pulseio – Support for individual pulse based protocols

The pulseio module contains classes to provide access to basic pulse IO. Individual pulses are commonly used in infrared remotes and in DHT temperature sensors.

All classes change hardware state and should be deinitialized when they are no longer needed if the program continues after use. To do so, either call deinit() or use a context manager. See Lifetime and ContextManagers for more info.

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class pulseio.PulseIn(pin: microcontroller.Pin, maxlen: int = 2, *, idle_state: bool = False)

Measure a series of active and idle pulses. This is commonly used in infrared receivers and low cost temperature sensors (DHT). The pulsed signal consists of timed active and idle periods. Unlike PWM, there is no set duration for active and idle pairs.

Create a PulseIn object associated with the given pin. The object acts as a read-only sequence of pulse lengths with a given max length. When it is active, new pulse lengths are added to the end of the list. When there is no more room (len() == maxlen) the oldest pulse length is removed to make room.

Parameters
  • pin (Pin) – Pin to read pulses from.

  • maxlen (int) – Maximum number of pulse durations to store at once

  • idle_state (bool) – Idle state of the pin. At start and after resume the first recorded pulse will the opposite state from idle.

Read a short series of pulses:

import pulseio
import board

pulses = pulseio.PulseIn(board.D7)

# Wait for an active pulse
while len(pulses) == 0:
    pass
# Pause while we do something with the pulses
pulses.pause()

# Print the pulses. pulses[0] is an active pulse unless the length
# reached max length and idle pulses are recorded.
print(pulses)

# Clear the rest
pulses.clear()

# Resume with an 80 microsecond active pulse
pulses.resume(80)
maxlen :int

The maximum length of the PulseIn. When len() is equal to maxlen, it is unclear which pulses are active and which are idle.

paused :bool

True when pulse capture is paused as a result of pause() or an error during capture such as a signal that is too fast.

deinit(self)None

Deinitialises the PulseIn and releases any hardware resources for reuse.

__enter__(self)PulseIn

No-op used by Context Managers.

__exit__(self)None

Automatically deinitializes the hardware when exiting a context. See Lifetime and ContextManagers for more info.

pause(self)None

Pause pulse capture

resume(self, trigger_duration: int = 0)None

Resumes pulse capture after an optional trigger pulse.

Warning

Using trigger pulse with a device that drives both high and low signals risks a short. Make sure your device is open drain (only drives low) when using a trigger pulse. You most likely added a “pull-up” resistor to your circuit to do this.

Parameters

trigger_duration (int) – trigger pulse duration in microseconds

clear(self)None

Clears all captured pulses

popleft(self)int

Removes and returns the oldest read pulse.

__bool__(self)bool
__len__(self)int

Returns the number of pulse durations currently stored.

This allows you to:

pulses = pulseio.PulseIn(pin)
print(len(pulses))
__getitem__(self, index: int)Optional[int]

Returns the value at the given index or values in slice.

This allows you to:

pulses = pulseio.PulseIn(pin)
print(pulses[0])
class pulseio.PulseOut(pin: microcontroller.Pin, *, frequency: int = 38000, duty_cycle: int = 1 << 15)

Pulse PWM “carrier” output on and off. This is commonly used in infrared remotes. The pulsed signal consists of timed on and off periods. Unlike PWM, there is no set duration for on and off pairs.

Create a PulseOut object associated with the given pin.

Parameters
  • pin (Pin) – Signal output pin

  • frequency (int) – Carrier signal frequency in Hertz

  • duty_cycle (int) – 16-bit duty cycle of carrier frequency (0 - 65536)

For backwards compatibility, pin may be a PWMOut object used as the carrier. This compatibility will be removed in CircuitPython 8.0.0.

Send a short series of pulses:

import array
import pulseio
import pwmio
import board

# 50% duty cycle at 38kHz.
pwm = pulseio.PulseOut(board.D13, frequency=38000, duty_cycle=32768)
#                             on   off     on    off    on
pulses = array.array('H', [65000, 1000, 65000, 65000, 1000])
pulse.send(pulses)

# Modify the array of pulses.
pulses[0] = 200
pulse.send(pulses)
deinit(self)None

Deinitialises the PulseOut and releases any hardware resources for reuse.

__enter__(self)PulseOut

No-op used by Context Managers.

__exit__(self)None

Automatically deinitializes the hardware when exiting a context. See Lifetime and ContextManagers for more info.

send(self, pulses: _typing.ReadableBuffer)None

Pulse alternating on and off durations in microseconds starting with on. pulses must be an array.array with data type ‘H’ for unsigned halfword (two bytes).

This method waits until the whole array of pulses has been sent and ensures the signal is off afterwards.

Parameters

pulses (array.array) – pulse durations in microseconds