94 lines
2.9 KiB
Python
94 lines
2.9 KiB
Python
# SPDX-FileCopyrightText: 2021 Melissa LeBlanc-Williams for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""Generic Linux I2C class using PureIO's smbus class"""
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from Adafruit_PureIO import smbus
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class I2C:
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"""I2C class"""
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MASTER = 0
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SLAVE = 1
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_baudrate = None
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_mode = None
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_i2c_bus = None
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# pylint: disable=unused-argument
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def __init__(self, bus_num, mode=MASTER, baudrate=None):
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if mode != self.MASTER:
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raise NotImplementedError("Only I2C Master supported!")
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_mode = self.MASTER
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# if baudrate != None:
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# print("I2C frequency is not settable in python, ignoring!")
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try:
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self._i2c_bus = smbus.SMBus(bus_num)
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except FileNotFoundError:
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raise RuntimeError(
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"I2C Bus #%d not found, check if enabled in config!" % bus_num
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) from RuntimeError
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# pylint: enable=unused-argument
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def scan(self):
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"""Try to read a byte from each address, if you get an OSError
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it means the device isnt there"""
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found = []
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for addr in range(0, 0x80):
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try:
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self._i2c_bus.read_byte(addr)
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except OSError:
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continue
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found.append(addr)
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return found
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# pylint: disable=unused-argument
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def writeto(self, address, buffer, *, start=0, end=None, stop=True):
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"""Write data from the buffer to an address"""
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if end is None:
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end = len(buffer)
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self._i2c_bus.write_bytes(address, buffer[start:end])
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def readfrom_into(self, address, buffer, *, start=0, end=None, stop=True):
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"""Read data from an address and into the buffer"""
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if end is None:
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end = len(buffer)
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readin = self._i2c_bus.read_bytes(address, end - start)
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for i in range(end - start):
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buffer[i + start] = readin[i]
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# pylint: enable=unused-argument
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def writeto_then_readfrom(
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self,
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address,
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buffer_out,
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buffer_in,
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*,
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out_start=0,
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out_end=None,
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in_start=0,
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in_end=None,
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stop=False
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):
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"""Write data from buffer_out to an address and then
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read data from an address and into buffer_in
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"""
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if out_end is None:
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out_end = len(buffer_out)
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if in_end is None:
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in_end = len(buffer_in)
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if stop:
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# To generate a stop in linux, do in two transactions
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self.writeto(address, buffer_out, start=out_start, end=out_end, stop=True)
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self.readfrom_into(address, buffer_in, start=in_start, end=in_end)
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else:
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# To generate without a stop, do in one block transaction
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readin = self._i2c_bus.read_i2c_block_data(
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address, buffer_out[out_start:out_end], in_end - in_start
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)
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for i in range(in_end - in_start):
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buffer_in[i + in_start] = readin[i]
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