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@sorz /MMA7455L.py
Last active Dec 17, 2015

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Read acceleration from MMA7455L via I2C by Python.
#!/usr/bin/env python
import smbus
import time
class Accel():
def __init__(self, dev=1, g=2):
self.bus = smbus.SMBus(dev)
self.set_range(g)
def write(self, register, data):
self.bus.write_byte_data(0x1D, register, data)
def read(self, data):
return self.bus.read_byte_data(0x1D, data)
def set_range(self, g):
if g == 8:
d = 0b01000001
elif g == 4:
d = 0b01001001
elif g == 2:
d = 0b01000101
else:
raise ValueError("Only 2, 4 or 8.")
self.write(0x16, d)
self.g = g
def _get(self, addr):
l = self.read(addr)
h = self.read(addr + 1)
d = h << 8 | l
if d > 511:
d -= 1024
return d
def get_x(self):
return self._get(0x00)
def get_y(self):
return self._get(0x02)
def get_z(self):
return self._get(0x04)
def clear_offset(self):
self.write(0x10, 0)
self.write(0x11, 0)
self.write(0x12, 0)
self.write(0x13, 0)
self.write(0x14, 0)
self.write(0x15, 0)
time.sleep(0.1)
def _set_offset(self, addr, zero):
d = self._get(addr - 0x10)
d = zero - d
d = int(d * 2.5)
d += 65536
self.write(addr, d & 0xff) # Low
self.write(addr + 1, d >> 8 & 0xff) # High
def set_offset(self):
self.clear_offset()
self._set_offset(0x10, 0)
self._set_offset(0x12, 0)
if self.g == 4:
zero = 32
else:
zero = 64
self._set_offset(0x14, zero)
time.sleep(0.1)
def main():
mma = Accel(1)
mma.set_offset()
while True:
x = mma.get_x()
y = mma.get_y()
z = mma.get_z()
print("x =%4d ,y =%4d, z =%4d" % (x, y, z))
time.sleep(0.1)
if __name__ == '__main__':
main()
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