Non-POSIX parity (mark/space) with Python-Serial on Linux.

[Grant Edwards]

On 2011-11-21, David Riley <fraveydank at gmail.com> wrote:
> On Nov 21, 2011, at 2:29 PM, Matthew Lenz wrote:
>
>> Another thing I noticed is that the & and | appear to give the same result as adding or subtracting 128 from the ordinal value.  I'm assuming that isn't coincidence. :)
>
> It's not, though the difference is important.  They're binary ANDs (&) and ORs (|), so (0x0F | 0x80) = 0x8F, but (0x8F | 0x80) = 0x8F as well, whereas (0x8F + 0x80) = 0x10F.  For manipulating bit values (which is what you're doing, you should almost never be adding or subtracting, but rather ANDing and ORing (or XORing, but not nearly as often).
>
> Just in case you're not familiar, 0x is the prefix for a hexadecimal number. 0x80 = 128, which is binary 10000000 (i.e. the high bit in a byte).

Like the old joke:

  There are 10 kinds of people in the world: those who understand
  binary numbers, and those who don't.

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Grant Edwards               grant.b.edwards        Yow! ... I don't like FRANK
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