Use memory mapped array for LED matrix

Author: simonbyrne

README.md

@@ -10,13 +10,16 @@ SenseHat.jl requires the Raspbian `sense-hat` package:
 
 ## LED matrix
 
-The `led_display(X)` function will display an 8×8 matrix of colors on the LED matrix (see [ColorTypes.jl](https://github.com/JuliaGraphics/ColorTypes.jl)). `led_clear()` will set all the LEDs to black.
+The main interface is the `led_matrix()` function, which creates an 8×8 array of RGB values (from [ColorTypes.jl](https://github.com/JuliaGraphics/ColorTypes.jl)) which is memory-mapped to the frame buffer of the LED matrix.
 
     using SenseHat
-
-    led_display(SenseHat.JULIA_LOGO)
-    sleep(1)
-    led_clear()
+    using ColorTypes
+    
+    const LED = led_matrix()
+    
+    LED[:] = SenseHat.JULIA_LOGO
+    sleep(3)
+    LED[:] = RGB(0,0,0)
 
 ## Joystick
 

src/SenseHat.jl

@@ -1,7 +1,7 @@
 __precompile__()
 module SenseHat
 
-export led_display, led_clear,
+export led_matrix, RGB565,
     Stick, StickEvent, sticktask, readstick
 
 include("led.jl")

src/led.jl

@@ -1,5 +1,6 @@
 module LED
-export led_display, led_clear, RGB565
+export led_matrix, RGB565
+
 using ColorTypes, FixedPointNumbers
 
 function _led_fb_device()
@@ -44,6 +45,33 @@ ColorTypes.blue(c::RGB565) = U5(c.data & 0x1f, Val{true})
 ColorTypes.ccolor{Csrc<:Colorant}(::Type{RGB565}, ::Type{Csrc}) = RGB565
 ColorTypes.base_color_type(::Type{RGB565}) = RGB565
 
+"""
+    led_matrix()
+
+Returns an 8x8 matrix of `RGB565` elements that is memory-mapped to the Sense HAT LED Matrix.
+
+While it is possible to invoke the function multiple times (each returning different
+arrays), it is generally preferable to assign it once into a `const` variable so as to
+minimise the number of open file handlers.
+
+# Example
+```
+using SenseHat
+using ColorTypes
+
+const LED = led_matrix()
+
+LED[:] = SenseHat.JULIA_LOGO
+sleep(3)
+LED[:] = RGB(0,0,0)
+```
+
+"""
+led_matrix() = Mmap.mmap(LED_FB_DEVICE, Array{RGB565,2}, (8,8); grow=false)
+
+
+
+
 """
     led_display(X)
 
@@ -57,6 +85,7 @@ See also:
 * `led_clear` for clearing the LED matrix.
 """
 function led_display(X)
+    Base.depwarn("`led_display(X)` has been deprecated, use `led_matrix()[:] = X` instead.", :led_display)
     size(X) == (8,8) || throw(DimensionMismatch("Can only display 8x8 images"))
     open(LED_FB_DEVICE, "w") do fb
         for j = 1:8
@@ -73,6 +102,7 @@ end
 Sets the SenseHat LED matrix to all black.
 """
 function led_clear()
+    Base.depwarn("`led_clear()` has been deprecated, use `led_matrix()[:] = SenseHat.RGB565(0,0,0)` instead.", :led_display)
     open(LED_FB_DEVICE, "w") do fb
         for j = 1:8
             for i = 1:8

test/led.jl

@@ -1,6 +1,10 @@
 using SenseHat
 using Base.Test
 
-led_display(SenseHat.JULIA_LOGO)
-sleep(1)
-led_clear()
+using ColorTypes
+
+const LED = led_matrix()
+
+LED[:] = SenseHat.JULIA_LOGO
+sleep(3)
+LED[:] = RGB(0,0,0)

test/runtests.jl

@@ -1,2 +1 @@
-
 include("led.jl")