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
   4 # pylint: disable=protected-access
   5 class SPI:
   6     """Custom SPI Class for FTDI MPSSE"""
   7
   8     MSB = 0
   9
  10     def __init__(self, spi_id=None):
  11         # pylint: disable=import-outside-toplevel
  12         from pyftdi.spi import SpiController
  13
  14         # pylint: enable=import-outside-toplevel
  15
  16         self._spi = SpiController(cs_count=1)
  17         if spi_id is None:
  18             self._spi.configure("ftdi://ftdi:ft232h/1")
  19         else:
  20             self._spi.configure("ftdi://ftdi:ft2232h/{}".format(spi_id + 1))
  21         self._port = self._spi.get_port(0)
  22         self._port.set_frequency(100000)
  23         self._port._cpol = 0
  24         self._port._cpha = 0
  25         # Change GPIO controller to SPI
  26         Pin.mpsse_gpio = self._spi.get_gpio()
  27
  28     # pylint: disable=too-many-arguments,unused-argument
  29     def init(
  30         self,
  31         baudrate=100000,
  32         polarity=0,
  33         phase=0,
  34         bits=8,
  35         firstbit=MSB,
  36         sck=None,
  37         mosi=None,
  38         miso=None,
  39     ):
  40         """Initialize the Port"""
  41         self._port.set_frequency(baudrate)
  42         # FTDI device can only support mode 0 and mode 2
  43         # due to the limitation of MPSSE engine.
  44         # This means CPHA must = 0
  45         self._port._cpol = polarity
  46         if phase != 0:
  47             raise ValueError("Only SPI phase 0 is supported by FT232H.")
  48         self._port._cpha = phase
  49
  50     # pylint: enable=too-many-arguments
  51
  52     @property
  53     def frequency(self):
  54         """Return the current frequency"""
  55         return self._port.frequency
  56
  57     def write(self, buf, start=0, end=None):
  58         """Write data from the buffer to SPI"""
  59         end = end if end else len(buf)
  60         chunks, rest = divmod(end - start, self._spi.PAYLOAD_MAX_LENGTH)
  61         for i in range(chunks):
  62             chunk_start = start + i * self._spi.PAYLOAD_MAX_LENGTH
  63             chunk_end = chunk_start + self._spi.PAYLOAD_MAX_LENGTH
  64             self._port.write(buf[chunk_start:chunk_end])
  65         if rest:
  66             rest_start = start + chunks * self._spi.PAYLOAD_MAX_LENGTH
  67             self._port.write(buf[rest_start:end])
  68
  69     # pylint: disable=unused-argument
  70     def readinto(self, buf, start=0, end=None, write_value=0):
  71         """Read data from SPI and into the buffer"""
  72         end = end if end else len(buf)
  73         buffer_out = [write_value] * (end - start)
  74         result = self._port.exchange(buffer_out, end - start, duplex=True)
  75         for i, b in enumerate(result):
  76             buf[start + i] = b
  77
  78     # pylint: enable=unused-argument
  79
  80     # pylint: disable=too-many-arguments
  81     def write_readinto(
  82         self, buffer_out, buffer_in, out_start=0, out_end=None, in_start=0, in_end=None
  83     ):
  84         """Perform a half-duplex write from buffer_out and then
  85         read data into buffer_in
  86         """
  87         out_end = out_end if out_end else len(buffer_out)
  88         in_end = in_end if in_end else len(buffer_in)
  89         result = self._port.exchange(
  90             buffer_out[out_start:out_end], in_end - in_start, duplex=True
  91         )
  92         for i, b in enumerate(result):
  93             buffer_in[in_start + i] = b
  94
  95     # pylint: enable=too-many-arguments