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Handle multi-byte registers with aplomb #21

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Merged
merged 3 commits into from
Feb 15, 2019
Merged

Handle multi-byte registers with aplomb #21

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ed766a4
bitmask is now within the byte defined for the bit
ladyada Feb 14, 2019
695205d
handle multibyte (but not straddling' bits)
ladyada Feb 14, 2019
9a8090a
linted
ladyada Feb 14, 2019
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4 changes: 2 additions & 2 deletions adafruit_register/i2c_bit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,10 +43,10 @@ class RWBit:
:param int register_width: The number of bytes in the register. Defaults to 1.
"""
def __init__(self, register_address, bit, register_width=1):
self.bit_mask = 1 << bit
self.bit_mask = 1 << (bit%8) # the bitmask *within* the byte!
self.buffer = bytearray(1 + register_width)
self.buffer[0] = register_address
self.byte = bit // 8 + 1
self.byte = bit // 8 + 1 # the byte number within the buffer

def __get__(self, obj, objtype=None):
with obj.i2c_device as i2c:
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9 changes: 5 additions & 4 deletions adafruit_register/i2c_bits.py
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Expand Up @@ -48,12 +48,13 @@ def __init__(self, num_bits, register_address, lowest_bit, register_width=1):
self.bit_mask = 0
for _ in range(num_bits):
self.bit_mask = (self.bit_mask << 1) + 1
self.bit_mask = self.bit_mask << lowest_bit
if self.bit_mask >= (1 << 8):
raise ValueError()
self.bit_mask = self.bit_mask << (lowest_bit%8)
if self.bit_mask >= 0xFF:
raise ValueError("Cannot have more bits than fit in a single byte")

self.buffer = bytearray(1 + register_width)
self.buffer[0] = register_address
self.lowest_bit = lowest_bit
self.lowest_bit = lowest_bit % 8 # lowest bit within byte
self.byte = lowest_bit // 8 + 1

def __get__(self, obj, objtype=None):
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