Merge pull request #107 from pimoroni/patch-temperature-demo

Improved thermometer demo

micropython/examples/pico_display/thermometer.py

@@ -2,24 +2,52 @@
 # 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 
+import utime
+import gc
 
 # Pico Display boilerplate
 import picodisplay as display
 width = display.get_width()
 height = display.get_height()
+gc.collect()
 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) 
+conversion_factor = 3.3 / (65535)
+temp_min = 10
+temp_max = 30
+bar_width = 5
 
 # Set the display backlight to 50%
 display.set_backlight(0.5)
 
 temperatures = []
 
+colors = [(0, 0, 255), (0, 255, 0), (255, 255, 0), (255, 0, 0)]
+
+
+def temperature_to_color(temp):
+    temp = min(temp, temp_max)
+    temp = max(temp, temp_min)
+
+    f_index = float(temp - temp_min) / float(temp_max - temp_min)
+    f_index *= len(colors) - 1
+    index = int(f_index)
+
+    if index == len(colors) - 1:
+        return colors[index]
+
+    blend_b = f_index - index
+    blend_a = 1.0 - blend_b
+
+    a = colors[index]
+    b = colors[index + 1]
+
+    return [int((a[i] * blend_a) + (b[i] * blend_b)) for i in range(3)]
+
+
 while True:
     # fills the screen with black
     display.set_pen(0, 0, 0)
@@ -27,43 +55,36 @@ 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)    
+    temperature = 27 - (reading - 0.706) / 0.001721
     
+    temperatures.append(temperature)
+
     # shifts the temperatures history to the left by one sample
-    if len(temperatures) > 48:  # 240/5
-        temperatures = temperatures[1::]
-    else:
-        temperatures.append(temperature)
+    if len(temperatures) > width // bar_width:
+        temperatures.pop(0)
 
     i = 0
     for t in temperatures:
         # chooses a pen colour based on the temperature
-        display.set_pen(0, 255, 0)
-        if t > 20:
-            display.set_pen(255, 0, 0)
-        elif t < 13:
-            display.set_pen(0, 0, 255)
+        display.set_pen(*temperature_to_color(t))
     
         # draws the reading as a tall, thin rectangle
-        display.rectangle(i, height - (t * 4), 5, height)
+        display.rectangle(i, height - (round(t) * 4), bar_width, height)
 
-        # the next tall thin rectangle needs to be drawn 5 pixels to the right of the last one
-        i += 5
+        # the next tall thin rectangle needs to be drawn
+        # "bar_width" (default: 5) pixels to the right of the last one
+        i += bar_width
     
     # heck lets also set the LED to match
-    display.set_led(0, 255, 0)
-    if temperature > 20:
-        display.set_led(255, 0, 0)
-    elif temperature < 13:
-        display.set_led(0, 0, 255)
+    display.set_led(*temperature_to_color(temperature))
 
     # draws a white background for the text
     display.set_pen(255, 255, 255)
-    display.rectangle(1, 1, 50, 25)
+    display.rectangle(1, 1, 100, 25)
     
     # writes the reading as text in the white rectangle
     display.set_pen(0, 0, 0)
-    display.text("{:.0f}".format(temperature) + "c", 3, 3, 0, 3)  
+    display.text("{:.2f}".format(temperature) + "c", 3, 3, 0, 3)
     
     # time to update the display
     display.update()