Added light sensor example to the su

micropython/examples/stellar_unicorn/README.md

@@ -9,6 +9,7 @@
   - [Feature Test With Audio](#feature-test-with-audio)
   - [Fire Effect](#fire-effect)
   - [Lava Lamp](#lava-lamp)
+  - [Light Sensor](#light-sensor)
   - [Nostalgia Prompt](#nostalgia-prompt)
   - [Rainbow](#rainbow)
   - [Scrolling Text](#scrolling-text)
@@ -91,6 +92,14 @@ A pretty, procedural fire effect. Switch between landscape fire and vertical fir
 
 A 70s-tastic, procedural rainbow lava lamp. You can adjust the brightness with LUX + and -.
 
+### Light Sensor
+
+[light_sensor.py](light_sensor.py)
+
+Reads data from the on board light sensor and displays the brightness level of the environment. The display is by default set to auto brightness i.e reacts to the brightness of the environment. 
+- Button A turns auto brightness off 
+- Button B turns auto brightness on
+
 ### Nostalgia Prompt
 
 [nostalgia_prompt.py](nostalgia_prompt.py)

micropython/examples/stellar_unicorn/light_sensor.py

@@ -0,0 +1,128 @@
+import time
+from stellar import StellarUnicorn
+from picographics import PicoGraphics, DISPLAY_STELLAR_UNICORN as DISPLAY
+
+"""
+Auto brightness feature for the stellar unicorn
+Uses the onboard light sensor to detect the light
+The brightness percentage is displayed with brightness auto adjusted
+"""
+# set up unicorn and drawing variables
+su = StellarUnicorn()
+graphics = PicoGraphics(DISPLAY)
+
+WIDTH, HEIGHT = graphics.get_bounds()
+BLACK = graphics.create_pen(0, 0, 0)
+WHITE = graphics.create_pen(255, 255, 255)
+GREY = graphics.create_pen(20, 20, 20)
+HUE_START = 0
+HUE_END = 100
+graphics.set_font("bitmap8")
+
+# Text display sleep time in ms
+TEXT_SLEEP = 500
+
+
+# the onboard light sensor has a wide range from 0 t0 4095
+# It is therefore needed to set a lower max and a higher minimum
+MIN_LS_VALUE = 10
+MAX_LS_VALUE = 295  # 4095 to use the full range
+MIN_RANGE = 0.1
+MAX_RANGE = 1
+
+
+# perform linear interpolation to map a range of values to discrete
+def map_range(
+    x,
+    min_input=MIN_LS_VALUE,
+    max_input=MAX_LS_VALUE,
+    min_output=MIN_RANGE,
+    max_output=MAX_RANGE,
+):
+    return (x - min_input) * (max_output - min_output) / (
+        max_input - min_input
+    ) + min_output
+
+
+# gets the light sensor value from onboard sensor and interpolates it
+# clamps the brightness values
+def calculate_brightness(current_lsv):
+    brightness_val = map_range(current_lsv)
+    if brightness_val > 1:
+        brightness_val = 1
+    elif brightness_val < 0.1:
+        brightness_val = 0.1
+
+    return brightness_val
+
+
+# draws percentage icon
+def draw_percentage(x, y):
+    graphics.rectangle(x + 1, y + 1, 2, 2)
+    graphics.line(x, y + 6, x + 6, y)
+    graphics.rectangle(x + 4, y + 4, 2, 2)
+
+
+# sets up a handy function we can call to clear the screen
+def clear():
+    graphics.set_pen(BLACK)
+    graphics.clear()
+
+
+mode = "auto"
+last = time.ticks_ms()
+while True:
+    current = time.ticks_ms()
+
+    # get light sensor value from the sensor
+    ls_value = su.light()
+    brightness_value = calculate_brightness(ls_value)
+    su.set_brightness(brightness_value)
+    # calculate brightness percentage
+    bp = (brightness_value / MAX_RANGE) * 100
+
+    # deactivate auto brightness by pressing A
+    if su.is_pressed(StellarUnicorn.SWITCH_A):
+        print("Auto brightness off")
+        mode = "off"
+
+    # reactivate auto brightness by pressing A
+    if su.is_pressed(StellarUnicorn.SWITCH_B):
+        print("Auto brightness on")
+        mode = "auto"
+
+    # set brightness to default value if off
+    if mode == "off":
+        su.set_brightness(0.5)
+
+    # set text update rate after a certain time to reduce flickering
+    if current - last >= TEXT_SLEEP:
+        clear()
+
+        # calculate colour from the brightness value
+        hue = max(0, HUE_START + ((bp - 0) * (HUE_END - HUE_START) / (100 - 0)))
+
+        # create pens with this colour (and with the high / low colours)
+        CURRENT_COLOUR = graphics.create_pen_hsv(hue / 360, 1.0, 0.8)
+        HIGH_COLOUR = graphics.create_pen_hsv(HUE_END / 360, 1.0, 0.8)
+        LOW_COLOUR = graphics.create_pen_hsv(HUE_START / 360, 1.0, 0.8)
+
+        # draw the text
+        graphics.set_pen(CURRENT_COLOUR)
+        graphics.text(f"{bp:.0f}", 0, 1, scale=1)
+        # measure the rest of the text before drawing to right align it
+        text_width = graphics.measure_text(f"{bp:.0f}/°", scale=1)
+
+        draw_percentage(10, 1)
+
+        # draw a bar for the background
+        graphics.set_pen(GREY)
+        graphics.rectangle(0, 9, WIDTH, 10)
+
+        # draw a bar for the current brightness percentage
+        graphics.set_pen(CURRENT_COLOUR)
+        graphics.rectangle(0, 9, int((bp / 100) * WIDTH), 10)
+        last = current
+
+    # update the display
+    su.update(graphics)