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_ft2232h_url,
   9 )
  10
  11 # pylint: disable=protected-access
  12 class SPI:
  13     """Custom SPI Class for FTDI MPSSE"""
  14
  15     MSB = 0
  16
  17     def __init__(self, spi_id=None):
  18         # pylint: disable=import-outside-toplevel
  19         from pyftdi.spi import SpiController
  20
  21         # pylint: enable=import-outside-toplevel
  22
  23         self._spi = SpiController(cs_count=1)
  24         if spi_id is None:
  25             self._spi.configure(get_ft232h_url())
  26         else:
  27             self._spi.configure(get_ft2232h_url(spi_id + 1))
  28         self._port = self._spi.get_port(0)
  29         self._port.set_frequency(100000)
  30         self._port._cpol = 0
  31         self._port._cpha = 0
  32         # Change GPIO controller to SPI
  33         Pin.mpsse_gpio = self._spi.get_gpio()
  34
  35     # pylint: disable=too-many-arguments,unused-argument
  36     def init(
  37         self,
  38         baudrate=100000,
  39         polarity=0,
  40         phase=0,
  41         bits=8,
  42         firstbit=MSB,
  43         sck=None,
  44         mosi=None,
  45         miso=None,
  46     ):
  47         """Initialize the Port"""
  48         self._port.set_frequency(baudrate)
  49         # FTDI device can only support mode 0 and mode 2
  50         # due to the limitation of MPSSE engine.
  51         # This means CPHA must = 0
  52         self._port._cpol = polarity
  53         if phase != 0:
  54             raise ValueError("Only SPI phase 0 is supported by FT232H.")
  55         self._port._cpha = phase
  56
  57     # pylint: enable=too-many-arguments
  58
  59     @property
  60     def frequency(self):
  61         """Return the current frequency"""
  62         return self._port.frequency
  63
  64     def write(self, buf, start=0, end=None):
  65         """Write data from the buffer to SPI"""
  66         end = end if end else len(buf)
  67         chunks, rest = divmod(end - start, self._spi.PAYLOAD_MAX_LENGTH)
  68         for i in range(chunks):
  69             chunk_start = start + i * self._spi.PAYLOAD_MAX_LENGTH
  70             chunk_end = chunk_start + self._spi.PAYLOAD_MAX_LENGTH
  71             self._port.write(buf[chunk_start:chunk_end])
  72         if rest:
  73             rest_start = start + chunks * self._spi.PAYLOAD_MAX_LENGTH
  74             self._port.write(buf[rest_start:end])
  75
  76     # pylint: disable=unused-argument
  77     def readinto(self, buf, start=0, end=None, write_value=0):
  78         """Read data from SPI and into the buffer"""
  79         end = end if end else len(buf)
  80         buffer_out = [write_value] * (end - start)
  81         result = self._port.exchange(buffer_out, end - start, duplex=True)
  82         for i, b in enumerate(result):
  83             buf[start + i] = b
  84
  85     # pylint: enable=unused-argument
  86
  87     # pylint: disable=too-many-arguments
  88     def write_readinto(
  89         self, buffer_out, buffer_in, out_start=0, out_end=None, in_start=0, in_end=None
  90     ):
  91         """Perform a half-duplex write from buffer_out and then
  92         read data into buffer_in
  93         """
  94         out_end = out_end if out_end else len(buffer_out)
  95         in_end = in_end if in_end else len(buffer_in)
  96         result = self._port.exchange(
  97             buffer_out[out_start:out_end], in_end - in_start, duplex=True
  98         )
  99         for i, b in enumerate(result):
 100             buffer_in[in_start + i] = b
 101
 102     # pylint: enable=too-many-arguments