Quick reference for the RP2¶
The Raspberry Pi Pico Development Board (image attribution: Raspberry Pi Foundation).
Below is a quick reference for Raspberry Pi RP2xxx boards. If it is your first time working with this board it may be useful to get an overview of the microcontroller:
See the corresponding section of tutorial: Getting started with MicroPython on the RP2xxx. It also includes a troubleshooting subsection.
General board control¶
The MicroPython REPL is on the USB serial port. 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(240000000) # set the CPU frequency to 240 MHz
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(time.ticks_ms(), start) # compute time difference
How do they work?
Pins and GPIO¶
Use the 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
UART (serial bus)¶
from machine import UART uart1 = UART(1, baudrate=9600, tx=33, rx=32) uart1.write('hello') # write 5 bytes uart1.read(5) # read up to 5 bytes
PWM (pulse width modulation)¶
How does PWM work on the RPi RP2xxx?
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_u16() # get current duty cycle, range 0-65535 pwm0.duty_u16(200) # set duty cycle, range 0-65535 pwm0.deinit() # turn off PWM on the pin
ADC (analog to digital conversion)¶
How does the ADC module work?
Use the machine.ADC class:
from machine import ADC adc = ADC(Pin(32)) # create ADC object on ADC pin adc.read_u16() # read value, 0-65535 across voltage range 0.0v - 3.3v
Software SPI bus¶
Software SPI (using bit-banging) works on all pins, and is accessed via the machine.SoftSPI class:
from machine import Pin, SoftSPI # construct a SoftSPI 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
Currently all of
miso must be specified when
initialising Software SPI.
Hardware SPI bus¶
Hardware SPI is accessed via the machine.SPI class and has the same methods as software SPI above:
from machine import Pin, SPI spi = SPI(1, 10000000) spi = SPI(1, 10000000, sck=Pin(14), mosi=Pin(13), miso=Pin(12)) spi = SPI(2, baudrate=80000000, polarity=0, phase=0, bits=8, firstbit=0, sck=Pin(18), mosi=Pin(23), miso=Pin(19))
Software I2C bus¶
Software I2C (using bit-banging) works on all output-capable pins, and is accessed via the machine.SoftI2C class:
from machine import Pin, SoftI2C i2c = SoftI2C(scl=Pin(5), sda=Pin(4), freq=100000) i2c.scan() # scan for devices i2c.readfrom(0x3a, 4) # read 4 bytes from device with address 0x3a i2c.writeto(0x3a, '12') # write '12' to device with address 0x3a buf = bytearray(10) # create a buffer with 10 bytes i2c.writeto(0x3a, buf) # write the given buffer to the slave
Hardware I2C bus¶
The driver is accessed via the machine.I2C class and has the same methods as software I2C above:
from machine import Pin, I2C i2c = I2C(0) i2c = I2C(1, scl=Pin(5), sda=Pin(4), freq=400000)
Real time clock (RTC)¶
from machine import RTC rtc = RTC() rtc.datetime((2017, 8, 23, 2, 12, 48, 0, 0)) # set a specific date and time rtc.datetime() # get date and time
WDT (Watchdog timer)¶
Is there a watchdog timer?
from machine import WDT # enable the WDT with a timeout of 5s (1s is the minimum) wdt = WDT(timeout=5000) wdt.feed()
Is there deep-sleep support for the rp2?
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)
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
convert_temp() method must be called each time you want to
sample the temperature.
NeoPixel and APA106 driver¶
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
The APA106 driver extends NeoPixel, but internally uses a different colour order:
from apa106 import APA106 ap = APA106(pin, 8) r, g, b = ap
APA102 (DotStar) uses a different driver as it has an additional clock pin.