|
|
- # The MIT License (MIT)
- #
- # Copyright (c) 2016 Scott Shawcroft for Adafruit Industries
- #
- # Permission is hereby granted, free of charge, to any person obtaining a copy
- # of this software and associated documentation files (the "Software"), to deal
- # in the Software without restriction, including without limitation the rights
- # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- # copies of the Software, and to permit persons to whom the Software is
- # furnished to do so, subject to the following conditions:
- #
- # The above copyright notice and this permission notice shall be included in
- # all copies or substantial portions of the Software.
- #
- # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- # THE SOFTWARE.
- # pylint: disable=too-few-public-methods
-
- """
- `adafruit_bus_device.spi_device` - SPI Bus Device
- ====================================================
- """
-
- __version__ = "2.2.2"
- __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"
-
- 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 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, chip_select=None, *,
- baudrate=100000, polarity=0, phase=0, extra_clocks=0):
- self.spi = spi
- self.baudrate = baudrate
- self.polarity = polarity
- self.phase = phase
- self.extra_clocks = extra_clocks
- self.chip_select = chip_select
- if self.chip_select:
- self.chip_select.switch_to_output(value=True)
-
- def __enter__(self):
- while not self.spi.try_lock():
- pass
- self.spi.configure(baudrate=self.baudrate, polarity=self.polarity,
- phase=self.phase)
- if self.chip_select:
- self.chip_select.value = False
- return self.spi
-
- def __exit__(self, *exc):
- if self.chip_select:
- self.chip_select.value = True
- 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
|