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100 lines
3.9 KiB
100 lines
3.9 KiB
# The MIT License (MIT)
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#
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# Copyright (c) 2016 Scott Shawcroft for Adafruit Industries
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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# pylint: disable=too-few-public-methods
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"""
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`adafruit_bus_device.spi_device` - SPI Bus Device
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====================================================
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"""
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__version__ = "2.2.2"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"
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class SPIDevice:
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"""
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Represents a single SPI device and manages locking the bus and the device
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address.
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:param ~busio.SPI spi: The SPI bus the device is on
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:param ~digitalio.DigitalInOut chip_select: The chip select pin object that implements the
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DigitalInOut API.
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:param int extra_clocks: The minimum number of clock cycles to cycle the bus after CS is high.
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(Used for SD cards.)
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.. note:: This class is **NOT** built into CircuitPython. See
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:ref:`here for install instructions <bus_device_installation>`.
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Example:
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.. code-block:: python
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import busio
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import digitalio
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from board import *
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from adafruit_bus_device.spi_device import SPIDevice
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with busio.SPI(SCK, MOSI, MISO) as spi_bus:
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cs = digitalio.DigitalInOut(D10)
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device = SPIDevice(spi_bus, cs)
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bytes_read = bytearray(4)
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# The object assigned to spi in the with statements below
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# is the original spi_bus object. We are using the busio.SPI
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# operations busio.SPI.readinto() and busio.SPI.write().
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with device as spi:
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spi.readinto(bytes_read)
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# A second transaction
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with device as spi:
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spi.write(bytes_read)
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"""
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def __init__(self, spi, chip_select=None, *,
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baudrate=100000, polarity=0, phase=0, extra_clocks=0):
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self.spi = spi
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self.baudrate = baudrate
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self.polarity = polarity
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self.phase = phase
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self.extra_clocks = extra_clocks
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self.chip_select = chip_select
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if self.chip_select:
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self.chip_select.switch_to_output(value=True)
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def __enter__(self):
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while not self.spi.try_lock():
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pass
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self.spi.configure(baudrate=self.baudrate, polarity=self.polarity,
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phase=self.phase)
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if self.chip_select:
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self.chip_select.value = False
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return self.spi
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def __exit__(self, *exc):
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if self.chip_select:
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self.chip_select.value = True
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if self.extra_clocks > 0:
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buf = bytearray(1)
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buf[0] = 0xff
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clocks = self.extra_clocks // 8
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if self.extra_clocks % 8 != 0:
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clocks += 1
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for _ in range(clocks):
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self.spi.write(buf)
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self.spi.unlock()
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return False
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