# SPDX-FileCopyrightText: 2016 Scott Shawcroft for Adafruit Industries
#
# SPDX-License-Identifier: MIT
# pylint: disable=too-few-public-methods
"""
`adafruit_bus_device.spi_device` - SPI Bus Device
====================================================
"""
import time
try:
from typing import Optional, Type
from types import TracebackType
# Used only for type annotations.
from busio import SPI
from digitalio import DigitalInOut
except ImportError:
pass
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"
[docs]
class SPIDevice:
"""
Represents a single SPI device and manages locking the bus and the device
address.
:param ~busio.SPI spi: The SPI bus the device is on
:param ~digitalio.DigitalInOut chip_select: The chip select pin object that implements the
DigitalInOut API.
:param bool cs_active_value: Set to True if your device requires CS to be active high.
Defaults to False.
:param int baudrate: The desired SCK clock rate in Hertz. The actual clock rate may be
higher or lower due to the granularity of available clock settings (MCU dependent).
:param int polarity: The base state of the SCK clock pin (0 or 1).
:param int phase: The edge of the clock that data is captured. First (0) or second (1).
Rising or falling depends on SCK clock polarity.
:param int extra_clocks: The minimum number of clock cycles to cycle the bus after CS is high.
(Used for SD cards.)
.. note:: This class is **NOT** built into CircuitPython. See
:ref:`here for install instructions <bus_device_installation>`.
Example:
.. code-block:: python
import busio
import digitalio
from board import *
from adafruit_bus_device.spi_device import SPIDevice
with busio.SPI(SCK, MOSI, MISO) as spi_bus:
cs = digitalio.DigitalInOut(D10)
device = SPIDevice(spi_bus, cs)
bytes_read = bytearray(4)
# The object assigned to spi in the with statements below
# is the original spi_bus object. We are using the busio.SPI
# operations busio.SPI.readinto() and busio.SPI.write().
with device as spi:
spi.readinto(bytes_read)
# A second transaction
with device as spi:
spi.write(bytes_read)
"""
def __init__(
self,
spi: SPI,
chip_select: Optional[DigitalInOut] = None,
*,
cs_active_value: bool = False,
baudrate: int = 100000,
polarity: int = 0,
phase: int = 0,
extra_clocks: int = 0
) -> None:
self.spi = spi
self.baudrate = baudrate
self.polarity = polarity
self.phase = phase
self.extra_clocks = extra_clocks
self.chip_select = chip_select
self.cs_active_value = cs_active_value
if self.chip_select:
self.chip_select.switch_to_output(value=not self.cs_active_value)
def __enter__(self) -> SPI:
while not self.spi.try_lock():
time.sleep(0)
self.spi.configure(
baudrate=self.baudrate, polarity=self.polarity, phase=self.phase
)
if self.chip_select:
self.chip_select.value = self.cs_active_value
return self.spi
def __exit__(
self,
exc_type: Optional[Type[type]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> bool:
if self.chip_select:
self.chip_select.value = not self.cs_active_value
if self.extra_clocks > 0:
buf = bytearray(1)
buf[0] = 0xFF
clocks = self.extra_clocks // 8
if self.extra_clocks % 8 != 0:
clocks += 1
for _ in range(clocks):
self.spi.write(buf)
self.spi.unlock()
return False