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fix(examples): Migrate buzzer tone() to hardware PWM Timer. #273

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Merged
nedseb merged 2 commits into from
Mar 28, 2026
Merged

fix(examples): Migrate buzzer tone() to hardware PWM Timer. #273

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1836efa
refactor(mcp23009e): Migrate tone() to Timer dpad_piano example
Charly-sketch Mar 27, 2026
ef28b74
fix(mcp23009e): Fix Copilot review comments in dpad_piano example.
nedseb Mar 28, 2026
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73 changes: 41 additions & 32 deletions lib/mcp23009e/examples/dpad_piano.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,16 +10,21 @@
MENU exits the piano mode.
"""

from time import sleep_ms, sleep_us, ticks_diff, ticks_ms
from time import sleep_ms

from machine import I2C, Pin
from mcp23009e import MCP23009E
from mcp23009e.const import *
from pyb import Timer

# Board pins
SPEAKER = Pin("SPEAKER", Pin.OUT)
MENU_BUTTON = Pin("MENU_BUTTON", Pin.IN, Pin.PULL_UP)

# Hardware PWM on SPEAKER pin (PA11 = TIM1_CH4)
buzzer_tim = Timer(1, freq=1000)
buzzer_ch = buzzer_tim.channel(4, Timer.PWM, pin=Pin("SPEAKER"))
buzzer_ch.pulse_width_percent(0)

# I2C and expander setup
i2c = I2C(1)
reset_expander = Pin("RST_EXPANDER", Pin.OUT)
Expand Down Expand Up @@ -50,21 +55,18 @@
}


def tone(pin, freq, duration_ms):
"""Generate a square wave on the buzzer pin."""
if freq == 0:
sleep_ms(duration_ms)
def tone(freq):
"""Start a tone using hardware PWM."""
if freq <= 0:
no_tone()
return
buzzer_tim.freq(freq)
buzzer_ch.pulse_width_percent(50)

period_us = int(1_000_000 / freq)
half_period_us = period_us // 2
end_time = ticks_ms() + duration_ms

while ticks_diff(end_time, ticks_ms()) > 0:
pin.on()
sleep_us(half_period_us)
pin.off()
sleep_us(half_period_us)
def no_tone():
"""Silence the buzzer."""
buzzer_ch.pulse_width_percent(0)


def setup_buttons():
Expand Down Expand Up @@ -121,40 +123,47 @@ def dpad_piano():

last_note = None
last_octave = None
last_freq = 0

try:
while True:
# MENU button is a direct MCU pin, not an MCP23009E pin
if MENU_BUTTON.value() == 0:
print("Menu button pressed, exiting piano.")
wait_menu_release()
break

pressed = get_pressed_buttons()
frequency, note_name, octave = select_frequency(pressed)

if pressed:
frequency, note_name, octave = select_frequency(pressed)

if note_name != last_note or octave != last_octave:
print(
"Playing:",
note_name,
"-",
frequency,
"Hz",
"(" + octave + " octave)",
)
last_note = note_name
last_octave = octave

tone(SPEAKER, frequency, 60)
else:
if frequency == 0:
if last_freq != 0:
no_tone()
last_note = None
last_octave = None
last_freq = 0
sleep_ms(20)
Comment on lines 124 to 144
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Copilot AI Mar 27, 2026

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last_freq is initialized to None but later compared to 0, which causes an extra no_tone() call on the first loop iteration even before any note is played. Consider initializing last_freq to 0 (or removing last_freq entirely and calling no_tone() unconditionally when frequency == 0, since it is idempotent).

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continue

if note_name != last_note or octave != last_octave:
print(
"Playing:",
note_name,
"-",
frequency,
"Hz",
"(" + octave + " octave)",
)
tone(frequency)
last_note = note_name
last_octave = octave
last_freq = frequency

sleep_ms(20)

except KeyboardInterrupt:
print("\nPiano stopped.")
finally:
no_tone()


dpad_piano()
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