kopia lustrzana https://github.com/peterhinch/micropython_eeprom
93 wiersze
3.8 KiB
Python
93 wiersze
3.8 KiB
Python
# eeprom_i2c.py MicroPython driver for Microchip I2C EEPROM devices.
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# Released under the MIT License (MIT). See LICENSE.
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# Copyright (c) 2019 Peter Hinch
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import time
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from micropython import const
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from bdevice import BlockDevice
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_ADDR = const(0x50) # Base address of chip
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_MAX_CHIPS_COUNT = const(8) # Max number of chips
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T24C512 = const(65536) # 64KiB 512Kbits
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T24C256 = const(32768) # 32KiB 256Kbits
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T24C128 = const(16384) # 16KiB 128Kbits
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T24C64 = const(8192) # 8KiB 64Kbits
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T24C32 = const(4096) # 4KiB 32Kbits
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# Logical EEPROM device consists of 1-8 physical chips. Chips must all be the
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# same size, and must have contiguous addresses.
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class EEPROM(BlockDevice):
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def __init__(self, i2c, chip_size=T24C512, verbose=True, block_size=9):
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self._i2c = i2c
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if chip_size not in (T24C32, T24C64, T24C128, T24C256, T24C512):
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print("Warning: possible unsupported chip. Size:", chip_size)
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nchips, min_chip_address = self.scan(verbose, chip_size) # No. of EEPROM chips
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super().__init__(block_size, nchips, chip_size)
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self._min_chip_address = min_chip_address
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self._i2c_addr = 0 # I2C address of current chip
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self._buf1 = bytearray(1)
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self._addrbuf = bytearray(2) # Memory offset into current chip
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# Check for a valid hardware configuration
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def scan(self, verbose, chip_size):
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devices = self._i2c.scan() # All devices on I2C bus
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eeproms = [d for d in devices if _ADDR <= d < _ADDR + _MAX_CHIPS_COUNT] # EEPROM chips
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nchips = len(eeproms)
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if nchips == 0:
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raise RuntimeError("EEPROM not found.")
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eeproms = sorted(eeproms)
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if len(set(eeproms)) != len(eeproms):
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raise RuntimeError('Duplicate addresses were found', eeproms)
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if (eeproms[-1] - eeproms[0] + 1) != len(eeproms):
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raise RuntimeError('Non-contiguous chip addresses', eeproms)
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if verbose:
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s = "{} chips detected. Total EEPROM size {}bytes."
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print(s.format(nchips, chip_size * nchips))
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return nchips, min(eeproms)
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def _wait_rdy(self): # After a write, wait for device to become ready
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self._buf1[0] = 0
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while True:
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try:
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if self._i2c.writeto(self._i2c_addr, self._buf1): # Poll ACK
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break
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except OSError:
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pass
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finally:
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time.sleep_ms(1)
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# Given an address, set ._i2c_addr and ._addrbuf and return the number of
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# bytes that can be processed in the current page
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def _getaddr(self, addr, nbytes): # Set up _addrbuf and _i2c_addr
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if addr >= self._a_bytes:
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raise RuntimeError("EEPROM Address is out of range")
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ca, la = divmod(addr, self._c_bytes) # ca == chip no, la == offset into chip
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self._addrbuf[0] = (la >> 8) & 0xFF
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self._addrbuf[1] = la & 0xFF
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self._i2c_addr = self._min_chip_address + ca
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pe = (addr & ~0x7F) + 0x80 # byte 0 of next page
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return min(nbytes, pe - la)
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# Read or write multiple bytes at an arbitrary address
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def readwrite(self, addr, buf, read):
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nbytes = len(buf)
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mvb = memoryview(buf)
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start = 0 # Offset into buf.
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while nbytes > 0:
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npage = self._getaddr(addr, nbytes) # No. of bytes in current page
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assert npage > 0
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if read:
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self._i2c.writeto(self._i2c_addr, self._addrbuf)
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self._i2c.readfrom_into(self._i2c_addr, mvb[start : start + npage])
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else:
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self._i2c.writevto(
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self._i2c_addr, (self._addrbuf, buf[start : start + npage])
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)
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self._wait_rdy()
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nbytes -= npage
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start += npage
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addr += npage
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return buf
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