479 lines
16 KiB
ReStructuredText
479 lines
16 KiB
ReStructuredText
.. _esp32_quickref:
|
|
|
|
Quick reference for the ESP32
|
|
=============================
|
|
|
|
.. image:: img/esp32.jpg
|
|
:alt: ESP32 board
|
|
:width: 640px
|
|
|
|
The Espressif ESP32 Development Board (image attribution: Adafruit).
|
|
|
|
Below is a quick reference for ESP32-based boards. If it is your first time
|
|
working with this board it may be useful to get an overview of the microcontroller:
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
general.rst
|
|
tutorial/intro.rst
|
|
|
|
Installing MicroPython
|
|
----------------------
|
|
|
|
See the corresponding section of tutorial: :ref:`esp32_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(240000000) # set the CPU frequency to 240 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)
|
|
|
|
# low level methods to interact with flash storage
|
|
esp.flash_size()
|
|
esp.flash_user_start()
|
|
esp.flash_erase(sector_no)
|
|
esp.flash_write(byte_offset, buffer)
|
|
esp.flash_read(byte_offset, buffer)
|
|
|
|
The :mod:`esp32` module::
|
|
|
|
import esp32
|
|
|
|
esp32.hall_sensor() # read the internal hall sensor
|
|
esp32.raw_temperature() # read the internal temperature of the MCU, in Farenheit
|
|
esp32.ULP() # access to the Ultra-Low-Power Co-processor
|
|
|
|
Note that the temperature sensor in the ESP32 will typically read higher than
|
|
ambient due to the IC getting warm while it runs. This effect can be minimised
|
|
by reading the temperature sensor immediately after waking up from sleep.
|
|
|
|
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('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.config(essid='ESP-AP') # set the ESSID of the access point
|
|
ap.active(True) # activate the interface
|
|
|
|
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 :mod:`socket <usocket>` module can be used
|
|
to create and use TCP/UDP sockets as usual, and the ``urequests`` module for
|
|
convenient HTTP requests.
|
|
|
|
Delay and timing
|
|
----------------
|
|
|
|
Use the :mod:`time <utime>` 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 from the following ranges (inclusive): 0-19, 21-23, 25-27, 32-39.
|
|
These correspond to the actual GPIO pin numbers of ESP32 chip. Note that many
|
|
end-user boards use their own adhoc pin numbering (marked e.g. D0, D1, ...).
|
|
For mapping between board logical pins and physical chip pins consult your board
|
|
documentation.
|
|
|
|
Notes:
|
|
|
|
* Pins 1 and 3 are REPL UART TX and RX respectively
|
|
|
|
* Pins 6, 7, 8, 11, 16, and 17 are used for connecting the embedded flash,
|
|
and are not recommended for other uses
|
|
|
|
* Pins 34-39 are input only, and also do not have internal pull-up resistors
|
|
|
|
PWM (pulse width modulation)
|
|
----------------------------
|
|
|
|
PWM can be enabled on all output-enabled pins. The base frequency can
|
|
range from 1Hz to 40MHz but there is a tradeoff; as the base frequency
|
|
*increases* the duty resolution *decreases*. See
|
|
`LED Control <https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/ledc.html>`_
|
|
for more details.
|
|
|
|
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=20000, duty=512) # create and configure in one go
|
|
|
|
ADC (analog to digital conversion)
|
|
----------------------------------
|
|
|
|
On the ESP32 ADC functionality is available on Pins 32-39. Note that, when
|
|
using the default configuration, input voltages on the ADC pin must be between
|
|
0.0v and 1.0v (anything above 1.0v will just read as 4095). Attenuation must
|
|
be applied in order to increase this usable voltage range.
|
|
|
|
Use the :ref:`machine.ADC <machine.ADC>` class::
|
|
|
|
from machine import ADC
|
|
|
|
adc = ADC(Pin(32)) # create ADC object on ADC pin
|
|
adc.read() # read value, 0-4095 across voltage range 0.0v - 1.0v
|
|
|
|
adc.atten(ADC.ATTN_11DB) # set 11dB input attentuation (voltage range roughly 0.0v - 3.6v)
|
|
adc.width(ADC.WIDTH_9BIT) # set 9 bit return values (returned range 0-511)
|
|
adc.read() # read value using the newly configured attenuation and width
|
|
|
|
ESP32 specific ADC class method reference:
|
|
|
|
.. method:: ADC.atten(attenuation)
|
|
|
|
This method allows for the setting of the amount of attenuation on the
|
|
input of the ADC. This allows for a wider possible input voltage range,
|
|
at the cost of accuracy (the same number of bits now represents a wider
|
|
range). The possible attenuation options are:
|
|
|
|
- ``ADC.ATTN_0DB``: 0dB attenuation, gives a maximum input voltage
|
|
of 1.00v - this is the default configuration
|
|
- ``ADC.ATTN_2_5DB``: 2.5dB attenuation, gives a maximum input voltage
|
|
of approximately 1.34v
|
|
- ``ADC.ATTN_6DB``: 6dB attenuation, gives a maximum input voltage
|
|
of approximately 2.00v
|
|
- ``ADC.ATTN_11DB``: 11dB attenuation, gives a maximum input voltage
|
|
of approximately 3.6v
|
|
|
|
.. Warning::
|
|
Despite 11dB attenuation allowing for up to a 3.6v range, note that the
|
|
absolute maximum voltage rating for the input pins is 3.6v, and so going
|
|
near this boundary may be damaging to the IC!
|
|
|
|
.. method:: ADC.width(width)
|
|
|
|
This method allows for the setting of the number of bits to be utilised
|
|
and returned during ADC reads. Possible width options are:
|
|
|
|
- ``ADC.WIDTH_9BIT``: 9 bit data
|
|
- ``ADC.WIDTH_10BIT``: 10 bit data
|
|
- ``ADC.WIDTH_11BIT``: 11 bit data
|
|
- ``ADC.WIDTH_12BIT``: 12 bit data - this is the default configuration
|
|
|
|
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.SPI <machine.SPI>`
|
|
class::
|
|
|
|
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
|
|
|
|
.. Warning::
|
|
Currently *all* of ``sck``, ``mosi`` and ``miso`` *must* be specified when
|
|
initialising Software SPI.
|
|
|
|
Hardware SPI bus
|
|
----------------
|
|
|
|
There are two hardware SPI channels that allow faster (up to 80Mhz)
|
|
transmission rates, but are only supported on a subset of pins.
|
|
|
|
===== =========== ============
|
|
\ HSPI (id=1) VSPI (id=2)
|
|
===== =========== ============
|
|
sck 14 18
|
|
mosi 13 23
|
|
miso 12 19
|
|
===== =========== ============
|
|
|
|
Hardware SPI has the same methods as Software SPI above::
|
|
|
|
from machine import Pin, SPI
|
|
|
|
hspi = SPI(1, 10000000, sck=Pin(14), mosi=Pin(13), miso=Pin(12))
|
|
vspi = SPI(2, baudrate=80000000, polarity=0, phase=0, bits=8, firstbit=0, sck=Pin(18), mosi=Pin(23), miso=Pin(19))
|
|
|
|
|
|
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::
|
|
|
|
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
|
|
|
|
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
|
|
|
|
Deep-sleep mode
|
|
---------------
|
|
|
|
The following code can be used to sleep, wake and check the reset cause::
|
|
|
|
import machine
|
|
|
|
# check if the device woke from a deep sleep
|
|
if machine.reset_cause() == machine.DEEPSLEEP_RESET:
|
|
print('woke from a deep sleep')
|
|
|
|
# put the device to sleep for 10 seconds
|
|
machine.deepsleep(10000)
|
|
|
|
Notes:
|
|
|
|
* Calling ``deepsleep()`` without an argument will put the device to sleep
|
|
indefinitely
|
|
* A software reset does not change the reset cause
|
|
|
|
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
|
|
|
|
For low-level driving of a NeoPixel::
|
|
|
|
import esp
|
|
esp.neopixel_write(pin, grb_buf, is800khz)
|
|
|
|
.. 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.
|
|
|
|
|
|
Capacitive Touch
|
|
----------------
|
|
|
|
Use the ``TouchPad`` class in the ``machine`` module::
|
|
|
|
from machine import TouchPad, Pin
|
|
|
|
t = TouchPad(Pin(14))
|
|
t.read() # Returns a smaller number when touched
|
|
|
|
``TouchPad.read`` returns a value relative to the capacitive variation. Small numbers (typically in
|
|
the *tens*) are common when a pin is touched, larger numbers (above *one thousand*) when
|
|
no touch is present. However the values are *relative* and can vary depending on the board
|
|
and surrounding composition so some calibration may be required.
|
|
|
|
There are ten capacitive touch-enabled pins that can be used on the ESP32: 0, 2, 4, 12, 13
|
|
14, 15, 27, 32, 33. Trying to assign to any other pins will result in a ``ValueError``.
|
|
|
|
Note that TouchPads can be used to wake an ESP32 from sleep::
|
|
|
|
import machine
|
|
from machine import TouchPad, Pin
|
|
import esp32
|
|
|
|
t = TouchPad(Pin(14))
|
|
t.config(500) # configure the threshold at which the pin is considered touched
|
|
esp32.wake_on_touch(True)
|
|
machine.lightsleep() # put the MCU to sleep until a touchpad is touched
|
|
|
|
For more details on touchpads refer to `Espressif Touch Sensor
|
|
<https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/touch_pad.html>`_.
|
|
|
|
|
|
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)
|
|
|
|
WebREPL (web browser interactive prompt)
|
|
----------------------------------------
|
|
|
|
WebREPL (REPL over WebSockets, accessible via a web browser) is an
|
|
experimental feature available in ESP32 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()
|
|
|
|
# or, start with a specific password
|
|
webrepl.start(password='mypass')
|
|
|
|
The WebREPL daemon listens on all active interfaces, which can be STA or
|
|
AP. This allows you to connect to the ESP32 via a router (the STA
|
|
interface) or directly when connected to its access point.
|
|
|
|
In addition to terminal/command prompt access, WebREPL also has provision
|
|
for file transfer (both upload and download). The web client has buttons for
|
|
the corresponding functions, or you can use the command-line client
|
|
``webrepl_cli.py`` from the repository above.
|
|
|
|
See the MicroPython forum for other community-supported alternatives
|
|
to transfer files to an ESP32 board.
|