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ADXL345 range setting on micropython
Posted: Tue Feb 04, 2020 3:33 pm
by davidbogatec
I want to set the 16g range of the accelerometer. The default range is 2G. Where I need to specify this in the below code?
Code: Select all
from machine import Pin,I2C
import math
import time
device = const(0x53)
regAddress = const(0x32)
TO_READ = 6
buff = bytearray(6)
class ADXL345:
def __init__(self,i2c,addr=device):
self.addr = addr
self.i2c = i2c
b = bytearray(1)
b[0] = 0
self.i2c.writeto_mem(self.addr,0x2d,b)
b[0] = 16
self.i2c.writeto_mem(self.addr,0x2d,b)
b[0] = 8
self.i2c.writeto_mem(self.addr,0x2d,b)
@property
def xValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
x = (int(buff[1]) << 8) | buff[0]
if x > 32767:
x -= 65536
return x
@property
def yValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
y = (int(buff[3]) << 8) | buff[2]
if y > 32767:
y -= 65536
return y
@property
def zValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
z = (int(buff[5]) << 8) | buff[4]
if z > 32767:
z -= 65536
return z
def RP_calculate(self,x,y,z):
roll = math.atan2(y , z) * 57.3
pitch = math.atan2((- x) , math.sqrt(y * y + z * z)) * 57.3
return roll,pitch
Re: ADXL345 range setting on micropython
Posted: Tue Feb 04, 2020 6:38 pm
by cgglzpy
Hi,
You can see this in the data sheet:
ADXL345
[Page 26-27] Register 0x31—DATA_FORMAT (Read/Write) --> Range Bits D1-D0
So you need to write to register 0x31 the byte 0x03 which is 0b00000011 (see Table 21) setting bits D1-D0 to 1.
In code should be something like:
and inside 'def __init__' method add:
Code: Select all
b[0] = 3
self.i2c.writeto_mem(self.addr,reg_DATA_FORMAT,b)
I can't test this but I think this is the way.
Re: ADXL345 range setting on micropython
Posted: Wed Feb 05, 2020 8:46 am
by davidbogatec
Hi cgglpzy and thanks for your prompt reply.
i've insert the suggested lines in the code but nothing happens.
Where is the error?
from machine import Pin,I2C
import math
import time
device = const(0x53)
regAddress = const(0x32)
TO_READ = 6
buff = bytearray(6)
reg_DATA_FORMAT = const(0x31)
class ADXL345:
def __init__(self,i2c,addr=device):
self.addr = addr
self.i2c = i2c
b = bytearray(1)
b[0] = 0
self.i2c.writeto_mem(self.addr,0x2d,b)
b[0] = 16
self.i2c.writeto_mem(self.addr,0x2d,b)
b[0] = 8
self.i2c.writeto_mem(self.addr,0x2d,b)
b[0] = 3
self.i2c.writeto_mem(self.addr,reg_DATA_FORMAT,b)
@property
def xValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
x = (int(buff[1]) << 8) | buff[0]
if x > 32767:
x -= 65536
return x
@property
def yValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
y = (int(buff[3]) << 8) | buff[2]
if y > 32767:
y -= 65536
return y
@property
def zValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
z = (int(buff[5]) << 8) | buff[4]
if z > 32767:
z -= 65536
return z
def RP_calculate(self,x,y,z):
roll = math.atan2(y , z) * 57.3
pitch = math.atan2((- x) , math.sqrt(y * y + z * z)) * 57.3
return roll,pitch
Re: ADXL345 range setting on micropython
Posted: Thu Feb 06, 2020 3:58 pm
by cgglzpy
i've insert the suggested lines in the code but nothing happens.
Hmm, maybe because of this
From the data sheet Page 26:
All data, except that for the ±16 g range, must be clipped to avoid rollover
So I think you have to comment or erase the "if x > 32767" lines.
Something like this:
Code: Select all
def xValue(self):
buff = self.i2c.readfrom_mem(self.addr,regAddress,TO_READ)
x = (int(buff[1]) << 8) | buff[0]
# if x > 32767: # These two lines is to "clip" the data to avoid rollover
# x -= 65536 # They are necessary for ranges 2g-8g but not for 16g range
return x
Also do the same with yValue and zValue methods.
If this does not solve it then I don't know what can it be
