class RMT – Remote Controller
The RMT (Remote Control) module is primarily designed to send and receive infrared remote control signals that use on-off-keying of a carrier frequency, but due to its design it can be used to generate various types of signals.
Quick Usage Example: sending
import machine
# create a RMT object for transmission
rmt = machine.RMT(channel=3, gpio="P20", tx_idle_level=0)
# create series of bits to send
data = (1,0,1,0,1,0,1,0,1)
# define duration of the bits, time unit depends on the selected RMT channel
duration = 10000
# send the signal
rmt.send_pulses(duration, data)
Quick Usage Example: receiving
import machine
# create a RMT object
rmt = machine.RMT(channel=3)
# Configure RTM for receiving
rmt.init(gpio="P20", rx_idle_threshold=12000)
# wait for any number of pulses until one longer than rx_idle_threshold
data = rmt.recv_pulses()
Constructors
Construct an RMT object on the given channel. channel
can be 2-7. With no additional parameters, the RMT object is created but not initialised. If extra arguments are given, the RMT is initialised for transmission or reception. See init
for parameters of initialisation.
The resolution which a pulse can be sent/received depends on the selected channel:
Channel | Resolution | Maximum Pulse Width | |
---|---|---|---|
0 | Used by on-board LED | ||
1 | Used by pycom.pulses_get() |
||
2 | 100nS | 3.2768 ms | |
3 | 100nS | 3.2768 ms | |
4 | 1000nS | 32.768 ms | |
5 | 1000nS | 32.768 ms | |
6 | 3125nS | 102.4 ms | |
7 | 3125nS | 102.4 ms |
Methods
Initialise the RMT peripheral with the given parameters:
gpio
is the GPIO Pin to use.rx_idle_threshold
is the maximum duration of a valid pulse. The represented time unit (resolution) depends on the selected channel, value can be 0-65535.rx_filter_threshold
is the minimum duration of a valid pulse. The represented time unit (resolution) depends on the selected channel, value can be 0-31.tx_idle_level
is the output signal's level after the transmission is finished, can beRMT.HIGH orRMT.LOW .tx_carrier
is the modulation of the pulses to send.
Either rx_idle_threshold
or tx_idle_level
must be defined, both cannot be given at the same time because a channel can be configured in RX or TX mode only.
rx_filter_threshold
is not mandatory parameter. If not given then all pulses are accepted with duration less than rx_idle_threshold
.
tx_carrier
is not mandatory parameters. If not given no modulation is used on the sent pulses.
The tx_carrier
parameter is a tuple with the following structure:
carrier_freq_hz
is the carrier's frequency in Hz.carrier_duty_percent
is the duty percent of the carrier's signal, can be 0%-100%.carrier_level
is the level of the pulse to modulate, can beRMT.HIGH orRMT.LOW .
Deinitialise the RMT object.
If an RMT object needs to be reconfigured from RX/TX to TX/RX, then either first deinit()
must be called or the init()
again with the desired configuration.
Reads in pulses from the GPIO pin.
pulses
if not specified, this function will keep reading pulses until therx_idle_threshold
is exceeded. If it is specified this function will return the exactly that number of pulses, ignoring anything shorter thanrx_filter_threshold
or longer thanrx_idle_threshold
.timeout
is specified, this function will return if the first pulse does not occur withintimeout
microseconds. If not specified, it will wait indefinitely.
Return value: Tuple of items with the following structure: (level, duration):
level
represents the level of the received bit/pulse, can be 0 or 1.duration
represents the duration of the received pulse, the time unit (resolution) depends on the selected channel.
Maximum of 128 pulses can be received in a row without receiving "idle" signal. If the incoming pulse sequence contains more than 128 pulses the rest is dropped and the receiver waits for another sequence of pulses.
The pulses_get
function can be called to receive more than 128 pulses, however the above mentioned limitation should be kept in mind when evaluating the received data.
Generates pulses as defined by the parameters below
duration
represents the duration of the pulses to be sent, the time unit (resolution) depends on the selected channel.data
Tuple that represents the sequence of pulses to be sent, must be composed of 0 or 1 elements.start_level
defines the state (HIGH/LOW) of the first pulse given byduration
ifdata
is not given.
data
must be a tuple and duration
can be a tuple or a single number, with
data
being optional. In the case that only duration
is provided, it must
be a tuple and you must also provide start_level
which will dictate the
level of the first duration, the signal level then toggles between each duration value. If data
is provided and duration
is a single number, each pulse
in data
will have have an equal length as set by duration
. If data
and duration
are provided as tuples, they must be of the same number of
elements, with each pulse lasting its matching duration.
wait_tx_done
:
False
: Allows the function to send asynchronosly without waiting for the transmission to be done.
True
: will wait for transmission to be done
Constants
Defines the level of the pulse.