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Paul Sokolovsky authoredPaul Sokolovsky authored
quickref.rst NaN GiB
.. _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.config('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
------
Virtual (RTOS-based) timers are supported. Use the ``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 ``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, 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``.
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.readfrom(0x3a, 4) # read 4 bytes from slave device with address 0x3a
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
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.read(5) # read 5 bytes
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 DS18B20 devices::
import time
ds = onewire.DS18B20(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
For low-level driving of a NeoPixel::
import esp
esp.neopixel_write(pin, grb_buf, is800khz)
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 , and start daemon using::
import webrepl
webrepl.start()
(Release version will have it started on boot by default.)
On a first connection, you will be prompted to set password for future
sessions to use.
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
routers is set up and works correctly, you may also use it while connecting
to your normal Internet access point (use ESP8266 AP connection method if
face any issues).
WebREPL is an experimental feature and a work in progress, and has known
issues. There's also provision to transfer (both upload and download)
files over WebREPL connection, but it has unstable status (be ready to
reboot a module in case of issues). It still may be a practical way to
get script files onto ESP8266, so give it a try using ``webrepl_cli.py``
from the repository above. See forum for other community-supported
alternatives to transfer files to ESP8266.