305 lines
10 KiB
ReStructuredText
305 lines
10 KiB
ReStructuredText
.. _quickref:
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Quick reference for the ESP8266
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===============================
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.. image:: https://learn.adafruit.com/system/assets/assets/000/028/689/medium640/adafruit_products_pinoutstop.jpg
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:alt: Adafruit Feather HUZZAH board
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:width: 640px
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The Adafruit Feather HUZZAH board (image attribution: Adafruit).
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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 ``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(160000000) # set the CPU frequency to 160 MHz
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The ``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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Networking
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----------
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The ``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.mac() # get the interface's MAC adddress
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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.active(True) # activate the interface
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ap.config(essid='ESP-AP') # set the ESSID of the access point
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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 ``socket`` module can be used
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to create and use TCP/UDP sockets as usual.
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Delay and timing
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----------------
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Use the ``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(start, time.ticks_ms()) # compute time difference
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Timers
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------
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Virtual (RTOS-based) timers are supported. Use the ``machine.Timer`` class
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with timer ID of -1::
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from machine import Timer
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tim = Timer(-1)
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tim.init(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(1))
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tim.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(2))
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The period is in milliseconds.
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Pins and GPIO
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-------------
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Use the ``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.high() # set pin to high
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p0.low() # set pin to low
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p0.value(1) # set pin to 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: 0, 1, 2, 3, 4, 5, 12, 13, 14, 15, 16, which correspond
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to the actual GPIO pin numbers of ESP8266 chip. Note that many end-user
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boards use their own adhoc pin numbering (marked e.g. D0, D1, ...). As
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MicroPython supports different boards and modules, physical pin numbering
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was chosen as the lowest common denominator. For mapping between board
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logical pins and physical chip pins, consult your board documentation.
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Note that Pin(1) and Pin(3) are REPL UART TX and RX respectively.
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Also note that Pin(16) is a special pin (used for wakeup from deepsleep
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mode) and may be not available for use with higher-level classes like
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``Neopixel``.
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PWM (pulse width modulation)
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----------------------------
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PWM can be enabled on all pins except Pin(16). There is a single frequency
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for all channels, with range between 1 and 1000 (measured in Hz). The duty
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cycle is between 0 and 1023 inclusive.
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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=500, 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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ADC is available on a dedicated pin.
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Note that input voltages on the ADC pin must be between 0v and 1.0v.
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Use the ``machine.ADC`` class::
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from machine import ADC
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adc = ADC(0) # create ADC object on ADC pin
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adc.read() # read value, 0-1024
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SPI bus
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-------
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The SPI driver is implemented in software and works on all pins::
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from machine import Pin, SPI
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# construct an SPI 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 = SPI(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 outputing 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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I2C bus
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-------
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The I2C driver is implemented in software and works on all pins::
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from machine import Pin, I2C
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# construct an I2C bus
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i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
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i2c.readfrom(0x3a, 4) # read 4 bytes from slave device with address 0x3a
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i2c.writeto(0x3a, '12') # write '12' to slave 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 slave
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i2c.readfrom(0x3a, 4, stop=False) # don't send a stop bit after reading
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i2c.writeto(0x3a, buf, stop=False) # don't send a stop bit after writing
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Deep-sleep mode
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---------------
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Connect GPIO16 to the reset pin (RST on HUZZAH). Then the following code
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can be used to sleep, wake and check the reset cause::
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import machine
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# configure RTC.ALARM0 to be able to wake the device
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rtc = machine.RTC()
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rtc.irq(trigger=rtc.ALARM0, wake=machine.DEEPSLEEP)
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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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# set RTC.ALARM0 to fire after 10 seconds (waking the device)
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rtc.alarm(rtc.ALARM0, 10000)
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# put the device to sleep
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machine.deepsleep()
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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::
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from machine import Pin
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import onewire
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ow = onewire.OneWire(Pin(12)) # create a OneWire bus on GPIO12
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ow.scan() # return a list of devices on the bus
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ow.reset() # reset the bus
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ow.readbyte() # read a byte
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ow.read(5) # read 5 bytes
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ow.writebyte(0x12) # write a byte on the bus
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ow.write('123') # write bytes on the bus
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ow.select_rom(b'12345678') # select a specific device by its ROM code
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There is a specific driver for DS18B20 devices::
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import time
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ds = onewire.DS18B20(ow)
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roms = ds.scan()
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ds.convert_temp()
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time.sleep_ms(750)
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for rom in roms:
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print(ds.read_temp(rom))
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Be sure to put a 4.7k pull-up resistor on the data line. Note that
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the ``convert_temp()`` method must be called each time you want to
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sample the temperature.
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NeoPixel driver
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---------------
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Use the ``neopixel`` module::
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from machine import Pin
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from neopixel import NeoPixel
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pin = Pin(0, Pin.OUT) # set GPIO0 to output to drive NeoPixels
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np = NeoPixel(pin, 8) # create NeoPixel driver on GPIO0 for 8 pixels
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np[0] = (255, 255, 255) # set the first pixel to white
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np.write() # write data to all pixels
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r, g, b = np[0] # get first pixel colour
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For low-level driving of a NeoPixel::
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import esp
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esp.neopixel_write(pin, grb_buf, is800khz)
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WebREPL (web browser interactive prompt)
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----------------------------------------
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WebREPL (REPL over WebSockets, accessible via a web browser) is an
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experimental feature available in ESP8266 port. Download web client
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from https://github.com/micropython/webrepl , and start daemon using::
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import webrepl
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webrepl.start()
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(Release version will have it started on boot by default.)
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On a first connection, you will be prompted to set password for future
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sessions to use.
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The supported way to use WebREPL is by connecting to ESP8266 access point,
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but the daemon is also started on STA interface if it is active, so if your
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routers is set up and works correctly, you may also use it while connecting
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to your normal Internet access point (use ESP8266 AP connection method if
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face any issues).
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WebREPL is an experimental feature and a work in progress, and has known
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issues. There's also provision to transfer (both upload and download)
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files over WebREPL connection, but it has unstable status (be ready to
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reboot a module in case of issues). It still may be a practical way to
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get script files onto ESP8266, so give it a try using ``webrepl_cli.py``
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from the repository above. See forum for other community-supported
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alternatives to transfer files to ESP8266.
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