Incorrect results

[jaminturner]

Incorrect results

[AlekseyFedorovich]

My setup (that works) for converting bits to g units is:

twentybits         = 1048576  # max int for 20 bits
scale_factor       = 1.95E-6
g_range = 2  # can be 2, 4, 8
# join 3 bytes and remove last four bits (data is 20 bits)
x = (buf[0] << 16 | buf[1] << 8 | buf[2]) >> 4
# twos complements
if x >= (twentybits / 2): 
    x = x - twentybits
# conversion in g units
x = x * g_range * scale_factor