Assuming these are 12bit signed numbers, then I think the answer is that you should extend the 12th bit out to the 16th bit position. The conversion should be 0..2047 (0x000..0x7FF) => 0..2047, and 0x4095..0x2048 (0xFFF..0x800) => -1..-2048. So, it is probably easier to keep the numbers less than 2096, and for those those bigger than 2047, subtract them from 4096 and negate. David Quoting "Schwab,Wilhelm K" <bschwab@anest.ufl.edu>:
Hello all,
I am trying to make a recognizer for a communication protocol that has very likely been errantly documented. Such tasks can be difficult enough with good docs, but I'm not even sure what is supposed to be happening, so it is really interesting.
One of the things that I **think** is happening, is that 12-bit two's complement data is included at one point in the stream. The bits are spread over a 16 bit word. Let's assume that I can correctly gather the 12 bits together. Could some kind soul suggest how to go from the resulting SmallInteger to the correct signed value? Smalltalk is adding a wrinkle that I am not sure how to handle: should I set the "missing" bits to 1? Out to bit 31?
Any pointers/suggestions would be greatly appreciated.
Bill
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