.. _esp8266_quickref:

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

.. image:: img/adafruit_products_pinoutstop.jpg
    :alt: Adafruit Feather HUZZAH board
    :width: 640px

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

Below is a quick reference for ESP8266-based boards.  If it is your first time
working with this board please consider reading the following sections first:

.. toctree::
   :maxdepth: 1

   general.rst
   tutorial/index.rst

Installing MicroPython
----------------------

See the corresponding section of tutorial: :ref:`intro`. It also includes
a troubleshooting subsection.

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 :mod:`machine` module::

    import machine

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

The :mod:`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 :mod:`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('ssid', 'key') # connect to an AP
    wlan.config('mac')      # get the interface's MAC address
    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(ssid='ESP-AP') # set the SSID 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('ssid', 'key')
            while not wlan.isconnected():
                pass
        print('network config:', wlan.ifconfig())

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

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

Use the :mod:`time <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(time.ticks_ms(), start) # compute time difference

Timers
------

Virtual (RTOS-based) timers are supported. Use the :ref:`machine.Timer <machine.Timer>` class
with timer ID of -1::

    from machine import Timer

    tim = Timer(-1)
    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 :ref:`machine.Pin <machine.Pin>` class::

    from machine import Pin

    p0 = Pin(0, Pin.OUT)    # create output pin on GPIO0
    p0.on()                 # set pin to "on" (high) level
    p0.off()                # set pin to "off" (low) level
    p0.value(1)             # set pin to on/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, which correspond
to the actual GPIO pin numbers of ESP8266 chip. Note that many end-user
boards use their own adhoc pin numbering (marked e.g. D0, D1, ...). As
MicroPython supports different boards and modules, physical pin numbering
was chosen as the lowest common denominator. For mapping between board
logical pins and physical chip pins, consult your board documentation.

Note that Pin(1) and Pin(3) are REPL UART TX and RX respectively.
Also note that Pin(16) is a special pin (used for wakeup from deepsleep
mode) and may be not available for use with higher-level classes like
``Neopixel``.

There's a higher-level abstraction :ref:`machine.Signal <machine.Signal>`
which can be used to invert a pin. Useful for illuminating active-low LEDs
using ``on()`` or ``value(1)``.

UART (serial bus)
-----------------

See :ref:`machine.UART <machine.UART>`. ::

    from machine import UART
    uart = UART(0, baudrate=9600)
    uart.write('hello')
    uart.read(5) # read up to 5 bytes

Two UARTs are available. UART0 is on Pins 1 (TX) and 3 (RX). UART0 is
bidirectional, and by default is used for the REPL. UART1 is on Pins 2
(TX) and 8 (RX) however Pin 8 is used to connect the flash chip, so
UART1 is TX only.

When UART0 is attached to the REPL, all incoming chars on UART(0) go
straight to stdin so uart.read() will always return None.  Use
sys.stdin.read() if it's needed to read characters from the UART(0)
while it's also used for the REPL (or detach, read, then reattach).
When detached the UART(0) can be used for other purposes.

If there are no objects in any of the dupterm slots when the REPL is
started (on hard or soft reset) then UART(0) is automatically attached.
Without this, the only way to recover a board without a REPL would be to
completely erase and reflash (which would install the default boot.py which
attaches the REPL).

To detach the REPL from UART0, use::

    import os
    os.dupterm(None, 1)

The REPL is attached by default. If you have detached it, to reattach
it use::

    import os, machine
    uart = machine.UART(0, 115200)
    os.dupterm(uart, 1)

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 :ref:`machine.ADC <machine.ADC>` class::

    from machine import ADC

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

Software SPI bus
----------------

There are two SPI drivers. One is implemented in software (bit-banging)
and works on all pins, and is accessed via the :ref:`machine.SoftSPI <machine.SoftSPI>`
class::

    from machine import Pin, SoftSPI

    # 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 = SoftSPI(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 outputting 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


Hardware SPI bus
----------------

The hardware SPI is faster (up to 80Mhz), but only works on following pins:
``MISO`` is GPIO12, ``MOSI`` is GPIO13, and ``SCK`` is GPIO14. It has the same
methods as the bitbanging SPI class above, except for the pin parameters for the
constructor and init (as those are fixed)::

    from machine import Pin, SPI

    hspi = SPI(1, baudrate=80000000, polarity=0, phase=0)

(``SPI(0)`` is used for FlashROM and not available to users.)

I2C bus
-------

The I2C driver is implemented in software and works on all pins,
and is accessed via the :ref:`machine.I2C <machine.I2C>` class (which is an
alias of :ref:`machine.SoftI2C <machine.SoftI2C>`)::

    from machine import Pin, I2C

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

    i2c.readfrom(0x3a, 4)   # read 4 bytes from peripheral device with address 0x3a
    i2c.writeto(0x3a, '12') # write '12' to peripheral device with address 0x3a

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

Real time clock (RTC)
---------------------

See :ref:`machine.RTC <machine.RTC>` ::

    from machine import RTC

    rtc = RTC()
    rtc.datetime((2017, 8, 23, 1, 12, 48, 0, 0)) # set a specific date and time
    rtc.datetime() # get date and time

    # synchronize with ntp
    # need to be connected to wifi
    import ntptime
    ntptime.settime() # set the rtc datetime from the remote server
    rtc.datetime()    # get the date and time in UTC

.. note:: Not all methods are implemented: `RTC.now()`, `RTC.irq(handler=*) <RTC.irq>`
          (using a custom handler), `RTC.init()` and `RTC.deinit()` are
          currently not supported.

WDT (Watchdog timer)
--------------------

See :ref:`machine.WDT <machine.WDT>`. ::

    from machine import WDT

    # enable the WDT
    wdt = WDT()
    wdt.feed()

Deep-sleep mode
---------------

Connect GPIO16 to the reset pin (RST on HUZZAH).  Then the following code
can be used to sleep, wake and check the reset cause::

    import machine

    # configure RTC.ALARM0 to be able to wake the device
    rtc = machine.RTC()
    rtc.irq(trigger=rtc.ALARM0, wake=machine.DEEPSLEEP)

    # check if the device woke from a deep sleep
    if machine.reset_cause() == machine.DEEPSLEEP_RESET:
        print('woke from a deep sleep')

    # set RTC.ALARM0 to fire after 10 seconds (waking the device)
    rtc.alarm(rtc.ALARM0, 10000)

    # put the device to sleep
    machine.deepsleep()

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.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 driver
---------------

Use the ``neopixel`` module::

    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

.. 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.

For low-level driving of a NeoPixel see `machine.bitstream`.

APA102 driver
-------------

Use the ``apa102`` module::

    from machine import Pin
    from apa102 import APA102

    clock = Pin(14, Pin.OUT)     # set GPIO14 to output to drive the clock
    data = Pin(13, Pin.OUT)      # set GPIO13 to output to drive the data
    apa = APA102(clock, data, 8) # create APA102 driver on the clock and the data pin for 8 pixels
    apa[0] = (255, 255, 255, 31) # set the first pixel to white with a maximum brightness of 31
    apa.write()                  # write data to all pixels
    r, g, b, brightness = apa[0] # get first pixel colour

For low-level driving of an APA102::

    import esp
    esp.apa102_write(clock_pin, data_pin, rgbi_buf)

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)

SSD1306 driver
--------------

Driver for SSD1306 monochrome OLED displays. See tutorial :ref:`ssd1306`. ::

    from machine import Pin, I2C
    import ssd1306

    i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
    display = ssd1306.SSD1306_I2C(128, 64, i2c)

    display.text('Hello World', 0, 0, 1)
    display.show()

WebREPL (web browser interactive prompt)
----------------------------------------

WebREPL (REPL over WebSockets, accessible via a web browser) is an
experimental feature available in ESP8266 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()

The supported way to use WebREPL is by connecting to ESP8266 access point,
but the daemon is also started on STA interface if it is active, so if your
router is set up and works correctly, you may also use WebREPL while connected
to your normal Internet access point (use the ESP8266 AP connection method
if you face any issues).

Besides terminal/command prompt access, WebREPL also has provision for file
transfer (both upload and download). Web client has buttons for the
corresponding functions, or you can use command-line client ``webrepl_cli.py``
from the repository above.

See the MicroPython forum for other community-supported alternatives
to transfer files to ESP8266.
