path: root/docs/esp8266/quickref.rst

.. _quickref:

Quick reference for the ESP8266
===============================

.. image:: https://learn.adafruit.com/system/assets/assets/000/028/689/medium640/adafruit_products_pinoutstop.jpg
    :alt: Adafruit Feather HUZZAH board
    :width: 640px

The Adafruit Feather HUZZAH board (image attribution: Adafruit).

General board control
---------------------

The MicroPython REPL is on UART0 (GPIO1=TX, GPIO3=RX) at baudrate 115200.
Tab-completion is useful to find out what methods an object has.
Paste mode (ctrl-E) is useful to paste a large slab of Python code into
the REPL.

The ``machine`` module::

    import machine

    machine.freq()          # get the current frequency of the CPU
    machine.freq(160000000) # set the CPU frequency to 160 MHz

The ``esp`` module::

    import esp

    esp.osdebug(None)       # turn off vendor O/S debugging messages
    esp.osdebug(0)          # redirect vendor O/S debugging messages to UART(0)

Networking
----------

The ``network`` module::

    import network

    wlan = network.WLAN(network.STA_IF) # create station interface
    wlan.active(True)       # activate the interface
    wlan.scan()             # scan for access points
    wlan.isconnected()      # check if the station is connected to an AP
    wlan.connect('essid', 'password') # connect to an AP
    wlan.mac()              # get the interface's MAC adddress
    wlan.ifconfig()         # get the interface's IP/netmask/gw/DNS addresses

    ap = network.WLAN(network.AP_IF) # create access-point interface
    ap.active(True)         # activate the interface
    ap.config(essid='ESP-AP') # set the ESSID of the access point

A useful function for connecting to your local WiFi network is::

    def do_connect():
        import network
        wlan = network.WLAN(network.STA_IF)
        wlan.active(True)
        if not wlan.isconnected():
            print('connecting to network...')
            wlan.connect('essid', 'password')
            while not wlan.isconnected():
                pass
        print('network config:', wlan.ifconfig())

Once the network is established the ``socket`` module can be used
to create and use TCP/UDP sockets as usual.

Delay and timing
----------------

Use the ``time`` module::

    import time

    time.sleep(1)           # sleep for 1 second
    time.sleep_ms(500)      # sleep for 500 milliseconds
    time.sleep_us(10)       # sleep for 10 microseconds
    start = time.ticks_ms() # get millisecond counter
    delta = time.ticks_diff(start, time.ticks_ms()) # compute time difference

Timers
------

Use the ``machine.Timer`` class::

    from machine import Timer

    tim = Timer(0)
    tim.init(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(1))
    tim.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(2))

The period is in milliseconds.

Pins and GPIO
-------------

Use the ``machine.Pin`` class::

    from machine import Pin

    p0 = Pin(0, Pin.OUT)    # create output pin on GPIO0
    p0.high()               # set pin to high
    p0.low()                # set pin to low
    p0.value(1)             # set pin to high

    p2 = Pin(2, Pin.IN)     # create input pin on GPIO2
    print(p2.value())       # get value, 0 or 1

    p4 = Pin(4, Pin.IN, Pin.PULL_UP) # enable internal pull-up resistor
    p5 = Pin(5, Pin.OUT, value=1) # set pin high on creation

Available pins are: 0, 1, 2, 3, 4, 5, 12, 13, 14, 15, 16.
Note that Pin(1) and Pin(3) are REPL UART TX and RX respectively.

PWM (pulse width modulation)
----------------------------

PWM can be enabled on all pins except Pin(16).  There is a single frequency
for all channels, with range between 1 and 1000 (measured in Hz).  The duty
cycle is between 0 and 1023 inclusive.

Use the ``machine.PWM`` class::

    from machine import Pin, PWM

    pwm0 = PWM(Pin(0))      # create PWM object from a pin
    pwm0.freq()             # get current frequency
    pwm0.freq(1000)         # set frequency
    pwm0.duty()             # get current duty cycle
    pwm0.duty(200)          # set duty cycle
    pwm0.deinit()           # turn off PWM on the pin

    pwm2 = PWM(Pin(2), freq=500, duty=512) # create and configure in one go

ADC (analog to digital conversion)
----------------------------------

ADC is available on a dedicated pin.
Note that input voltages on the ADC pin must be between 0v and 1.0v.

Use the ``machine.ADC`` class::

    from machine import ADC

    adc = ADC(0)            # create ADC object on ADC pin
    adc.read()              # read value, 0-1024

SPI bus
-------

The SPI driver is implemented in software and works on all pins::

    from machine import Pin, SPI

    # construct an SPI bus on the given pins
    # polarity is the idle state of SCK
    # phase=0 means sample on the first edge of SCK, phase=1 means the second
    spi = SPI(baudrate=100000, polarity=1, phase=0, sck=Pin(0), mosi=Pin(2), miso=Pin(4))

    spi.init(baudrate=200000) # set the baudrate

    spi.read(10)            # read 10 bytes on MISO
    spi.read(10, 0xff)      # read 10 bytes while outputing 0xff on MOSI

    buf = bytearray(50)     # create a buffer
    spi.readinto(buf)       # read into the given buffer (reads 50 bytes in this case)
    spi.readinto(buf, 0xff) # read into the given buffer and output 0xff on MOSI

    spi.write(b'12345')     # write 5 bytes on MOSI

    buf = bytearray(4)      # create a buffer
    spi.write_readinto(b'1234', buf) # write to MOSI and read from MISO into the buffer
    spi.write_readinto(buf, buf) # write buf to MOSI and read MISO back into buf

I2C bus
-------

The I2C driver is implemented in software and works on all pins::

    from machine import Pin, I2C

    # construct an I2C bus
    i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)

    i2c.writeto(0x3a, '12') # write '12' to slave device with address 0x3a

    buf = bytearray(10)     # create a buffer with 10 bytes
    i2c.writeto(0x3a, buf)  # write the given buffer to the slave

    i2c.writeto(0x3a, buf, stop=False) # don't send a stop bit after writing

Note that reading is not yet implemented.

OneWire driver
--------------

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.read_byte()          # read a byte
    ow.read_bytes(5)        # read 5 bytes
    ow.write_byte(0x12)     # write a byte on the bus
    ow.write_bytes('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 DS18B20 devices::

    import time
    ds = onewire.DS18B20(ow)
    roms = ds.scan()
    ds.start_measure()
    time.sleep_ms(750)
    for rom in roms:
        print(ds.get_temp(rom))

Be sure to put a 4.7k pull-up resistor on the data line.

NeoPixel driver
---------------

Use the ``neopixel`` module::

    from machine import Pin
    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

    neopixel.demo(np)       # run a demo

For low-level driving of a NeoPixel::

    import esp
    esp.neopixel_write(pin, grb_buf, is800khz)