ADXL 345 (from Adafruit)

[Lokefar]

Has anyone already written a library for this sensor? Or are in the proces of doing so?
Am a bit lost at the moment on how to write the sensor driver.

The sensor is this one https://www.adafruit.com/products/1231

[livius]

@Lokefar
look here - should be simple to convert
https://github.com/pimoroni/adxl345-python/blob/master/adxl345.py

[Lokefar]

@livius Thanks. I will look into that one.

[Lokefar]

Have been trying to write a library for the sensor (Or at least a class that can be turned into a library), but I can't seem to get it to work. This is the code I have written and it is inspired by this https://github.com/pimoroni/adxl345-python/blob/master/adxl345.py

Any help would be greatly appreciated!

import time
from machine import I2C


ADXL345_ADDR = 0x53

i2c = I2C(0, I2C.MASTER, baudrate=100000)

BW_RATE_100HZ = 0x0B
POWER_CTL = 0x2D 
MEASURE = 0x08
DATA_FORMAT = 0x31
AXES_DATA = 0x32
BW_RATE = 0x2C
RANGE_2G = 0x00
SCALE_MULTIPLIER = 0.004
EARTH_GRAVITY_MS2 = 9.80665

class ADXL345(object):
	

	def __init__(self, i2c=None):
		self.i2c = i2c
		self.addr = ADXL345_ADDR
		print('One')
		self.setBandwidthRate(BW_RATE_100HZ)
		self.setRange(RANGE_2G)
		self.enableMeasurement()

	def enableMeasurement(self):
		i2c.writeto(self.addr, bytes(POWER_CTL))
		i2c.writeto(self.addr, bytes(MEASURE)) 

	def setBandwidthRate(self, rate_flag):
		print('Two')
		i2c.writeto_mem(self.addr, bytes(BW_RATE)

	def setRange(self, range_flag):
		value = i2c.readfrom_mem(self.addr, bytes(DATA_FORMAT))
		print('here')
		value &= ~0x0F;
		value |= range_flag;
		value |= 0x08;

		i2c.writeto(self.addr, DATA_FORMAT, value)

	def getAxes(self, gforce = False):
		bytes = i2c.readfrom(self.addr, AXES_DATA, 6)

		x = bytes[0] | (bytes[1] << 8)
		if(x & (1 << 16 - 1)):
			x = x - (1<<16)

		y = bytes[2] | (bytes[3] << 8)
		if(y & (1 << 16 - 1)):
			y = y - (1<<16)

		z = bytes[4] | (bytes[5] << 8 )
		if(z & (1 << 16 - 1)):
			z = z - (1<<16)

		x = x * SCALE_MULTIPLIER
		y = y * SCALE_MULTIPLIER
		z = z * SCALE_MULTIPLIER

		if gforce == False: 
			x = x * EARTH_GRAVITY_MS2
			y = y * EARTH_GRAVITY_MS2
			z = z * EARTH_GRAVITY_MS2

		x = round(x,4)
		y = round(y,4)
		z = round(z,4)

		return {"x": x, "y": y, "z": z}
print('Start')

for i in range(0,10):
	adxl345 = ADXL345()
	axes = adxl345.getAxes(True)
	print(axes['x'])
	sleep_ms(25)

Also for some reason the LED light on the expansion board has started to blink blue again.

[rikkertmark]

@Lokefar

I Think the heartbeat is Enabled

Please put the following code in your main.py or boot.py

import pycom

pycom.heartbeat(False)

I hope this is the solution for your blue light problem

[livius]

@Lokefar

i do not have this sensor to test but i have fixed some errors:

import time
from machine import I2C


ADXL345_ADDR = 0x53

i2c = I2C(0, I2C.MASTER, baudrate=100000)

BW_RATE_100HZ = 0x0B
POWER_CTL = 0x2D 
MEASURE = 0x08
DATA_FORMAT = 0x31
AXES_DATA = 0x32
BW_RATE = 0x2C
RANGE_2G = 0x00
SCALE_MULTIPLIER = 0.004
EARTH_GRAVITY_MS2 = 9.80665

class ADXL345(object):
	

	def __init__(self, i2c=None):
		self.i2c = i2c
		self.addr = ADXL345_ADDR
		print('One')
		self.setBandwidthRate(BW_RATE_100HZ)
		self.setRange(RANGE_2G)
		self.enableMeasurement()

	def enableMeasurement(self):
		i2c.writeto(self.addr, bytes([POWER_CTL]))
		i2c.writeto(self.addr, bytes([MEASURE])) 

	def setBandwidthRate(self, rate_flag):
		print('Two')
		i2c.writeto_mem(self.addr, BW_RATE, bytes([rate_flag]))

	def setRange(self, range_flag):
		value = i2c.readfrom_mem(self.addr, DATA_FORMAT, bytes([range_flag]))
		print('here')
		value &= ~0x0F;
		value |= range_flag;
		value |= 0x08;

		i2c.writeto(self.addr, DATA_FORMAT, value)

	def getAxes(self, gforce = False):
		bytes = i2c.readfrom(self.addr, AXES_DATA, 6)

		x = bytes[0] | (bytes[1] << 8)
		if(x & (1 << 16 - 1)):
			x = x - (1<<16)

		y = bytes[2] | (bytes[3] << 8)
		if(y & (1 << 16 - 1)):
			y = y - (1<<16)

		z = bytes[4] | (bytes[5] << 8 )
		if(z & (1 << 16 - 1)):
			z = z - (1<<16)

		x = x * SCALE_MULTIPLIER
		y = y * SCALE_MULTIPLIER
		z = z * SCALE_MULTIPLIER

		if gforce == False: 
			x = x * EARTH_GRAVITY_MS2
			y = y * EARTH_GRAVITY_MS2
			z = z * EARTH_GRAVITY_MS2

		x = round(x,4)
		y = round(y,4)
		z = round(z,4)

		return {"x": x, "y": y, "z": z}
print('Start')

for i in range(0,10):
	adxl345 = ADXL345()
	axes = adxl345.getAxes(True)
	print(axes['x'])
	sleep_ms(25)

[bucknall]

Hey @Lokefar this looks really cool! I'd love to add it to our libraries repository on GitHub!

When you finish and wish to share it, feel free to drop a pull request at https://github.com/pycom/pycom-libraries and we'll happily add it to our example library :)

[Lokefar]

@livius Thanks for the fixes. However, I still get an error:

  File "main.py", line 79, in <module>
  File "main.py", line 27, in __init__
  File "main.py", line 39, in setRange
TypeError: can't convert bytes to int

The problem seems to be with this line:

value = i2c.readfrom_mem(self.addr, DATA_FORMAT, bytes([range_flag]))

I noticed that you changed BW_RATE to an int instead of a hex. Tried changing DATA_FORMAT to 49 but that didn't solve the issue.

[Lokefar]

@bucknall Will do :)

[livius]

@Lokefar said in ADXL 345 (from Adafruit):

I noticed that you changed BW_RATE to an int instead of a hex. Tried changing DATA_FORMAT to 49 but that didn't solve the issue.

i revert this - this was only my try and forgot to revert

this line should be:

value = i2c.readfrom_mem(self.addr, DATA_FORMAT, range_flag)

[livius]

@Lokefar any progress? :)

[Lokefar]

@livius Yup I got it working. Just looking into cleaning up the code and add a few things then I will make it available for all to use :)

[arthurlutz]

@Lokefar I'm happy to help with clean up and testing your code.

[Divij Vignesh]

@Lokefar Can you post the final working code for this sensor with lopy 4?