1  # The MIT License (MIT)
  2  #
  3  # Copyright (c) 2018 Dean Miller for Adafruit Industries
  4  #
  5  # Permission is hereby granted, free of charge, to any person obtaining a copy
  6  # of this software and associated documentation files (the "Software"), to deal
  7  # in the Software without restriction, including without limitation the rights
  8  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  9  # copies of the Software, and to permit persons to whom the Software is
 10  # furnished to do so, subject to the following conditions:
 11  #
 12  # The above copyright notice and this permission notice shall be included in
 13  # all copies or substantial portions of the Software.
 14  #
 15  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 18  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 19  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 20  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 21  # THE SOFTWARE.
 22  """
 23  `adafruit_epd.mcp_sram` - Adafruit MCP SRAM - sram driver
 24  ====================================================================================
 25  CircuitPython driver for Microchip SRAM chips
 26  * Author(s): Dean Miller
 27  """
 28  
 29  from micropython import const
 30  from adafruit_bus_device import spi_device
 31  
 32  __version__ = "0.0.0-auto.0"
 33  __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_EPD.git"
 34  
 35  SRAM_SEQUENTIAL_MODE = const(1 << 6)
 36  
 37  
 38  class Adafruit_MCP_SRAM_View:
 39      """A interface class that turns an SRAM chip into something like a memoryview"""
 40  
 41      def __init__(self, sram, offset):
 42          self._sram = sram
 43          self._offset = offset
 44          self._buf = [0]
 45  
 46      def __getitem__(self, i):
 47          return self._sram.read(self._offset + i, 1)[0]
 48  
 49      def __setitem__(self, i, val):
 50          self._buf[0] = val
 51          self._sram.write(self._offset + i, self._buf)
 52  
 53  
 54  class Adafruit_MCP_SRAM:
 55      """supporting class for communicating with
 56      Microchip SRAM chips"""
 57  
 58      SRAM_READ = 0x03
 59      SRAM_WRITE = 0x02
 60      SRAM_RDSR = 0x05
 61      SRAM_WRSR = 0x01
 62  
 63      def __init__(self, cs_pin, spi):
 64          # Handle hardware SPI
 65          self._spi = spi_device.SPIDevice(spi, cs_pin, baudrate=8000000)
 66          self.spi_device = spi
 67          self.cs_pin = cs_pin
 68          self._buf = bytearray(3)
 69          self._buf[0] = Adafruit_MCP_SRAM.SRAM_WRSR
 70          self._buf[1] = 0x43
 71          with self._spi as spidev:
 72              spidev.write(self._buf, end=2)  # pylint: disable=no-member
 73  
 74      def get_view(self, offset):
 75          """Create an object that can be used as a memoryview, with a given offset"""
 76          return Adafruit_MCP_SRAM_View(self, offset)
 77  
 78      def write(self, addr, buf, reg=SRAM_WRITE):
 79          """write the passed buffer to the passed address"""
 80          self._buf[0] = reg
 81          self._buf[1] = (addr >> 8) & 0xFF
 82          self._buf[2] = addr & 0xFF
 83  
 84          with self._spi as spi:
 85              spi.write(self._buf, end=3)  # pylint: disable=no-member
 86              spi.write(bytearray(buf))  # pylint: disable=no-member
 87  
 88      def read(self, addr, length, reg=SRAM_READ):
 89          """read passed number of bytes at the passed address"""
 90          self._buf[0] = reg
 91          self._buf[1] = (addr >> 8) & 0xFF
 92          self._buf[2] = addr & 0xFF
 93  
 94          buf = bytearray(length)
 95          with self._spi as spi:
 96              spi.write(self._buf, end=3)  # pylint: disable=no-member
 97              spi.readinto(buf)  # pylint: disable=no-member
 98          return buf
 99  
100      def read8(self, addr, reg=SRAM_READ):
101          """read a single byte at the passed address"""
102          return self.read(addr, 1, reg)[0]
103  
104      def read16(self, addr, reg=SRAM_READ):
105          """read 2 bytes at the passed address"""
106          buf = self.read(addr, 2, reg)
107          return buf[0] << 8 | buf[1]
108  
109      def write8(self, addr, value, reg=SRAM_WRITE):
110          """write a single byte at the passed address"""
111          self.write(addr, [value], reg)
112  
113      def write16(self, addr, value, reg=SRAM_WRITE):
114          """write 2 bytes at the passed address"""
115          self.write(addr, [value >> 8, value], reg)
116  
117      def erase(self, addr, length, value):
118          """erase the passed number of bytes starting at the passed address"""
119          self._buf[0] = Adafruit_MCP_SRAM.SRAM_WRITE
120          self._buf[1] = (addr >> 8) & 0xFF
121          self._buf[2] = addr & 0xFF
122          fill = bytearray([value])
123          with self._spi as spi:
124              spi.write(self._buf, end=3)  # pylint: disable=no-member
125              for _ in range(length):
126                  spi.write(fill)  # pylint: disable=no-member