从 16 位宽寄存器中选择一个引脚，python

Question

[Inputs]：

地址：0x001c，16 位宽。

重置：0x0

这是 PIN 16..31 的位字段寄存器。

[问题]：如何选择 PIN 17？

[我的解决方案]：这是正确的做法吗：

def select_pin(pin):
lowstate = 0x0000
highstate = 0x001c
pin_hex = int(str(pin), 16)
responsive = highstate-pin_hex
inverted = hex(responsive ^ 0xFFFF)
print(inverted)
select_pin(17)

老实说，我对这个领域有一个理论差距，我什至不确定如何制定我的问题以在 Google 中找到有关它的一些信息，任何帮助将不胜感激。

Answer 1

假设(寄存器(值位表示引脚值，其中每个引脚号表示LSB->MSB(从右到左(的位索引，您所要做的就是简单的按位和介于：

• 价值
• 一个掩码，它只设置了一个位(在所需引脚的位置(，而所有其他位都被重置

要提取您感兴趣的位(PIN( 值，请执行以下操作：

>>> reg = 0x001C0000  # Hi Word, Lo Word
>>>
>>> reg_bin_repr = "{0:032b}".format(0x001C0000)  # For visualization purposes only
>>> reg_bin_repr
'00000000000111000000000000000000'
>>>
>>> for idx, val in enumerate(reversed(reg_bin_repr)):  # Each bit with its value (right -> left)
...     print("Bit (pin) {0:02d}: {1:s}".format(idx, val))
...
Bit (pin) 00: 0
Bit (pin) 01: 0
Bit (pin) 02: 0
Bit (pin) 03: 0
Bit (pin) 04: 0
Bit (pin) 05: 0
Bit (pin) 06: 0
Bit (pin) 07: 0
Bit (pin) 08: 0
Bit (pin) 09: 0
Bit (pin) 10: 0
Bit (pin) 11: 0
Bit (pin) 12: 0
Bit (pin) 13: 0
Bit (pin) 14: 0
Bit (pin) 15: 0
Bit (pin) 16: 0
Bit (pin) 17: 0
Bit (pin) 18: 1
Bit (pin) 19: 1
Bit (pin) 20: 1
Bit (pin) 21: 0
Bit (pin) 22: 0
Bit (pin) 23: 0
Bit (pin) 24: 0
Bit (pin) 25: 0
Bit (pin) 26: 0
Bit (pin) 27: 0
Bit (pin) 28: 0
Bit (pin) 29: 0
Bit (pin) 30: 0
Bit (pin) 31: 0
>>>
>>> # And the function
>>> def pin_value(register_value, pin_number):
...     return 1 if register_value & (1 << pin_number) else 0
...
>>>
>>> pin_value(reg, 17)
0
>>> pin_value(reg, 18)
1

作为旁注，在处理数字时，您不必将它们转换为相同的基数，将其转换为不同的基数时，值不会更改，只有其表示形式会更改：

>>> i0 = 1
>>> i1 = 0x19
>>>
>>> i0 + i1
26
>>> i1
25
>>> hex(i1)
'0x19'
>>> int(hex(i1), 16)
25

Answer 2

位掩码只是以整数表示法2**pin。

如果您有

# alternating increasing amounts of 0/1
reg = int("10110011100011110000111110000010",2)  # 4294967295
def get_pin(value, pin):
return 1 if (value & 2**pin) > 0 else 0 
for p in range(33):
print(f"{2**p:>10} is {get_pin(reg,p)}")
1 is 0
2 is 1
4 is 0
8 is 0
16 is 0
32 is 0
64 is 0
128 is 1
256 is 1
512 is 1
1024 is 1
2048 is 1
4096 is 0
8192 is 0
16384 is 0
32768 is 0
65536 is 1
131072 is 1
262144 is 1
524288 is 1
1048576 is 0
2097152 is 0
4194304 is 0
8388608 is 1
16777216 is 1
33554432 is 1
67108864 is 0
134217728 is 0
268435456 is 1
536870912 is 1
1073741824 is 0
2147483648 is 1