118 lines
3.9 KiB
Python
118 lines
3.9 KiB
Python
# SPDX-FileCopyrightText: 2018 Dean Miller for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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`adafruit_epd.mcp_sram` - Adafruit MCP SRAM - sram driver
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====================================================================================
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CircuitPython driver for Microchip SRAM chips
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* Author(s): Dean Miller
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"""
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from micropython import const
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from adafruit_bus_device import spi_device
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try:
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"""Needed for type annotations"""
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from typing import Any, List
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from digitalio import DigitalInOut
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from busio import SPI
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except ImportError:
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pass
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__version__ = "0.0.0+auto.0"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_EPD.git"
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SRAM_SEQUENTIAL_MODE = const(1 << 6)
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class Adafruit_MCP_SRAM_View:
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"""An interface class that turns an SRAM chip into something like a memoryview"""
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def __init__(self, sram: int, offset: int) -> None:
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self._sram = sram
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self._offset = offset
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self._buf = [0]
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def __getitem__(self, i: int) -> Any:
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return self._sram.read(self._offset + i, 1)[0]
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def __setitem__(self, i: int, val: Any) -> None:
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self._buf[0] = val
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self._sram.write(self._offset + i, self._buf)
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class Adafruit_MCP_SRAM:
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"""supporting class for communicating with
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Microchip SRAM chips"""
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SRAM_READ = 0x03
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SRAM_WRITE = 0x02
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SRAM_RDSR = 0x05
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SRAM_WRSR = 0x01
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def __init__(self, cs_pin: DigitalInOut, spi: SPI):
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# Handle hardware SPI
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self._spi = spi_device.SPIDevice(spi, cs_pin, baudrate=8000000)
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self.spi_device = spi
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self.cs_pin = cs_pin
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self._buf = bytearray(3)
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self._buf[0] = Adafruit_MCP_SRAM.SRAM_WRSR
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self._buf[1] = 0x43
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with self._spi as spidev:
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spidev.write(self._buf, end=2) # pylint: disable=no-member
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def get_view(self, offset: int) -> Adafruit_MCP_SRAM_View:
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"""Create an object that can be used as a memoryview, with a given offset"""
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return Adafruit_MCP_SRAM_View(self, offset)
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def write(self, addr: int, buf: List, reg=SRAM_WRITE):
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"""write the passed buffer to the passed address"""
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self._buf[0] = reg
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self._buf[1] = (addr >> 8) & 0xFF
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self._buf[2] = addr & 0xFF
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with self._spi as spi:
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spi.write(self._buf, end=3) # pylint: disable=no-member
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spi.write(bytearray(buf)) # pylint: disable=no-member
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def read(self, addr: int, length: int, reg: int = SRAM_READ):
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"""read passed number of bytes at the passed address"""
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self._buf[0] = reg
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self._buf[1] = (addr >> 8) & 0xFF
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self._buf[2] = addr & 0xFF
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buf = bytearray(length)
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with self._spi as spi:
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spi.write(self._buf, end=3) # pylint: disable=no-member
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spi.readinto(buf) # pylint: disable=no-member
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return buf
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def read8(self, addr: int, reg: int = SRAM_READ):
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"""read a single byte at the passed address"""
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return self.read(addr, 1, reg)[0]
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def read16(self, addr: int, reg: int = SRAM_READ):
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"""read 2 bytes at the passed address"""
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buf = self.read(addr, 2, reg)
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return buf[0] << 8 | buf[1]
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def write8(self, addr: int, value: int, reg: int = SRAM_WRITE):
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"""write a single byte at the passed address"""
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self.write(addr, [value], reg)
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def write16(self, addr: int, value: int, reg: int = SRAM_WRITE):
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"""write 2 bytes at the passed address"""
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self.write(addr, [value >> 8, value], reg)
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def erase(self, addr: int, length: int, value: Any):
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"""erase the passed number of bytes starting at the passed address"""
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self._buf[0] = Adafruit_MCP_SRAM.SRAM_WRITE
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self._buf[1] = (addr >> 8) & 0xFF
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self._buf[2] = addr & 0xFF
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fill = bytearray([value])
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with self._spi as spi:
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spi.write(self._buf, end=3) # pylint: disable=no-member
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for _ in range(length):
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spi.write(fill) # pylint: disable=no-member
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