gpio66"
-"gpio67"
-"gpio68"
-"gpio69"
-"gpio7"
-]
-
 """
   write!(gpio::GPIO, args::Tuple{Int32,String}, debug::Bool=false)
 Writes an entry to an operation on a GPIO, of the form args = (operation, entry).
@@ -101,10 +44,12 @@ Writes an entry to an operation on a GPIO, of the form args = (operation, entry)
 function write!(gpio::GPIO, args::Tuple{Int32,String}, debug::Bool=false)
   debug && return
   operation, entry = args[1], args[2]
-  (operation < 1 || operation > length(gpio.filestreams)) && error("Invalid GPIO operation: $operation")
-  if entry in writeOperations[operation]
-    write(gpio.filestreams[operation], entry)
+  # Only filestreams 1 and 2 are writable
+  operation ∉ [1,2] && error("Invalid GPIO operation $operation for writing")
+  if entry in gpio_operations[operation]
     seekstart(gpio.filestreams[operation])
+    write(gpio.filestreams[operation], "$entry\n")
+    flush(gpio.filestreams[operation])
   else
     error("Invalid entry for GPIO operation $(operation): $(entry)")
   end
@@ -116,9 +61,10 @@ Reads the current value from an operation on a GPIO.
 """
 function read(gpio::GPIO, operation::Int32, debug::Bool=false)
   debug && return
-  (operation < 1 || operation > length(gpio.filestreams)) && error("Invalid GPIO operation: $operation")
-  l = readline(gpio.filestreams[operation])
+  # Filestreams 1, 2 and 3 are readable
+  operation ∉ [1,2,3] && error("Invalid GPIO operation: $operation for reading")
   seekstart(gpio.filestreams[operation])
+  l = readline(gpio.filestreams[operation])
   return l
 end
 
@@ -139,16 +85,44 @@ function teardown(gpio::GPIO, debug::Bool=false)
     # Remove the dummy file system for testing
     basedir = "$(pwd())/testfilesystem/gpio"
     try
-      rm("$(gpio.basedir)/$(channels[gpio.i])"; recursive=true)
+      rm("$(gpio.basedir)/$(gpio_channels[gpio.i])"; recursive=true)
     catch
-      error("Could not remove the requested GPIO testfiles for channel $(channels[i]).")
+      error("Could not remove the requested GPIO testfiles for channel $(gpio_channels[i]).")
     end
   else
     # Remove the file system
     filename = "/sys/class/gpio/unexport"
-    #TODO Verify if this is the correct command to send to unexport...
-    write(filename, channels[gpio.i])
+    #TODO Verify if this is the correct command to send to unexport
+    write(filename, gpio_channels[gpio.i])
+  end
+end
+
+"""
+  export_gpio(i::Int32, debug::Bool=false)
+Export the GPIO file system, either for real-time or testing usecases.
+"""
+function export_gpio(i::Int32)
+  if isdefined(:RUNNING_TESTS)
+    # Export a dummy file system for testing
+    basedir = "$(pwd())/testfilesystem/gpio"
+    try
+      #println("$(basedir)/$(gpio_channels[i])")
+      mkpath("$(basedir)/$(gpio_channels[i])")
+    catch
+      error("Could not export the GPIO device for channel $(gpio_channels[i]) for testing as the directory $(basedir)/$(gpio_channels[i]) already exists.")
+    end
+    try
+      f = open("$(basedir)/$(gpio_channels[i])/value", "w"); write(f,"0"); close(f);
+      f = open("$(basedir)/$(gpio_channels[i])/direction", "w"); write(f,"0"); close(f);
+      f = open("$(basedir)/$(gpio_channels[i])/edge", "w"); write(f,"0"); close(f);
+    catch
+      error("Could not open the requested GPIO testfiles for channel $(gpio_channels[i]).")
+    end
+  else
+    basedir = "/sys/class/gpio"
+    # TODO Export for real-time use
   end
+  return basedir
 end
 
 """