Add functional GPIO code for writing high/low to any pin

src/BeagleBone/BeagleBone.jl

@@ -3,9 +3,10 @@
 # read(::T, identifier)
 
 include("SysLED.jl")
+include("GPIO.jl")
 
 #List of available devices and their constructors
-const DEVICES = Dict("sysled" => SysLED())
+const DEVICES = Dict("sysled" => SysLED(), "gpio" => GPIO())
 
 """
     dev = getdev(devname)

src/BeagleBone/GPIO.jl

+"""
+Lowest form of communication woth the GPIO pins. The available pins are
+listed in the "channel" parameter, and appear as directories in /sys/class.
+Any of these GPIOs can be run in various ways, with any operation specified
+by a sequence of three entries
+
+  (channel, operation, entry) = (int32, int32, String)
+
+For instance, if the GPIO "gpio30" is to be configured as a output pin and set
+to high, the following two writes aould be done.
+
+  write!(GPIO, 14, 2, "out")
+  write!(GPIO, 14, 1, "1")
+
+"""
+struct GPIO
+end
+
+writeOperations = [
+    Dict("dir" => "value",     "entries"=>["1", "0"])
+    Dict("dir" => "direction", "entries"=>["in", "out"])
+]
+
+readOperations = [
+    "value"
+    "direction"
+    "edge"
+]
+
+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"
+]
+
+function write!(::GPIO, index::Int32, operation::Int32, entry::Bool)
+    (index <= 0 || index > length(channels)) && error("Invalid GPIO index: $index")
+    (operation <= 0 || operation > length(writeOperations)) && error("Invalid GPIO operation: $operation")
+    filename = "/sys/class/gpio/$(channels[index])/$(writeOperations[operation]["dir"])"
+
+    value = writeOperations[operation]["entries"][entry ? 1 : 2]
+    file = open(filename, "r+")
+
+    write(file, "$(value)")
+    close(file)
+    return
+end
+
+#function Base.read(::SysLED, ind::Int32)
+#    (ind < 0 || ind > length(channels)) && error("Invalid SysLEND ind: $ind")
+#    println("not yet supported")
+#    l = 0
+#    return l == "1"
+#end