Quick reference for the ESP8266¶
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.
import machine machine.freq() # get the current frequency of the CPU machine.freq(160000000) # set the CPU frequency to 160 MHz
import esp esp.osdebug(None) # turn off vendor O/S debugging messages esp.osdebug(0) # redirect vendor O/S debugging messages to UART(0)
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¶
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
Virtual (RTOS-based) timers are supported. Use the
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¶
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
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.
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.
from machine import ADC adc = ADC(0) # create ADC object on ADC pin adc.read() # read value, 0-1024
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
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 i2c.readfrom(0x3a, 4, stop=False) # don't send a stop bit after reading i2c.writeto(0x3a, buf, stop=False) # don't send a stop bit after writing
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()
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
convert_temp() method must be called each time you want to
sample the temperature.
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 = (255, 255, 255) # set the first pixel to white np.write() # write data to all pixels r, g, b = np # 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
from the repository above. See forum for other community-supported
alternatives to transfer files to ESP8266.