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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_CTRL_REG1_ADDR = const(0x20)
LIS302DL_OUT_X = const(0x29)
# Configuration for 100Hz sampling rate, +-2g range
LIS302DL_CONF = 0b01000111
def signed8(x):
if x & 0x80:
return x - 256
else:
return x
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.wr(LIS302DL_CTRL_REG1_ADDR, bytearray([LIS302DL_CONF]))
def rd(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
self.cs_pin.high()
return buf
def wr(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.rd(LIS302DL_WHO_AM_I_ADDR, 1)
def get_xyz(self):
val = self.rd(LIS302DL_OUT_X, 5)
x = signed8(val[0]) * 18.0 / 1000
y = signed8(val[2]) * 18.0 / 1000
z = signed8(val[4]) * 18.0 / 1000
return [x, y, z]
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