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 accessed via 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
RP2040’s system timer peripheral provides a global microsecond timebase and generates interrupts for it. The software timer is available currently, and there are unlimited number of them (memory permitting). There is no need to specify the timer id (id=-1 is supported at the moment) as it will default to this.
from machine import Timer tim = Timer(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(1)) tim.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(2))
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
Programmable IO (PIO)¶
PIO is useful to build low-level IO interfaces from scratch. See the
for detailed explanation of the assembly instructions.
Example using PIO to blink an LED at 1Hz:
from machine import Pin import rp2 @rp2.asm_pio(set_init=rp2.PIO.OUT_LOW) def blink_1hz(): # Cycles: 1 + 7 + 32 * (30 + 1) = 1000 set(pins, 1) set(x, 31)  label("delay_high") nop()  jmp(x_dec, "delay_high") # Cycles: 1 + 7 + 32 * (30 + 1) = 1000 set(pins, 0) set(x, 31)  label("delay_low") nop()  jmp(x_dec, "delay_low") # Create and start a StateMachine with blink_1hz, outputting on Pin(25) sm = rp2.StateMachine(0, blink_1hz, freq=2000, set_base=Pin(25)) sm.active(1)
UART (serial bus)¶
There are two UARTs, UART0 and UART1. UART0 can be mapped to GPIO 0/1, 12/13 and 16/17, and UART1 to GPIO 4/5 and 8/9.
from machine import UART, Pin uart1 = UART(1, baudrate=9600, tx=Pin(4), rx=Pin(5)) uart1.write('hello') # write 5 bytes uart1.read(5) # read up to 5 bytes
REPL over UART is disabled by default. You can see the Getting started with MicroPython on the RP2xxx for details on how to enable REPL over UART.
PWM (pulse width modulation)¶
There are 8 independent PWM generators called slices, which each have two channels making it 16 PWM channels in total which can be clocked from 8Hz to 62.5Mhz at a machine.freq() of 125Mhz. The two channels of a slice run at the same frequency, but can have a different duty rate. The two channels are usually assigned to adjacent GPIO pin pairs with even/odd numbers. So GPIO0 and GPIO1 are at slice 0, GPIO2 and GPIO3 are at slice 1, and so on. A certain channel can be assigned to different GPIO pins (see Pinout). For instance slice 0, channel A can be assigned to both GPIO0 and GPIO16.
from machine import Pin, PWM # create PWM object from a pin and set the frequency of slice 0 # and duty cycle for channel A pwm0 = PWM(Pin(0), freq=2000, duty_u16=32768) pwm0.freq() # get the current frequency of slice 0 pwm0.freq(1000) # set/change the frequency of slice 0 pwm0.duty_u16() # get the current duty cycle of channel A, range 0-65535 pwm0.duty_u16(200) # set the duty cycle of channel A, range 0-65535 pwm0.duty_u16(0) # stop the output at channel A print(pwm0) # show the properties of the PWM object. pwm0.deinit() # turn off PWM of slice 0, stopping channels A and B
ADC (analog to digital conversion)¶
RP2040 has five ADC channels in total, four of which are 12-bit SAR based ADCs: GP26, GP27, GP28 and GP29. The input signal for ADC0, ADC1, ADC2 and ADC3 can be connected with GP26, GP27, GP28, GP29 respectively (On Pico board, GP29 is connected to VSYS). The standard ADC range is 0-3.3V. The fifth channel is connected to the in-built temperature sensor and can be used for measuring the temperature.
Use the machine.ADC class:
from machine import ADC, Pin adc = ADC(Pin(26)) # 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=100_000, 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¶
The RP2040 has 2 hardware SPI buses which is accessed via the machine.SPI class and has the same methods as software SPI above:
from machine import Pin, SPI spi = SPI(1, 10_000_000) # Default assignment: sck=Pin(10), mosi=Pin(11), miso=Pin(8) spi = SPI(1, 10_000_000, sck=Pin(14), mosi=Pin(15), miso=Pin(12)) spi = SPI(0, baudrate=80_000_000, polarity=0, phase=0, bits=8, sck=Pin(6), mosi=Pin(7), miso=Pin(4))
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=100_000) 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 peripheral
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) # default assignment: scl=Pin(9), sda=Pin(8) i2c = I2C(1, scl=Pin(3), sda=Pin(2), freq=400_000)
from machine import I2S, Pin i2s = I2S(0, sck=Pin(16), ws=Pin(17), sd=Pin(18), mode=I2S.TX, bits=16, format=I2S.STEREO, rate=44100, ibuf=40000) # create I2S object i2s.write(buf) # write buffer of audio samples to I2S device i2s = I2S(1, sck=Pin(0), ws=Pin(1), sd=Pin(2), mode=I2S.RX, bits=16, format=I2S.MONO, rate=22050, ibuf=40000) # create I2S object i2s.readinto(buf) # fill buffer with audio samples from I2S device
ws pin number must be one greater than the
sck pin number.
The I2S class is currently available as a Technical Preview. During the preview period, feedback from users is encouraged. Based on this feedback, the I2S class API and implementation may be changed.
Two I2S buses are supported with id=0 and id=1.
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, eg. 2017/8/23 1:12:48 rtc.datetime() # get date and time
WDT (Watchdog timer)¶
The RP2040 has a watchdog which is a countdown timer that can restart parts of the chip if it reaches zero.
from machine import WDT # enable the WDT with a timeout of 5s (1s is the minimum) wdt = WDT(timeout=5000) wdt.feed()
The maximum value for timeout is 8388 ms.
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.