docs/rp2: Add skeleton docs for the rp2 port.

Author: pi-mst

docs/index.rst

@@ -11,5 +11,6 @@ MicroPython documentation and references
     pyboard/quickref.rst
     esp8266/quickref.rst
     esp32/quickref.rst
+    rp2/quickref.rst
     wipy/quickref.rst
     unix/quickref.rst

docs/rp2/general.rst

@@ -0,0 +1,18 @@
+.. _rp2_general:
+
+General information about the RP2xxx port
+=========================================
+
+The rp2 port supports boards powered by the Raspberry Pi Foundation's RP2xxx
+family of microcontrollers, most notably the Raspberry Pi Pico that employs
+the RP2040.
+
+Technical specifications and SoC datasheets
+-------------------------------------------
+
+Datasheets!
+
+Short summary of tech specs!
+
+Description of general structure of the port (it's built on top of the APIs
+provided by the Raspberry Pi SDK).

docs/rp2/img/rpipico.jpg

@@ -0,0 +1,288 @@
+.. _rp2_quickref:
+
+Quick reference for the RP2
+===========================
+
+.. image:: img/rpipico.jpg
+    :alt: Raspberry Pi Pico
+    :width: 640px
+
+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:
+
+.. toctree::
+   :maxdepth: 1
+
+   general.rst
+   tutorial/intro.rst
+
+Installing MicroPython
+----------------------
+
+See the corresponding section of tutorial: :ref:`rp2_intro`. 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.
+
+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:`rp2` module::
+
+    import rp2
+
+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
+------
+
+How do they work?
+
+.. _rp2_Pins_and_GPIO:
+
+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
+
+UART (serial bus)
+-----------------
+
+See :ref:`machine.UART <machine.UART>`. ::
+
+    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?
+
+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_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 :ref:`machine.ADC <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
+:ref:`machine.SoftSPI <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
+
+.. Warning::
+   Currently *all* of ``sck``, ``mosi`` and ``miso`` *must* be specified when
+   initialising Software SPI.
+
+Hardware SPI bus
+----------------
+
+Hardware SPI is accessed via the :ref:`machine.SPI <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 :ref:`machine.SoftI2C <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 :ref:`machine.I2C <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)
+---------------------
+
+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
+
+WDT (Watchdog timer)
+--------------------
+
+Is there a watchdog timer?
+
+See :ref:`machine.WDT <machine.WDT>`. ::
+
+    from machine import WDT
+
+    # enable the WDT with a timeout of 5s (1s is the minimum)
+    wdt = WDT(timeout=5000)
+    wdt.feed()
+
+Deep-sleep mode
+---------------
+
+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)
+
+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 and APA106 driver
+--------------------------
+
+Use the ``neopixel`` and ``apa106`` modules::
+
+    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
+
+
+The APA106 driver extends NeoPixel, but internally uses a different colour order::
+
+    from apa106 import APA106
+    ap = APA106(pin, 8)
+    r, g, b = ap[0]
+
+APA102 (DotStar) uses a different driver as it has an additional clock pin.

docs/rp2/quickref.rst

@@ -0,0 +1,6 @@
+.. _rp2_intro:
+
+Getting started with MicroPython on the RP2xxx
+==============================================
+
+Let's get started!

docs/rp2/tutorial/intro.rst

@@ -58,6 +58,10 @@ <h1>MicroPython documentation</h1>
         <a class="biglink" href="{{ pathto("esp32/quickref") }}">Quick reference for the ESP32</a><br/>
         <span class="linkdescr">pinout for ESP32-based boards, snippets of useful code, and a tutorial</span>
       </p>
+      <p class="biglink">
+        <a class="biglink" href="{{ pathto("rp2/quickref") }}">Quick reference for the Raspberry Pi RP2xxx</a><br/>
+        <span class="linkdescr">pinout for rp2xxx-based boards, snippets of useful code, and a tutorial</span>
+      </p>
       <p class="biglink">
         <a class="biglink" href="{{ pathto("wipy/quickref") }}">Quick reference for the WiPy/CC3200</a><br/>
         <span class="linkdescr">pinout for the WiPy/CC3200, snippets of useful code, and a tutorial</span>