RP2 快速参考 ¶
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:
安装 MicroPython ¶
见教程相应章节： 在 RP2xxx 上快速入门 MicroPython . It also includes a troubleshooting subsection.
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
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))
引脚和 GPIO ¶
使用 machine.Pin 类：
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 (串行总线) ¶
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.
见 machine.UART .
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 在 RP2xxx 上快速入门 MicroPython for details on how to enable REPL over UART.
PWM (脉冲宽度调制) ¶
There are 8 independent channels each of which have 2 outputs making it 16 PWM channels in total which can be clocked from 7Hz to 125Mhz.
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 (模拟到数字转换) ¶
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.
使用 machine.ADC 类：
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
软件 SPI 总线 ¶
Software SPI (using bit-banging) works on all pins, and is accessed via the machine.SoftSPI 类：
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
指定当初始化软件 SPI 时。
硬件 SPI 总线 ¶
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))
软件 I2C 总线 ¶
Software I2C (using bit-banging) works on all output-capable pins, and is accessed via the machine.SoftI2C 类：
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
硬件 I2C 总线 ¶
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)
RTC (实时时钟) ¶
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 (看门狗计时器) ¶
The RP2040 has a watchdog which is a countdown timer that can restart parts of the chip if it reaches zero.
见 machine.WDT .
from machine import WDT # enable the WDT with a timeout of 5s (1s is the minimum) wdt = WDT(timeout=5000) wdt.feed()
OneWire 驱动程序 ¶
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
method must be called each time you want to sample the temperature.
NeoPixel 和 APA106 驱动程序 ¶
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.