Add piano (tone playback) demo.

Author: tdicola

examples/piano.py

@@ -0,0 +1,77 @@
+# MPR121 piano demo.
+# Listens to the first 7 inputs of the MPR121 and plays a middle scale note
+# when an input is touched.  Note only one note is played at a time!
+# Author: Tony DiCola
+import time
+
+import board
+import nativeio
+
+# Uncomment _one_ of the following lines depending on how your board supports I2C.
+# For hardare I2C (SAMD21/M0 boards):
+import nativeio as io
+# For software I2C (ESP8266):
+#import bitbangio as io
+
+# Import MPR121 module.
+import adafruit_mpr121
+
+
+# Configure PWM buzzer and other state:
+BUZZER_PIN = board.D9
+TONE_ON_DUTY  = 2**15  # Duty cycle of tone when turned on, a square wave.
+TONE_OFF_DUTY = 0      # Duty cycle of tone when turned off, 0 or no signal.
+NOTE_FREQS = [ 261,  # Input 0 = 261 hz = middle C
+               294,  # Input 1 = middle D
+               329,  # Input 2 = middle E
+               349,  # Input 3 = middle F
+               392,  # Input 4 = middle G
+               440,  # Input 5 = middle A
+               493,  # Input 6 = middle B
+               0,    # Input 7 = nothing (set to a frequency in hertz!)
+               0,    # Input 8
+               0,    # Input 9
+               0,    # Input 10
+               0 ]   # Input 11
+
+
+# Create I2C bus.
+i2c = io.I2C(board.SCL, board.SDA)
+
+# Create MPR121 class.
+mpr121 = adafruit_mpr121.MPR121(i2c)
+# Note you can optionally change the address of the device:
+#mpr121 = adafruit_mpr121.MPR121(i2c, address=0x91)
+
+# Setup buzzer PWM output.
+buzzer = nativeio.PWMOut(BUZZER_PIN, duty_cycle=TONE_OFF_DUTY, frequency=440,
+                         variable_frequency=True)
+
+# Main loop.
+# First grab an initial touch state for all of the inputs.  The touched()
+# function can quickly get the state of all input pins and returns them as a
+# 12-bit value with a bit set to 1 for each appropriate input (i.e. bit 0 is
+# input 0, bit 1 is input 1, etc.)
+last = mpr121.touched()
+while True:
+    # Every loop iteration get an updated touch state and look to see if it
+    # changed since the last iteration.
+    current = mpr121.touched()
+    if last != current:
+        # Some pin changed, turn off playback and look for any touched pins.
+        buzzer.duty_cycle = TONE_OFF_DUTY
+        # Loop through all 12 inputs (0-11) and look at their bits in the
+        # current touch state.  A bit that's set is touched!
+        for i in range(12):
+            if (1 << i) & current > 0:
+                print('Input {} touched!'.format(i))
+                # Grab the frequency for the associated pin and check that it's
+                # not zero (unused).
+                freq = NOTE_FREQS[i]
+                if freq != 0:
+                    # Pin with a specified frequency was touched, play the tone!
+                    buzzer.frequency = NOTE_FREQS[i]
+                    buzzer.duty_cycle = TONE_ON_DUTY
+    # Update touch state and delay a bit before next loop iteration.
+    last = current
+    time.sleep(0.01)