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docs/library: Add initial API reference for rp2 module and its classes.

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All the method signatures from rp2_pio.c and friends have been taken and
converted to RST format, then explanatory notes added for each signature.

Signed-off-by: Tim Radvan <tim@tjvr.org>
This commit is contained in:
Tim Radvan 2021-04-16 12:18:04 +01:00 committed by Damien George
parent 9eea51b730
commit fd24e649fd
6 changed files with 359 additions and 2 deletions
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11
docs/library/index.rst
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@ -165,3 +165,14 @@ The following libraries are specific to the ESP8266 and ESP32.
esp.rst esp.rst
esp32.rst esp32.rst
Libraries specific to the RP2040
--------------------------------
The following libraries are specific to the RP2040, as used in the Raspberry Pi Pico.
.. toctree::
:maxdepth: 2
rp2.rst

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docs/library/machine.rst
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@ -64,9 +64,11 @@ Interrupt related functions
Power related functions Power related functions
----------------------- -----------------------
.. function:: freq() .. function:: freq([hz])
Returns CPU frequency in hertz. Returns the CPU frequency in hertz.
On some ports this can also be used to set the CPU frequency by passing in *hz*.
.. function:: idle() .. function:: idle()

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docs/library/rp2.Flash.rst Normal file
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.. currentmodule:: rp2
.. _rp2.Flash:
class Flash -- access to built-in flash storage
===============================================
This class gives access to the SPI flash memory.
In most cases, to store persistent data on the device, you'll want to use a
higher-level abstraction, for example the filesystem via Python's standard file
API, but this interface is useful to :ref:`customise the filesystem
configuration <filesystem>` or implement a low-level storage system for your
application.
Constructors
------------
.. class:: Flash()
Gets the singleton object for accessing the SPI flash memory.
Methods
-------
.. method:: Flash.readblocks(block_num, buf)
Flash.readblocks(block_num, buf, offset)
.. method:: Flash.writeblocks(block_num, buf)
Flash.writeblocks(block_num, buf, offset)
.. method:: Flash.ioctl(cmd, arg)
These methods implement the simple and extended
:ref:`block protocol <block-device-interface>` defined by
:class:`uos.AbstractBlockDev`.

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docs/library/rp2.PIO.rst Normal file
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.. currentmodule:: rp2
.. _rp2.PIO:
class PIO -- advanced PIO usage
===============================
The :class:`PIO` class gives access to an instance of the RP2040's PIO
(programmable I/O) interface.
The preferred way to interact with PIO is using :class:`rp2.StateMachine`, the
PIO class is for advanced use.
For assembling PIO programs, see :func:`rp2.asm_pio`.
Constructors
------------
.. class:: PIO(id)
Gets the PIO instance numbered *id*. The RP2040 has two PIO instances,
numbered 0 and 1.
Raises a ``ValueError`` if any other argument is provided.
Methods
-------
.. method:: PIO.add_program(program)
Add the *program* to the instruction memory of this PIO instance.
The amount of memory available for programs on each PIO instance is
limited. If there isn't enough space left in the PIO's program memory
this method will raise ``OSError(ENOMEM)``.
.. method:: PIO.remove_program([program])
Remove *program* from the instruction memory of this PIO instance.
If no program is provided, it removes all programs.
It is not an error to remove a program which has already been removed.
.. method:: PIO.state_machine(id, [program, ...])
Gets the state machine numbered *id*. On the RP2040, each PIO instance has
four state machines, numbered 0 to 3.
Optionally initialize it with a *program*: see `StateMachine.init`.
>>> rp2.PIO(1).state_machine(3)
StateMachine(7)
.. method:: PIO.irq(handler=None, trigger=IRQ_SM0|IRQ_SM1|IRQ_SM2|IRQ_SM3, hard=False)
Returns the IRQ object for this PIO instance.
MicroPython only uses IRQ 0 on each PIO instance. IRQ 1 is not available.
Optionally configure it.
Constants
---------
.. data:: PIO.IN_LOW
PIO.IN_HIGH
PIO.OUT_LOW
PIO.OUT_HIGH
These constants are used for the *out_init*, *set_init*, and *sideset_init*
arguments to `asm_pio`.
.. data:: PIO.SHIFT_LEFT
PIO.SHIFT_RIGHT
These constants are used for the *in_shiftdir* and *out_shiftdir* arguments
to `asm_pio` or `StateMachine.init`.
.. data:: PIO.JOIN_NONE
PIO.JOIN_TX
PIO.JOIN_RX
These constants are used for the *fifo_join* argument to `asm_pio`.
.. data:: PIO.IRQ_SM0
PIO.IRQ_SM1
PIO.IRQ_SM2
PIO.IRQ_SM3
These constants are used for the *trigger* argument to `PIO.irq`.

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docs/library/rp2.StateMachine.rst Normal file
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.. currentmodule:: rp2
.. _rp2.StateMachine:
class StateMachine -- access to the RP2040's programmable I/O interface
=======================================================================
The :class:`StateMachine` class gives access to the RP2040's PIO (programmable
I/O) interface.
For assembling PIO programs, see :func:`rp2.asm_pio`.
Constructors
------------
.. class:: StateMachine(id, [program, ...])
Get the state machine numbered *id*. The RP2040 has two identical PIO
instances, each with 4 state machines: so there are 8 state machines in
total, numbered 0 to 7.
Optionally initialize it with the given program *program*: see
`StateMachine.init`.
Methods
-------
.. method:: StateMachine.init(program, freq=-1, *, in_base=None, out_base=None, set_base=None, jmp_pin=None, sideset_base=None, in_shiftdir=None, out_shiftdir=None, push_thresh=None, pull_thresh=None)
Configure the state machine instance to run the given *program*.
The program is added to the instruction memory of this PIO instance. If the
instruction memory already contains this program, then its offset is
re-used so as to save on instruction memory.
- *freq* is the frequency in Hz to run the state machine at. Defaults to
the system clock frequency.
The clock divider is computed as ``system clock frequency / freq``, so
there can be slight rounding errors.
The minimum possible clock divider is one 65536th of the system clock: so
at the default system clock frequency of 125MHz, the minimum value of
*freq* is ``1908``. To run state machines at slower frequencies, you'll
need to reduce the system clock speed with `machine.freq()`.
- *in_base* is the first pin to use for ``in()`` instructions.
- *out_base* is the first pin to use for ``out()`` instructions.
- *set_base* is the first pin to use for ``set()`` instructions.
- *jmp_pin* is the first pin to use for ``jmp(pin, ...)`` instructions.
- *sideset_base* is the first pin to use for side-setting.
- *in_shiftdir* is the direction the ISR will shift, either
`PIO.SHIFT_LEFT` or `PIO.SHIFT_RIGHT`.
- *out_shiftdir* is the direction the OSR will shift, either
`PIO.SHIFT_LEFT` or `PIO.SHIFT_RIGHT`.
- *push_thresh* is the threshold in bits before auto-push or conditional
re-pushing is triggered.
- *pull_thresh* is the threshold in bits before auto-push or conditional
re-pushing is triggered.
.. method:: StateMachine.active([value])
Gets or sets whether the state machine is currently running.
>>> sm.active()
True
>>> sm.active(0)
False
.. method:: StateMachine.restart()
Restarts the state machine and jumps to the beginning of the program.
This method clears the state machine's internal state using the RP2040's
``SM_RESTART`` register. This includes:
- input and output shift counters
- the contents of the input shift register
- the delay counter
- the waiting-on-IRQ state
- a stalled instruction run using `StateMachine.exec()`
.. method:: StateMachine.exec(instr)
Execute a single PIO instruction. Uses `asm_pio_encode` to encode the
instruction from the given string *instr*.
>>> sm.exec("set(0, 1)")
.. method:: StateMachine.get(buf=None, shift=0)
Pull a word from the state machine's RX FIFO.
If the FIFO is empty, it blocks until data arrives (i.e. the state machine
pushes a word).
The value is shifted right by *shift* bits before returning, i.e. the
return value is ``word >> shift``.
.. method:: StateMachine.put(value, shift=0)
Push a word onto the state machine's TX FIFO.
If the FIFO is full, it blocks until there is space (i.e. the state machine
pulls a word).
The value is first shifted left by *shift* bits, i.e. the state machine
receives ``value << shift``.
.. method:: StateMachine.rx_fifo()
Returns the number of words in the state machine's RX FIFO. A value of 0
indicates the FIFO is empty.
Useful for checking if data is waiting to be read, before calling
`StateMachine.get()`.
.. method:: StateMachine.tx_fifo()
Returns the number of words in the state machine's TX FIFO. A value of 0
indicates the FIFO is empty.
Useful for checking if there is space to push another word using
`StateMachine.put()`.
.. method:: StateMachine.irq(handler=None, trigger=0|1, hard=False)
Returns the IRQ object for the given StateMachine.
Optionally configure it.

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.. currentmodule:: rp2
:mod:`rp2` --- functionality specific to the RP2040
===================================================
.. module:: rp2
:synopsis: functionality specific to the RP2
The ``rp2`` module contains functions and classes specific to the RP2040, as
used in the Raspberry Pi Pico.
See the `RP2040 Python datasheet
<https://datasheets.raspberrypi.org/pico/raspberry-pi-pico-python-sdk.pdf>`_
for more information, and `pico-micropython-examples
<https://github.com/raspberrypi/pico-micropython-examples/tree/master/pio>`_
for example code.
PIO related functions
---------------------
The ``rp2`` module includes functions for assembling PIO programs.
For running PIO programs, see :class:`rp2.StateMachine`.
.. function:: asm_pio(*, out_init=None, set_init=None, sideset_init=None, in_shiftdir=0, out_shiftdir=0, autopush=False, autopull=False, push_thresh=32, pull_thresh=32, fifo_join=PIO.JOIN_NONE)
Assemble a PIO program.
The following parameters control the initial state of the GPIO pins, as one
of `PIO.IN_LOW`, `PIO.IN_HIGH`, `PIO.OUT_LOW` or `PIO.OUT_HIGH`. If the
program uses more than one pin, provide a tuple, e.g.
``out_init=(PIO.OUT_LOW, PIO.OUT_LOW)``.
- *out_init* configures the pins used for ``out()`` instructions.
- *set_init* configures the pins used for ``set()`` instructions. There can
be at most 5.
- *sideset_init* configures the pins used side-setting. There can be at
most 5.
The following parameters are used by default, but can be overriden in
`StateMachine.init()`:
- *in_shiftdir* is the default direction the ISR will shift, either
`PIO.SHIFT_LEFT` or `PIO.SHIFT_RIGHT`.
- *out_shiftdir* is the default direction the OSR will shift, either
`PIO.SHIFT_LEFT` or `PIO.SHIFT_RIGHT`.
- *push_thresh* is the threshold in bits before auto-push or conditional
re-pushing is triggered.
- *pull_thresh* is the threshold in bits before auto-push or conditional
re-pushing is triggered.
The remaining parameters are:
- *autopush* configures whether auto-push is enabled.
- *autopull* configures whether auto-pull is enabled.
- *fifo_join* configures whether the 4-word TX and RX FIFOs should be
combined into a single 8-word FIFO for one direction only. The options
are `PIO.JOIN_NONE`, `PIO.JOIN_RX` and `PIO.JOIN_TX`.
.. function:: asm_pio_encode(instr, sideset_count)
Assemble a single PIO instruction. You usually want to use `asm_pio()`
instead.
>>> rp2.asm_pio_encode("set(0, 1)", 0)
57345
.. class:: PIOASMError
This exception is raised from `asm_pio()` or `asm_pio_encode()` if there is
an error assembling a PIO program.
Classes
-------
.. toctree::
:maxdepth: 1
rp2.Flash.rst
rp2.PIO.rst
rp2.StateMachine.rst