1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
|
# SPDX-FileCopyrightText: 2017 Scott Shawcroft for Adafruit Industries
#
# SPDX-License-Identifier: MIT
# pylint: disable=too-few-public-methods
"""
`adafruit_register.i2c_struct_array`
====================================================
Array of structured registers based on `struct`
* Author(s): Scott Shawcroft
"""
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_Register.git"
import struct
try:
from typing import Tuple, Optional, Type
from circuitpython_typing.device_drivers import I2CDeviceDriver
except ImportError:
pass
class _BoundStructArray:
"""
Array object that `StructArray` constructs on demand.
:param object obj: The device object to bind to. It must have a `i2c_device` attribute
:param int register_address: The register address to read the bit from
:param str struct_format: The struct format string for each register element
:param int count: Number of elements in the array
"""
def __init__(
self,
obj: I2CDeviceDriver,
register_address: int,
struct_format: str,
count: int,
) -> None:
self.format = struct_format
self.first_register = register_address
self.obj = obj
self.count = count
def _get_buffer(self, index: int) -> bytearray:
"""Shared bounds checking and buffer creation."""
if not 0 <= index < self.count:
raise IndexError()
size = struct.calcsize(self.format)
# We create the buffer every time instead of keeping the buffer (which is 32 bytes at least)
# around forever.
buf = bytearray(size + 1)
buf[0] = self.first_register + size * index
return buf
def __getitem__(self, index: int) -> Tuple:
buf = self._get_buffer(index)
with self.obj.i2c_device as i2c:
i2c.write_then_readinto(buf, buf, out_end=1, in_start=1)
return struct.unpack_from(self.format, buf, 1) # offset=1
def __setitem__(self, index: int, value: Tuple) -> None:
buf = self._get_buffer(index)
struct.pack_into(self.format, buf, 1, *value)
with self.obj.i2c_device as i2c:
i2c.write(buf)
def __len__(self) -> int:
return self.count
class StructArray:
"""
Repeated array of structured registers that are readable and writeable.
Based on the index, values are offset by the size of the structure.
Values are tuples that map to the values in the defined struct. See struct
module documentation for struct format string and its possible value types.
.. note:: This assumes the device addresses correspond to 8-bit bytes. This is not suitable for
devices with registers of other widths such as 16-bit.
:param int register_address: The register address to begin reading the array from
:param str struct_format: The struct format string for this register.
:param int count: Number of elements in the array
"""
def __init__(self, register_address: int, struct_format: str, count: int) -> None:
self.format = struct_format
self.address = register_address
self.count = count
self.array_id = "_structarray{}".format(register_address)
def __get__(
self,
obj: Optional[I2CDeviceDriver],
objtype: Optional[Type[I2CDeviceDriver]] = None,
) -> _BoundStructArray:
# We actually can't handle the indexing ourself due to data descriptor limits. So, we return
# an object that can instead. This object is bound to the object passed in here by its
# initializer and then cached on the object itself. That way its lifetime is tied to the
# lifetime of the object itself.
if not hasattr(obj, self.array_id):
setattr(
obj,
self.array_id,
_BoundStructArray(obj, self.address, self.format, self.count),
)
return getattr(obj, self.array_id)
|