src/adafruit_blinka/microcontroller/ftdi_mpsse/mpsse/spi.py

   1 # SPDX-FileCopyrightText: 2021 Melissa LeBlanc-Williams for Adafruit Industries
   2 #
   3 # SPDX-License-Identifier: MIT
   4 """SPI Class for FTDI MPSSE"""
   5 from adafruit_blinka.microcontroller.ftdi_mpsse.mpsse.pin import Pin
   6 from adafruit_blinka.microcontroller.ftdi_mpsse.mpsse.url import (
   7     get_ft232h_url,
   8     get_ftx232h_url,
   9 )
  10
  11
  12 # pylint: disable=protected-access
  13 class SPI:
  14     """Custom SPI Class for FTDI MPSSE"""
  15
  16     MSB = 0
  17
  18     def __init__(self, spi_id=None):
  19         # pylint: disable=import-outside-toplevel
  20         from pyftdi.spi import SpiController
  21
  22         # pylint: enable=import-outside-toplevel
  23
  24         self._spi = SpiController(cs_count=1)
  25         if spi_id is None:
  26             self._spi.configure(get_ft232h_url())
  27         else:
  28             self._spi.configure(get_ftx232h_url(spi_id + 1))
  29         self._port = self._spi.get_port(0)
  30         self._port.set_frequency(100000)
  31         self._port._cpol = 0
  32         self._port._cpha = 0
  33         # Change GPIO controller to SPI
  34         Pin.mpsse_gpio = self._spi.get_gpio()
  35
  36     # pylint: disable=too-many-arguments,unused-argument
  37     def init(
  38         self,
  39         baudrate=100000,
  40         polarity=0,
  41         phase=0,
  42         bits=8,
  43         firstbit=MSB,
  44         sck=None,
  45         mosi=None,
  46         miso=None,
  47     ):
  48         """Initialize the Port"""
  49         self._port.set_frequency(baudrate)
  50         # FTDI device can only support mode 0 and mode 2
  51         # due to the limitation of MPSSE engine.
  52         # This means CPHA must = 0
  53         self._port._cpol = polarity
  54         if phase != 0:
  55             raise ValueError("Only SPI phase 0 is supported by FT232H.")
  56         self._port._cpha = phase
  57
  58     # pylint: enable=too-many-arguments
  59
  60     @property
  61     def frequency(self):
  62         """Return the current frequency"""
  63         return self._port.frequency
  64
  65     def write(self, buf, start=0, end=None):
  66         """Write data from the buffer to SPI"""
  67         end = end if end else len(buf)
  68         chunks, rest = divmod(end - start, self._spi.PAYLOAD_MAX_LENGTH)
  69         for i in range(chunks):
  70             chunk_start = start + i * self._spi.PAYLOAD_MAX_LENGTH
  71             chunk_end = chunk_start + self._spi.PAYLOAD_MAX_LENGTH
  72             self._port.write(buf[chunk_start:chunk_end])
  73         if rest:
  74             rest_start = start + chunks * self._spi.PAYLOAD_MAX_LENGTH
  75             self._port.write(buf[rest_start:end])
  76
  77     # pylint: disable=unused-argument
  78     def readinto(self, buf, start=0, end=None, write_value=0):
  79         """Read data from SPI and into the buffer"""
  80         end = end if end else len(buf)
  81         buffer_out = [write_value] * (end - start)
  82         result = self._port.exchange(buffer_out, end - start, duplex=True)
  83         for i, b in enumerate(result):
  84             buf[start + i] = b
  85
  86     # pylint: enable=unused-argument
  87
  88     # pylint: disable=too-many-arguments
  89     def write_readinto(
  90         self, buffer_out, buffer_in, out_start=0, out_end=None, in_start=0, in_end=None
  91     ):
  92         """Perform a half-duplex write from buffer_out and then
  93         read data into buffer_in
  94         """
  95         out_end = out_end if out_end else len(buffer_out)
  96         in_end = in_end if in_end else len(buffer_in)
  97         result = self._port.exchange(
  98             buffer_out[out_start:out_end], in_end - in_start, duplex=True
  99         )
 100         for i, b in enumerate(result):
 101             buffer_in[in_start + i] = b
 102
 103     # pylint: enable=too-many-arguments