ok, that was a false alarm. After looking again, it seems that the "sign" value not only switches between 0 and 255, but it also goes to 254 and to 1 (to indicate second lung).
This means that the actual range of the device is more than +/- 255. I expected to see it go to The max I've seen it get to on the "second lung" (that term is just too catchy to stop using!) is 190. So that's a total range of +/- 445.
@cherrybomb
At the moment, I've got code that checks for 255/254/0/1 etc, and act accordingly. However this is not the way to do it. It seems that this is not an 8 bit number after all, but actually a 10-bit, which is odd!
Using some bitwise operations, I think a much more elegant solution can be obtained. I'm having to go back to my elementary s/w engineering notes (5 years old, but still have them
)
Since we have 2 x 8 bit numbers, I'm thinking somethign along these lines:
The value for each axis in each direction ranges from:
00000000 (0)
11111111 (255)
and the "sign"/second lung figure is one of these four:
00000000 (0)
00000001 (1)
11111110 (254)
11111111 (255)
if we take just the last two bits from the sign:
00 (0)
01 (1)
10 (254)
11 (255)
and append that to the first 8 bits, to get a 10 bit number, then we look at the values, this would make things a much much more efficient, perofrmance and code wise. To test the theory, here are some values to see how it would work:
using 00000111 for the value (7), then we should be able to get the following figures.
0000000111 = 7
0100000111 = 263
1000000111 = -7 (if the first bit is read as a sign)
1100000111 = -263 (if the first bit is read as a sign)
and at this stage, we can check the MSB (most significant bit, far left) and that tells us the sign, then we shift everything to the left, and we'll have a value which we can multiply by -1 based on the MSB.
whaddaya think?