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Add busio.I2C
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‎pslab/bus/busio.py

Lines changed: 187 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,187 @@
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"""Circuitpython's busio compatibility layer for pslab-python.
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This module emulates the CircuitPython's busio API for devices or hosts running
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CPython or MicroPython using pslab-python.
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This helps to access many sensors using Adafruit's drivers via PSLab board.
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Notes
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-----
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Documentation:
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https://circuitpython.readthedocs.io/en/6.3.x/shared-bindings/busio/index.html
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Examples
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--------
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Get humidity from Si7021 temperature and humidity sensor using adafruit_si7021 module.
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>>> import adafruit_si7021
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>>> from pslab.bus import busio # import board, busio
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>>> i2c = busio.I2C() # i2c = busio.I2C(board.SCL, board.SDA)
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>>> sensor = adafruit_si7021.SI7021(i2c)
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>>> print(sensor.relative_humidity)
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Get gyro reading from BNO055 using adafruit_bno055, board(just a wrapper for busio).
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>>> import adafruit_bno055
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>>> from pslab.bus import busio # import board
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>>> i2c = busio.I2C() # i2c = board.I2C()
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>>> sensor = adafruit_bno055.BNO055_I2C(i2c)
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>>> print(sensor.gyro)
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"""
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from typing import List, Union
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from pslab.bus.i2c import I2CPrimitive, I2CSlave
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from pslab.serial_handler import SerialHandler
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__all__ = "I2C"
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ReadableBuffer = Union[bytes, bytearray, memoryview]
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WriteableBuffer = Union[bytearray, memoryview]
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class I2C(I2CPrimitive):
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"""Busio I2C Class for CircuitPython Compatibility.
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Parameters
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----------
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device : :class:`SerialHandler`, optional
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Serial connection to PSLab device. If not provided, a new one will be
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created.
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frequency : float, optional
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Frequency of SCL in Hz.
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"""
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def __init__(self, device: SerialHandler = None, frequency: int = 125e3):
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# 125 kHz is as low as the PSLab can go.
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super().__init__(device)
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self._init()
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self._configure(frequency)
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def deinit(self) -> None:
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"""Just a dummy method."""
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pass
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def __enter__(self):
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"""Just a dummy method."""
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return self
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def __exit__(self, exc_type, exc_val, exc_tb) -> None:
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"""Just a dummy method."""
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self.deinit()
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def scan(self) -> List[int]:
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"""Scan all I2C addresses between 0x08 and 0x77 inclusive.
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Returns
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-------
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addrs : list of int
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List of 7-bit addresses on which slave devices replied.
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"""
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addrs = []
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for address in range(0x08, 0x77):
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slave = I2CSlave(address, self._device)
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if slave.ping():
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addrs.append(address)
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return addrs
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def try_lock(self) -> bool: # pylint: disable=no-self-use
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"""Just a dummy method."""
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return True
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def unlock(self) -> None:
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"""Just a dummy method."""
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pass
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def readfrom_into(
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self, address: int, buffer: WriteableBuffer, *, start: int = 0, end: int = None
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) -> None:
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"""Read from a device at specified address into a buffer.
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Parameters
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----------
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address : int
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7-bit I2C device address.
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buffer : bytearray or memoryview
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buffer to write into.
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start : int
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Index to start writing at.
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end : int
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Index to write up to but not include. Defaults to length of `buffer`.
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"""
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end = len(buffer) if end is None else end
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bytes_to_read = end - start
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self._start(address, 1)
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buffer[start:end] = self._read(bytes_to_read)
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self._stop()
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def writeto(
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self,
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address: int,
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buffer: ReadableBuffer,
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*,
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start: int = 0,
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end: int = None,
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stop: bool = True,
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) -> None:
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"""Write to a device at specified address from a buffer.
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Parameters
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----------
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address : int
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7-bit I2C device address.
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buffer : bytes or bytearray or memoryview
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buffer containing the bytes to write.
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start : int
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Index to start writing from.
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end : int
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Index to read up to but not include. Defaults to length of `buffer`.
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stop : bool
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Enable to transmit a stop bit. Defaults to True.
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"""
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end = len(buffer) if end is None else end
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if stop:
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self._write_bulk(address, buffer[start:end])
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else:
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self._start(address, 0)
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self._send(buffer[start:end])
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def writeto_then_readfrom(
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self,
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address: int,
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buffer_out: ReadableBuffer,
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buffer_in: WriteableBuffer,
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*,
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out_start: int = 0,
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out_end: int = None,
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in_start: int = 0,
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in_end: int = None,
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):
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"""Write to then read from a device at specified address.
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Parameters
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----------
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address : int
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7-bit I2C device address.
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out_buffer : bytes or bytearray or memoryview
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buffer containing the bytes to write.
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in_buffer : bytearray or memoryview
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buffer to write into.
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out_start : int
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Index to start writing from.
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out_end : int
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Index to read up to but not include. Defaults to length of `out_buffer`.
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in_start : int
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Index to start writing at.
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in_end : int
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Index to write up to but not include. Defaults to length of `in_buffer`.
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"""
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out_end = len(buffer_out) if out_end is None else out_end
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in_end = len(buffer_in) if in_end is None else in_end
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bytes_to_read = in_end - in_start
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self._start(address, 0)
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self._send(buffer_out[out_start:out_end])
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self._restart(address, 1)
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buffer_in[in_start:in_end] = self._read(bytes_to_read)
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self._stop()

‎pslab/bus/i2c.py

Lines changed: 36 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -24,6 +24,10 @@
2424
from pslab.serial_handler import SerialHandler
2525
from pslab.external.sensorlist import sensors
2626

27+
__all__ = (
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"I2CMaster",
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"I2CSlave",
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)
2731
logger = logging.getLogger(__name__)
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2933

@@ -42,6 +46,9 @@ class I2CPrimitive:
4246
_MIN_BRGVAL = 2
4347
_MAX_BRGVAL = 511
4448

49+
# Specs say typical delay is 110 ns to 130 ns; 150 ns from testing.
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_SCL_DELAY = 150e-9
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4552
_ACK = 0
4653
_READ = 1
4754
_WRITE = 0
@@ -56,23 +63,40 @@ def _init(self):
5663
self._device.send_byte(CP.I2C_INIT)
5764
self._device.get_ack()
5865

59-
def _configure(self, brgval: int):
60-
"""Configure bus brgval.
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def _configure(self, frequency: float):
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"""Configure bus frequency.
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6269
Parameters
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----------
64-
brgval : int
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Brgval of SCL in Hz.
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frequency : float
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Frequency of SCL in Hz.
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Raises
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------
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ValueError
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If given frequency is not supported by PSLab board.
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"""
79+
brgval = self._get_i2c_brgval(frequency)
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6781
if self._MIN_BRGVAL <= brgval <= self._MAX_BRGVAL:
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self._device.send_byte(CP.I2C_HEADER)
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self._device.send_byte(CP.I2C_CONFIG)
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self._device.send_int(brgval)
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self._device.get_ack()
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else:
73-
e = f"Brgval must be between {self._MIN_BRGVAL} and {self._MAX_BRGVAL}."
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min_frequency = self._get_i2c_frequency(self._MAX_BRGVAL)
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max_frequency = self._get_i2c_frequency(self._MIN_BRGVAL)
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e = f"Frequency must be between {min_frequency} and {max_frequency} Hz."
7490
raise ValueError(e)
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@classmethod
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def _get_i2c_brgval(cls, frequency: float) -> int:
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return int((1 / frequency - cls._SCL_DELAY) * CP.CLOCK_RATE - 2)
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@classmethod
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def _get_i2c_frequency(cls, brgval: int) -> float:
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return 1 / ((brgval + 2) / CP.CLOCK_RATE + cls._SCL_DELAY)
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76100
def _start(self, address: int, mode: int) -> int:
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"""Initiate I2C transfer.
78102
@@ -390,9 +414,6 @@ class I2CMaster(I2CPrimitive):
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created.
391415
"""
392416

393-
# Specs say typical delay is 110 ns to 130 ns; 150 ns from testing.
394-
_SCL_DELAY = 150e-9
395-
396417
def __init__(self, device: SerialHandler = None):
397418
super().__init__(device)
398419
self._init()
@@ -405,24 +426,13 @@ def configure(self, frequency: float):
405426
----------
406427
frequency : float
407428
Frequency of SCL in Hz.
408-
"""
409-
brgval = self._get_i2c_brgval(frequency)
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411-
if self._MIN_BRGVAL <= brgval <= self._MAX_BRGVAL:
412-
self._configure(brgval)
413-
else:
414-
min_frequency = self._get_i2c_frequency(self._MAX_BRGVAL)
415-
max_frequency = self._get_i2c_frequency(self._MIN_BRGVAL)
416-
e = f"Frequency must be between {min_frequency} and {max_frequency} Hz."
417-
raise ValueError(e)
418-
419-
@classmethod
420-
def _get_i2c_brgval(cls, frequency: float) -> int:
421-
return int((1 / frequency - cls._SCL_DELAY) * CP.CLOCK_RATE - 2)
422429
423-
@classmethod
424-
def _get_i2c_frequency(cls, brgval: int) -> float:
425-
return 1 / ((brgval + 2) / CP.CLOCK_RATE + cls._SCL_DELAY)
430+
Raises
431+
------
432+
ValueError
433+
If given frequency is not supported by PSLab board.
434+
"""
435+
self._configure(frequency)
426436

427437
def scan(self) -> List[int]:
428438
"""Scan I2C port for connected devices.
@@ -575,7 +585,7 @@ def write(self, bytes_to_write: bytearray, register_address: int = 0x0):
575585
----------
576586
bytes_to_write : bytearray
577587
Data to write to the slave.
578-
register_address : int
588+
register_address : int, optional
579589
Slave device internal memory address to write to. The default
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value is 0x0.
581591
"""

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