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"""
Driver for accelerometer on STM32F4 Discover board.
Assumes it's a LIS302DL MEMS device.
Sets accelerometer range at +-2g.
Returns list containing X,Y,Z axis acceleration values in 'g' units (9.8m/s^2).
See:
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/Components/lis302dl/lis302dl.h
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/Components/lis302dl/lis302dl.c
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/STM32F4-Discovery/stm32f4_discovery.c
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/STM32F4-Discovery/stm32f4_discovery.h
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/STM32F4-Discovery/stm32f4_discovery_accelerometer.c
STM32Cube_FW_F4_V1.1.0/Drivers/BSP/STM32F4-Discovery/stm32f4_discovery_accelerometer.h
STM32Cube_FW_F4_V1.1.0/Projects/STM32F4-Discovery/Demonstrations/Src/main.c
"""
from pyb import Pin
from pyb import SPI
READWRITE_CMD = const(0x80)
MULTIPLEBYTE_CMD = const(0x40)
LIS302DL_WHO_AM_I_ADDR = const(0x0f)
LIS302DL_WHO_AM_I_VAL = const(0x3b)
LIS302DL_CTRL_REG1_ADDR = const(0x20)
LIS302DL_OUT_X = const(0x29)
LIS302DL_OUT_Y = const(0x2b)
LIS302DL_OUT_Z = const(0x2d)
# Configuration for 100Hz sampling rate, +-2g range
LIS302DL_CONF = const(0b01000111)
def convert_raw_to_g(x):
if x & 0x80:
x = x - 256
return x * 18 / 1000
class STAccel:
def __init__(self):
self.cs_pin = Pin('PE3', Pin.OUT_PP, Pin.PULL_NONE)
self.cs_pin.high()
self.spi = SPI(1, SPI.MASTER, baudrate=328125, polarity=0, phase=1, bits=8)
self.write_bytes(LIS302DL_CTRL_REG1_ADDR, bytearray([LIS302DL_CONF]))
if self.read_id() != LIS302DL_WHO_AM_I_VAL:
raise Exception('LIS302DL accelerometer not present')
def read_bytes(self, addr, nbytes):
if nbytes > 1:
addr |= READWRITE_CMD | MULTIPLEBYTE_CMD
else:
addr |= READWRITE_CMD
self.cs_pin.low()
self.spi.send(addr)
#buf = self.spi.send_recv(bytearray(nbytes * [0])) # read data, MSB first
buf = self.spi.recv(nbytes)
self.cs_pin.high()
return buf
def write_bytes(self, addr, buf):
if len(buf) > 1:
addr |= MULTIPLEBYTE_CMD
self.cs_pin.low()
self.spi.send(addr)
for b in buf:
self.spi.send(b)
self.cs_pin.high()
def read_id(self):
return self.read_bytes(LIS302DL_WHO_AM_I_ADDR, 1)[0]
def x(self):
return convert_raw_to_g(self.read_bytes(LIS302DL_OUT_X, 1)[0])
def y(self):
return convert_raw_to_g(self.read_bytes(LIS302DL_OUT_Y, 1)[0])
def z(self):
return convert_raw_to_g(self.read_bytes(LIS302DL_OUT_Z, 1)[0])
def xyz(self):
val = self.read_bytes(LIS302DL_OUT_X, 5)
return [convert_raw_to_g(val[0]),
convert_raw_to_g(val[2]),
convert_raw_to_g(val[4])]
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