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

   1 """SPI Class for FTDI MPSSE"""
   2 from adafruit_blinka.microcontroller.ftdi_mpsse.mpsse.pin import Pin
   3 from adafruit_blinka.microcontroller.ftdi_mpsse.mpsse.url import (
   4     get_ft232h_url,
   5     get_ft2232h_url,
   6 )
   7
   8 # pylint: disable=protected-access
   9 class SPI:
  10     """Custom SPI Class for FTDI MPSSE"""
  11
  12     MSB = 0
  13
  14     def __init__(self, spi_id=None):
  15         # pylint: disable=import-outside-toplevel
  16         from pyftdi.spi import SpiController
  17
  18         # pylint: enable=import-outside-toplevel
  19
  20         self._spi = SpiController(cs_count=1)
  21         if spi_id is None:
  22             self._spi.configure(get_ft232h_url())
  23         else:
  24             self._spi.configure(get_ft2232h_url(spi_id + 1))
  25         self._port = self._spi.get_port(0)
  26         self._port.set_frequency(100000)
  27         self._port._cpol = 0
  28         self._port._cpha = 0
  29         # Change GPIO controller to SPI
  30         Pin.mpsse_gpio = self._spi.get_gpio()
  31
  32     # pylint: disable=too-many-arguments,unused-argument
  33     def init(
  34         self,
  35         baudrate=100000,
  36         polarity=0,
  37         phase=0,
  38         bits=8,
  39         firstbit=MSB,
  40         sck=None,
  41         mosi=None,
  42         miso=None,
  43     ):
  44         """Initialize the Port"""
  45         self._port.set_frequency(baudrate)
  46         # FTDI device can only support mode 0 and mode 2
  47         # due to the limitation of MPSSE engine.
  48         # This means CPHA must = 0
  49         self._port._cpol = polarity
  50         if phase != 0:
  51             raise ValueError("Only SPI phase 0 is supported by FT232H.")
  52         self._port._cpha = phase
  53
  54     # pylint: enable=too-many-arguments
  55
  56     @property
  57     def frequency(self):
  58         """Return the current frequency"""
  59         return self._port.frequency
  60
  61     def write(self, buf, start=0, end=None):
  62         """Write data from the buffer to SPI"""
  63         end = end if end else len(buf)
  64         chunks, rest = divmod(end - start, self._spi.PAYLOAD_MAX_LENGTH)
  65         for i in range(chunks):
  66             chunk_start = start + i * self._spi.PAYLOAD_MAX_LENGTH
  67             chunk_end = chunk_start + self._spi.PAYLOAD_MAX_LENGTH
  68             self._port.write(buf[chunk_start:chunk_end])
  69         if rest:
  70             rest_start = start + chunks * self._spi.PAYLOAD_MAX_LENGTH
  71             self._port.write(buf[rest_start:end])
  72
  73     # pylint: disable=unused-argument
  74     def readinto(self, buf, start=0, end=None, write_value=0):
  75         """Read data from SPI and into the buffer"""
  76         end = end if end else len(buf)
  77         buffer_out = [write_value] * (end - start)
  78         result = self._port.exchange(buffer_out, end - start, duplex=True)
  79         for i, b in enumerate(result):
  80             buf[start + i] = b
  81
  82     # pylint: enable=unused-argument
  83
  84     # pylint: disable=too-many-arguments
  85     def write_readinto(
  86         self, buffer_out, buffer_in, out_start=0, out_end=None, in_start=0, in_end=None
  87     ):
  88         """Perform a half-duplex write from buffer_out and then
  89         read data into buffer_in
  90         """
  91         out_end = out_end if out_end else len(buffer_out)
  92         in_end = in_end if in_end else len(buffer_in)
  93         result = self._port.exchange(
  94             buffer_out[out_start:out_end], in_end - in_start, duplex=True
  95         )
  96         for i, b in enumerate(result):
  97             buffer_in[in_start + i] = b
  98
  99     # pylint: enable=too-many-arguments