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Ring Tone Text Transfer Language Parser

This library can parse RTTTL text lines and delivers the frequency and duration for each note.

A typical RTTTL string looks like this:


You can find many more sample ring tones here:

You can find a description of RTTTL here:

Using RTTTL on the pyboard

Instantiate an instance of the RTTTL class, passing in the tune string to the constructor.

tune = RTTTL('Entertainer:d=4,o=5,b=140:8d,8d#,8e,c6,8e,c6,8e,2c.6,8c6,8d6,8d#6,8e6,8c6,8d6,e6,8b,d6,2c6,p,8d,8d#,8e,c6,8e,c6,8e,2c.6,8p,8a,8g,8f#,8a,8c6,e6,8d6,8c6,8a,2d6')

Then use the notes generator to enumerate the notes in the tune. The notes generator will return a tuple, where the first entry in the tuple contains the frequency of the note (in Hz) and the second entry in the tuple contains the duration of the note.

for freq, msec in tune.notes():
    play_tone(freq, msec)

When using a piezo you basically provide a 50% PWM signal to the piezo using the frequency of the note. Some piezo speakers can vary the volume by using a different duty cycle. The piezo on the G30DEV board Dave Hylands this on, it didn't seem to make any difference.

In order to distinguish consecutive notes, you need a small gap between the notes. Dave Hylands chose to use 90% of the duration to play the tone, and 10% of duration to play silence.

Dave Hylands used the following play_tone routine on the G30DEV board:

import pyb
buz_tim = pyb.Timer(3, freq=440)
buz_ch =, pyb.Timer.PWM, pin=pyb.Pin.board.BUZZER, pulse_width=0)
def play_tone(freq, msec):
    print('freq = {:6.1f} msec = {:6.1f}'.format(freq, msec))
    if freq > 0:
    pyb.delay(int(msec * 0.9))
    pyb.delay(int(msec * 0.1))

Dave Hylands put a recording of the above on YouTube:

The G30DEV board definition files for MicroPython can be found here:

When using pin Y2 on a pyboard v1.0, change the timer/pin to:

buz_tim = pyb.Timer(8, freq=440)
buz_ch =, pyb.Timer.PWM, pin=pyb.Pin('Y2'), pulse_width=0)

To see which timers are available on which pins, consult the MicroPython quickref:

David Glaude used the following play_tone routine on Circuit Python M0 board:

import board
import pulseio
import time

speaker_pin   = board.D0  # Speaker is connected to this DIGITAL pin

# Initialize input/output pins
pwm       = pulseio.PWMOut(speaker_pin, variable_frequency=True, duty_cycle=0)

def play_tone(freq, msec):
#    print('freq = {:6.1f} msec = {:6.1f}'.format(freq, msec))
    if freq > 0:
        pwm.frequency  = int(freq)   # Set frequency
        pwm.duty_cycle = 32767  # 50% duty cycle
	time.sleep(msec*0.001)  # Play for a number of msec
    pwm.duty_cycle = 0          # Stop playing
    time.sleep(0.05)            # Delay 50 ms between notes


  • Playing RTTTL on M0 Circuit Python board.
  • Printing RTTTL decoding on any platform (no sound produced).
  • Playing RTTTL on G30DEV board.
  • RTTTL decoding library.
  • Optionnal collection of RTTTL songs to test the library.


Python Parser for Ring Tone Text Transfer Language (RTTTL)







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