c737cde947
Anywhere a module is mentioned, use its "non-u" name for consistency. The "import module" vs "import umodule" is something of a FAQ, and this commit intends to help clear that up. As a first approximation MicroPython is Python, and so imports should work the same as Python and use the same name, to a first approximation. The u-version of a module is a detail that can be learned later on, when the user wants to understand more and have finer control over importing. Existing Python code should just work, as much as it is possible to do that within the constraints of embedded systems, and the MicroPython documentation should match the idiomatic way to write Python code. With universal weak links for modules (via MICROPY_MODULE_WEAK_LINKS) users can consistently use "import foo" across all ports (with the exception of the minimal ports). And the ability to override/extend via "foo.py" continues to work well. Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
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ReStructuredText
.. _esp32_quickref:
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Quick reference for the ESP32
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=============================
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.. image:: img/esp32.jpg
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:alt: ESP32 board
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:width: 640px
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The Espressif ESP32 Development Board (image attribution: Adafruit).
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Below is a quick reference for ESP32-based boards. If it is your first time
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working with this board it may be useful to get an overview of the microcontroller:
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.. toctree::
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:maxdepth: 1
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general.rst
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tutorial/intro.rst
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Installing MicroPython
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----------------------
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See the corresponding section of tutorial: :ref:`esp32_intro`. It also includes
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a troubleshooting subsection.
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General board control
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---------------------
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The MicroPython REPL is on UART0 (GPIO1=TX, GPIO3=RX) at baudrate 115200.
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Tab-completion is useful to find out what methods an object has.
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Paste mode (ctrl-E) is useful to paste a large slab of Python code into
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the REPL.
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The :mod:`machine` module::
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import machine
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machine.freq() # get the current frequency of the CPU
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machine.freq(240000000) # set the CPU frequency to 240 MHz
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The :mod:`esp` module::
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import esp
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esp.osdebug(None) # turn off vendor O/S debugging messages
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esp.osdebug(0) # redirect vendor O/S debugging messages to UART(0)
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# low level methods to interact with flash storage
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esp.flash_size()
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esp.flash_user_start()
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esp.flash_erase(sector_no)
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esp.flash_write(byte_offset, buffer)
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esp.flash_read(byte_offset, buffer)
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The :mod:`esp32` module::
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import esp32
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esp32.hall_sensor() # read the internal hall sensor
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esp32.raw_temperature() # read the internal temperature of the MCU, in Fahrenheit
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esp32.ULP() # access to the Ultra-Low-Power Co-processor
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Note that the temperature sensor in the ESP32 will typically read higher than
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ambient due to the IC getting warm while it runs. This effect can be minimised
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by reading the temperature sensor immediately after waking up from sleep.
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Networking
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----------
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The :mod:`network` module::
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import network
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wlan = network.WLAN(network.STA_IF) # create station interface
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wlan.active(True) # activate the interface
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wlan.scan() # scan for access points
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wlan.isconnected() # check if the station is connected to an AP
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wlan.connect('essid', 'password') # connect to an AP
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wlan.config('mac') # get the interface's MAC address
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wlan.ifconfig() # get the interface's IP/netmask/gw/DNS addresses
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ap = network.WLAN(network.AP_IF) # create access-point interface
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ap.config(essid='ESP-AP') # set the ESSID of the access point
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ap.config(max_clients=10) # set how many clients can connect to the network
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ap.active(True) # activate the interface
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A useful function for connecting to your local WiFi network is::
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def do_connect():
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import network
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wlan = network.WLAN(network.STA_IF)
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wlan.active(True)
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if not wlan.isconnected():
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print('connecting to network...')
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wlan.connect('essid', 'password')
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while not wlan.isconnected():
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pass
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print('network config:', wlan.ifconfig())
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Once the network is established the :mod:`socket <socket>` module can be used
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to create and use TCP/UDP sockets as usual, and the ``urequests`` module for
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convenient HTTP requests.
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After a call to ``wlan.connect()``, the device will by default retry to connect
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**forever**, even when the authentication failed or no AP is in range.
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``wlan.status()`` will return ``network.STAT_CONNECTING`` in this state until a
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connection succeeds or the interface gets disabled. This can be changed by
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calling ``wlan.config(reconnects=n)``, where n are the number of desired reconnect
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attempts (0 means it won't retry, -1 will restore the default behaviour of trying
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to reconnect forever).
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Delay and timing
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----------------
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Use the :mod:`time <time>` module::
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import time
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time.sleep(1) # sleep for 1 second
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time.sleep_ms(500) # sleep for 500 milliseconds
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time.sleep_us(10) # sleep for 10 microseconds
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start = time.ticks_ms() # get millisecond counter
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delta = time.ticks_diff(time.ticks_ms(), start) # compute time difference
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Timers
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------
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The ESP32 port has four hardware timers. Use the :ref:`machine.Timer <machine.Timer>` class
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with a timer ID from 0 to 3 (inclusive)::
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from machine import Timer
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tim0 = Timer(0)
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tim0.init(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(0))
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tim1 = Timer(1)
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tim1.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(1))
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The period is in milliseconds.
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Virtual timers are not currently supported on this port.
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.. _Pins_and_GPIO:
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Pins and GPIO
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-------------
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Use the :ref:`machine.Pin <machine.Pin>` class::
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from machine import Pin
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p0 = Pin(0, Pin.OUT) # create output pin on GPIO0
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p0.on() # set pin to "on" (high) level
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p0.off() # set pin to "off" (low) level
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p0.value(1) # set pin to on/high
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p2 = Pin(2, Pin.IN) # create input pin on GPIO2
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print(p2.value()) # get value, 0 or 1
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p4 = Pin(4, Pin.IN, Pin.PULL_UP) # enable internal pull-up resistor
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p5 = Pin(5, Pin.OUT, value=1) # set pin high on creation
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Available Pins are from the following ranges (inclusive): 0-19, 21-23, 25-27, 32-39.
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These correspond to the actual GPIO pin numbers of ESP32 chip. Note that many
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end-user boards use their own adhoc pin numbering (marked e.g. D0, D1, ...).
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For mapping between board logical pins and physical chip pins consult your board
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documentation.
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Notes:
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* Pins 1 and 3 are REPL UART TX and RX respectively
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* Pins 6, 7, 8, 11, 16, and 17 are used for connecting the embedded flash,
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and are not recommended for other uses
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* Pins 34-39 are input only, and also do not have internal pull-up resistors
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* The pull value of some pins can be set to ``Pin.PULL_HOLD`` to reduce power
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consumption during deepsleep.
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There's a higher-level abstraction :ref:`machine.Signal <machine.Signal>`
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which can be used to invert a pin. Useful for illuminating active-low LEDs
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using ``on()`` or ``value(1)``.
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UART (serial bus)
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-----------------
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See :ref:`machine.UART <machine.UART>`. ::
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from machine import UART
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uart1 = UART(1, baudrate=9600, tx=33, rx=32)
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uart1.write('hello') # write 5 bytes
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uart1.read(5) # read up to 5 bytes
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The ESP32 has three hardware UARTs: UART0, UART1 and UART2.
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They each have default GPIO assigned to them, however depending on your
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ESP32 variant and board, these pins may conflict with embedded flash,
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onboard PSRAM or peripherals.
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Any GPIO can be used for hardware UARTs using the GPIO matrix, so to avoid
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conflicts simply provide ``tx`` and ``rx`` pins when constructing. The default
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pins listed below.
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===== ===== ===== =====
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\ UART0 UART1 UART2
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===== ===== ===== =====
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tx 1 10 17
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rx 3 9 16
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===== ===== ===== =====
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PWM (pulse width modulation)
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----------------------------
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PWM can be enabled on all output-enabled pins. The base frequency can
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range from 1Hz to 40MHz but there is a tradeoff; as the base frequency
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*increases* the duty resolution *decreases*. See
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`LED Control <https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/ledc.html>`_
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for more details.
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Currently the duty cycle has to be in the range of 0-1023.
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Use the ``machine.PWM`` class::
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from machine import Pin, PWM
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pwm0 = PWM(Pin(0)) # create PWM object from a pin
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pwm0.freq() # get current frequency
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pwm0.freq(1000) # set frequency
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pwm0.duty() # get current duty cycle
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pwm0.duty(200) # set duty cycle
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pwm0.deinit() # turn off PWM on the pin
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pwm2 = PWM(Pin(2), freq=20000, duty=512) # create and configure in one go
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ADC (analog to digital conversion)
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----------------------------------
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On the ESP32 ADC functionality is available on Pins 32-39. Note that, when
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using the default configuration, input voltages on the ADC pin must be between
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0.0v and 1.0v (anything above 1.0v will just read as 4095). Attenuation must
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be applied in order to increase this usable voltage range.
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Use the :ref:`machine.ADC <machine.ADC>` class::
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from machine import ADC
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adc = ADC(Pin(32)) # create ADC object on ADC pin
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adc.read() # read value, 0-4095 across voltage range 0.0v - 1.0v
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adc.atten(ADC.ATTN_11DB) # set 11dB input attenuation (voltage range roughly 0.0v - 3.6v)
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adc.width(ADC.WIDTH_9BIT) # set 9 bit return values (returned range 0-511)
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adc.read() # read value using the newly configured attenuation and width
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ESP32 specific ADC class method reference:
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.. method:: ADC.atten(attenuation)
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This method allows for the setting of the amount of attenuation on the
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input of the ADC. This allows for a wider possible input voltage range,
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at the cost of accuracy (the same number of bits now represents a wider
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range). The possible attenuation options are:
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- ``ADC.ATTN_0DB``: 0dB attenuation, gives a maximum input voltage
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of 1.00v - this is the default configuration
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- ``ADC.ATTN_2_5DB``: 2.5dB attenuation, gives a maximum input voltage
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of approximately 1.34v
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- ``ADC.ATTN_6DB``: 6dB attenuation, gives a maximum input voltage
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of approximately 2.00v
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- ``ADC.ATTN_11DB``: 11dB attenuation, gives a maximum input voltage
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of approximately 3.6v
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.. Warning::
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Despite 11dB attenuation allowing for up to a 3.6v range, note that the
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absolute maximum voltage rating for the input pins is 3.6v, and so going
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near this boundary may be damaging to the IC!
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.. method:: ADC.width(width)
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This method allows for the setting of the number of bits to be utilised
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and returned during ADC reads. Possible width options are:
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- ``ADC.WIDTH_9BIT``: 9 bit data
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- ``ADC.WIDTH_10BIT``: 10 bit data
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- ``ADC.WIDTH_11BIT``: 11 bit data
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- ``ADC.WIDTH_12BIT``: 12 bit data - this is the default configuration
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Software SPI bus
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----------------
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Software SPI (using bit-banging) works on all pins, and is accessed via the
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:ref:`machine.SoftSPI <machine.SoftSPI>` class::
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from machine import Pin, SoftSPI
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# construct a SoftSPI bus on the given pins
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# polarity is the idle state of SCK
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# phase=0 means sample on the first edge of SCK, phase=1 means the second
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spi = SoftSPI(baudrate=100000, polarity=1, phase=0, sck=Pin(0), mosi=Pin(2), miso=Pin(4))
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spi.init(baudrate=200000) # set the baudrate
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spi.read(10) # read 10 bytes on MISO
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spi.read(10, 0xff) # read 10 bytes while outputting 0xff on MOSI
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buf = bytearray(50) # create a buffer
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spi.readinto(buf) # read into the given buffer (reads 50 bytes in this case)
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spi.readinto(buf, 0xff) # read into the given buffer and output 0xff on MOSI
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spi.write(b'12345') # write 5 bytes on MOSI
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buf = bytearray(4) # create a buffer
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spi.write_readinto(b'1234', buf) # write to MOSI and read from MISO into the buffer
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spi.write_readinto(buf, buf) # write buf to MOSI and read MISO back into buf
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.. Warning::
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Currently *all* of ``sck``, ``mosi`` and ``miso`` *must* be specified when
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initialising Software SPI.
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Hardware SPI bus
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----------------
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There are two hardware SPI channels that allow faster transmission
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rates (up to 80Mhz). These may be used on any IO pins that support the
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required direction and are otherwise unused (see :ref:`Pins_and_GPIO`)
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but if they are not configured to their default pins then they need to
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pass through an extra layer of GPIO multiplexing, which can impact
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their reliability at high speeds. Hardware SPI channels are limited
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to 40MHz when used on pins other than the default ones listed below.
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===== =========== ============
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\ HSPI (id=1) VSPI (id=2)
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===== =========== ============
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sck 14 18
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mosi 13 23
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miso 12 19
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===== =========== ============
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Hardware SPI is accessed via the :ref:`machine.SPI <machine.SPI>` class and
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has the same methods as software SPI above::
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from machine import Pin, SPI
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hspi = SPI(1, 10000000)
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hspi = SPI(1, 10000000, sck=Pin(14), mosi=Pin(13), miso=Pin(12))
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vspi = SPI(2, baudrate=80000000, polarity=0, phase=0, bits=8, firstbit=0, sck=Pin(18), mosi=Pin(23), miso=Pin(19))
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Software I2C bus
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----------------
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Software I2C (using bit-banging) works on all output-capable pins, and is
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accessed via the :ref:`machine.SoftI2C <machine.SoftI2C>` class::
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from machine import Pin, SoftI2C
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i2c = SoftI2C(scl=Pin(5), sda=Pin(4), freq=100000)
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i2c.scan() # scan for devices
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i2c.readfrom(0x3a, 4) # read 4 bytes from device with address 0x3a
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i2c.writeto(0x3a, '12') # write '12' to device with address 0x3a
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buf = bytearray(10) # create a buffer with 10 bytes
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i2c.writeto(0x3a, buf) # write the given buffer to the peripheral
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Hardware I2C bus
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----------------
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There are two hardware I2C peripherals with identifiers 0 and 1. Any available
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output-capable pins can be used for SCL and SDA but the defaults are given
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below.
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===== =========== ============
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\ I2C(0) I2C(1)
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===== =========== ============
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scl 18 25
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sda 19 26
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===== =========== ============
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The driver is accessed via the :ref:`machine.I2C <machine.I2C>` class and
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has the same methods as software I2C above::
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from machine import Pin, I2C
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i2c = I2C(0)
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i2c = I2C(1, scl=Pin(5), sda=Pin(4), freq=400000)
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I2S bus
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-------
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See :ref:`machine.I2S <machine.I2S>`. ::
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from machine import I2S, Pin
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i2s = I2S(0, sck=Pin(13), ws=Pin(14), sd=Pin(34), mode=I2S.TX, bits=16, format=I2S.STEREO, rate=44100, ibuf=40000) # create I2S object
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i2s.write(buf) # write buffer of audio samples to I2S device
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i2s = I2S(1, sck=Pin(33), ws=Pin(25), sd=Pin(32), mode=I2S.RX, bits=16, format=I2S.MONO, rate=22050, ibuf=40000) # create I2S object
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i2s.readinto(buf) # fill buffer with audio samples from I2S device
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The I2S class is currently available as a Technical Preview. During the preview period, feedback from
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users is encouraged. Based on this feedback, the I2S class API and implementation may be changed.
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ESP32 has two I2S buses with id=0 and id=1
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Real time clock (RTC)
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---------------------
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See :ref:`machine.RTC <machine.RTC>` ::
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from machine import RTC
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rtc = RTC()
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rtc.datetime((2017, 8, 23, 1, 12, 48, 0, 0)) # set a specific date and time
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rtc.datetime() # get date and time
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WDT (Watchdog timer)
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--------------------
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See :ref:`machine.WDT <machine.WDT>`. ::
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from machine import WDT
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# enable the WDT with a timeout of 5s (1s is the minimum)
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wdt = WDT(timeout=5000)
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wdt.feed()
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Deep-sleep mode
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---------------
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The following code can be used to sleep, wake and check the reset cause::
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import machine
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# check if the device woke from a deep sleep
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if machine.reset_cause() == machine.DEEPSLEEP_RESET:
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print('woke from a deep sleep')
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# put the device to sleep for 10 seconds
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machine.deepsleep(10000)
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Notes:
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* Calling ``deepsleep()`` without an argument will put the device to sleep
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indefinitely
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* A software reset does not change the reset cause
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* There may be some leakage current flowing through enabled internal pullups.
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To further reduce power consumption it is possible to disable the internal pullups::
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p1 = Pin(4, Pin.IN, Pin.PULL_HOLD)
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After leaving deepsleep it may be necessary to un-hold the pin explicitly (e.g. if
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it is an output pin) via::
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p1 = Pin(4, Pin.OUT, None)
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SD card
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-------
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See :ref:`machine.SDCard <machine.SDCard>`. ::
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import machine, os
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# Slot 2 uses pins sck=18, cs=5, miso=19, mosi=23
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sd = machine.SDCard(slot=2)
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os.mount(sd, "/sd") # mount
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os.listdir('/sd') # list directory contents
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os.umount('/sd') # eject
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RMT
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---
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The RMT is ESP32-specific and allows generation of accurate digital pulses with
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12.5ns resolution. See :ref:`esp32.RMT <esp32.RMT>` for details. Usage is::
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import esp32
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from machine import Pin
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r = esp32.RMT(0, pin=Pin(18), clock_div=8)
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r # RMT(channel=0, pin=18, source_freq=80000000, clock_div=8)
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# The channel resolution is 100ns (1/(source_freq/clock_div)).
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r.write_pulses((1, 20, 2, 40), start=0) # Send 0 for 100ns, 1 for 2000ns, 0 for 200ns, 1 for 4000ns
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OneWire driver
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--------------
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The OneWire driver is implemented in software and works on all pins::
|
|
|
|
from machine import Pin
|
|
import onewire
|
|
|
|
ow = onewire.OneWire(Pin(12)) # create a OneWire bus on GPIO12
|
|
ow.scan() # return a list of devices on the bus
|
|
ow.reset() # reset the bus
|
|
ow.readbyte() # read a byte
|
|
ow.writebyte(0x12) # write a byte on the bus
|
|
ow.write('123') # write bytes on the bus
|
|
ow.select_rom(b'12345678') # select a specific device by its ROM code
|
|
|
|
There is a specific driver for DS18S20 and DS18B20 devices::
|
|
|
|
import time, ds18x20
|
|
ds = ds18x20.DS18X20(ow)
|
|
roms = ds.scan()
|
|
ds.convert_temp()
|
|
time.sleep_ms(750)
|
|
for rom in roms:
|
|
print(ds.read_temp(rom))
|
|
|
|
Be sure to put a 4.7k pull-up resistor on the data line. Note that
|
|
the ``convert_temp()`` method must be called each time you want to
|
|
sample the temperature.
|
|
|
|
NeoPixel and APA106 driver
|
|
--------------------------
|
|
|
|
Use the ``neopixel`` and ``apa106`` modules::
|
|
|
|
from machine import Pin
|
|
from neopixel import NeoPixel
|
|
|
|
pin = Pin(0, Pin.OUT) # set GPIO0 to output to drive NeoPixels
|
|
np = NeoPixel(pin, 8) # create NeoPixel driver on GPIO0 for 8 pixels
|
|
np[0] = (255, 255, 255) # set the first pixel to white
|
|
np.write() # write data to all pixels
|
|
r, g, b = np[0] # get first pixel colour
|
|
|
|
|
|
The APA106 driver extends NeoPixel, but internally uses a different colour order::
|
|
|
|
from apa106 import APA106
|
|
ap = APA106(pin, 8)
|
|
r, g, b = ap[0]
|
|
|
|
For low-level driving of a NeoPixel::
|
|
|
|
import esp
|
|
esp.neopixel_write(pin, grb_buf, is800khz)
|
|
|
|
.. Warning::
|
|
By default ``NeoPixel`` is configured to control the more popular *800kHz*
|
|
units. It is possible to use alternative timing to control other (typically
|
|
400kHz) devices by passing ``timing=0`` when constructing the
|
|
``NeoPixel`` object.
|
|
|
|
APA102 (DotStar) uses a different driver as it has an additional clock pin.
|
|
|
|
Capacitive touch
|
|
----------------
|
|
|
|
Use the ``TouchPad`` class in the ``machine`` module::
|
|
|
|
from machine import TouchPad, Pin
|
|
|
|
t = TouchPad(Pin(14))
|
|
t.read() # Returns a smaller number when touched
|
|
|
|
``TouchPad.read`` returns a value relative to the capacitive variation. Small numbers (typically in
|
|
the *tens*) are common when a pin is touched, larger numbers (above *one thousand*) when
|
|
no touch is present. However the values are *relative* and can vary depending on the board
|
|
and surrounding composition so some calibration may be required.
|
|
|
|
There are ten capacitive touch-enabled pins that can be used on the ESP32: 0, 2, 4, 12, 13
|
|
14, 15, 27, 32, 33. Trying to assign to any other pins will result in a ``ValueError``.
|
|
|
|
Note that TouchPads can be used to wake an ESP32 from sleep::
|
|
|
|
import machine
|
|
from machine import TouchPad, Pin
|
|
import esp32
|
|
|
|
t = TouchPad(Pin(14))
|
|
t.config(500) # configure the threshold at which the pin is considered touched
|
|
esp32.wake_on_touch(True)
|
|
machine.lightsleep() # put the MCU to sleep until a touchpad is touched
|
|
|
|
For more details on touchpads refer to `Espressif Touch Sensor
|
|
<https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/touch_pad.html>`_.
|
|
|
|
|
|
DHT driver
|
|
----------
|
|
|
|
The DHT driver is implemented in software and works on all pins::
|
|
|
|
import dht
|
|
import machine
|
|
|
|
d = dht.DHT11(machine.Pin(4))
|
|
d.measure()
|
|
d.temperature() # eg. 23 (°C)
|
|
d.humidity() # eg. 41 (% RH)
|
|
|
|
d = dht.DHT22(machine.Pin(4))
|
|
d.measure()
|
|
d.temperature() # eg. 23.6 (°C)
|
|
d.humidity() # eg. 41.3 (% RH)
|
|
|
|
WebREPL (web browser interactive prompt)
|
|
----------------------------------------
|
|
|
|
WebREPL (REPL over WebSockets, accessible via a web browser) is an
|
|
experimental feature available in ESP32 port. Download web client
|
|
from https://github.com/micropython/webrepl (hosted version available
|
|
at http://micropython.org/webrepl), and configure it by executing::
|
|
|
|
import webrepl_setup
|
|
|
|
and following on-screen instructions. After reboot, it will be available
|
|
for connection. If you disabled automatic start-up on boot, you may
|
|
run configured daemon on demand using::
|
|
|
|
import webrepl
|
|
webrepl.start()
|
|
|
|
# or, start with a specific password
|
|
webrepl.start(password='mypass')
|
|
|
|
The WebREPL daemon listens on all active interfaces, which can be STA or
|
|
AP. This allows you to connect to the ESP32 via a router (the STA
|
|
interface) or directly when connected to its access point.
|
|
|
|
In addition to terminal/command prompt access, WebREPL also has provision
|
|
for file transfer (both upload and download). The web client has buttons for
|
|
the corresponding functions, or you can use the command-line client
|
|
``webrepl_cli.py`` from the repository above.
|
|
|
|
See the MicroPython forum for other community-supported alternatives
|
|
to transfer files to an ESP32 board.
|