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mpu9250: Inline twos_complement() code 

Calling python functions can have high overhead.  Inline the
twos_complement code in the _extract_samples() inner loop.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2022-06-16 12:13:12 -04:00
parent 98a24172e7
commit 247a409335
1 changed files with 5 additions and 10 deletions
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15
klippy/extras/mpu9250.py
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@ -42,12 +42,6 @@ FIFO_SIZE = 512
Accel_Measurement = collections.namedtuple(
'Accel_Measurement', ('time', 'accel_x', 'accel_y', 'accel_z'))
# Helper method for getting the two's complement value of an unsigned int
def twos_complement(val, nbits):
if (val & (1 << (nbits - 1))) != 0:
val = val - (1 << nbits)
return val
MIN_MSG_TIME = 0.100
BYTES_PER_SAMPLE = 6
@ -139,11 +133,12 @@ class MPU9250:
for i in range(len(d) // BYTES_PER_SAMPLE):
d_xyz = d[i*BYTES_PER_SAMPLE:(i+1)*BYTES_PER_SAMPLE]
xhigh, xlow, yhigh, ylow, zhigh, zlow = d_xyz
rx = twos_complement(xhigh << 8 | xlow, 16)
ry = twos_complement(yhigh << 8 | ylow, 16)
rz = twos_complement(zhigh << 8 | zlow, 16)
raw_xyz = (rx, ry, rz)
# Merge and perform twos-complement
rx = ((xhigh << 8) | xlow) - ((xhigh & 0x80) << 9)
ry = ((yhigh << 8) | ylow) - ((yhigh & 0x80) << 9)
rz = ((zhigh << 8) | zlow) - ((zhigh & 0x80) << 9)
raw_xyz = (rx, ry, rz)
x = round(raw_xyz[x_pos] * x_scale, 6)
y = round(raw_xyz[y_pos] * y_scale, 6)
z = round(raw_xyz[z_pos] * z_scale, 6)