add Explorer examples

micropython/examples/pico_explorer/rainbow.py

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+## This example borrows a CircuitPython hsv_to_rgb function to cycle through some rainbows on Pico Explorer's screen and RGB LED . If you're into rainbows, HSV (Hue, Saturation, Value) is very useful!
+
+import utime
+import picoexplorer as display
+
+# Set up and initialise Pico Explorer
+buf = bytearray(display.get_width() * display.get_height() * 2)
+display.init(buf)
+
+# From CPython Lib/colorsys.py
+def hsv_to_rgb(h, s, v):
+    if s == 0.0:
+        return v, v, v
+    i = int(h*6.0)
+    f = (h*6.0) - i
+    p = v*(1.0 - s)
+    q = v*(1.0 - s*f)
+    t = v*(1.0 - s*(1.0-f))
+    i = i%6
+    if i == 0:
+        return v, t, p
+    if i == 1:
+        return q, v, p
+    if i == 2:
+        return p, v, t
+    if i == 3:
+        return p, q, v
+    if i == 4:
+        return t, p, v
+    if i == 5:
+        return v, p, q
+
+h = 0
+
+while True:
+    h += 1
+    r, g, b = [int(255 * c) for c in hsv_to_rgb(h / 360.0, 1.0, 1.0)]  # rainbow magic
+    display.set_pen(r, g, b)  # Set pen to a converted HSV value
+    display.clear()           # Fill the screen with the colour
+    display.set_pen(0, 0, 0)  # Set pen to black
+    display.text("pico disco!", 25, 20, 240, 6)  # Add some text
+    display.text("\o/ \o/ \o/ \o/ \o/ \o/ \o/ \o/ \o/", 25, 120, 240, 4)  # and some more text
+    display.text("oontz oontz oontz", 25, 220, 240, 2)  # and a bit more tiny text
+    display.update()          # Update the display
+    utime.sleep(1.0 / 60)

micropython/examples/pico_explorer/thermometer.py

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+# This example takes the temperature from the Pico's onboard temperature sensor, and displays it on Pico Explorer, along with a little pixelly graph.
+# It's based on the thermometer example in the "Getting Started with MicroPython on the Raspberry Pi Pico" book, which is a great read if you're a beginner!
+
+import machine 
+import utime 
+
+# Pico Explorer boilerplate
+import picoexplorer as display
+width = display.get_width()
+height = display.get_height()
+display_buffer = bytearray(width * height * 2)
+display.init(display_buffer)
+
+# reads from Pico's temp sensor and converts it into a more manageable number
+sensor_temp = machine.ADC(4) 
+conversion_factor = 3.3 / (65535) 
+
+i = 0
+
+while True:
+    # the following two lines do some maths to convert the number from the temp sensor into celsius
+    reading = sensor_temp.read_u16() * conversion_factor
+    temperature = round(27 - (reading - 0.706) / 0.001721)    
+    
+    # this if statement clears the display once the graph reaches the right hand side of the display
+    if i >= (width + 1):
+        i = 0
+        display.set_pen(0, 0, 0)
+        display.clear()
+
+    # chooses a pen colour based on the temperature
+    display.set_pen(0, 255, 0)
+    if temperature > 20:
+        display.set_pen(255, 0, 0)
+    if temperature < 13:
+        display.set_pen(0, 0, 255)
+           
+    # draws the reading as a tall, thin rectangle
+    display.rectangle(i, height - (temperature * 6), 6, height)
+    
+    # draws a white background for the text
+    display.set_pen(255, 255, 255)
+    display.rectangle(1, 1, 65, 33)
+    
+    # writes the reading as text in the white rectangle
+    display.set_pen(0, 0, 0)
+    display.text("{:.0f}".format(temperature) + "c", 3, 3, 0, 4)  
+    
+    # time to update the display
+    display.update()
+    
+    # waits for 5 seconds
+    utime.sleep(5) 
+    
+    # the next tall thin rectangle needs to be drawn 6 pixels to the right of the last one
+    i += 6