How To Connect Adxl345 To Raspberry Pi Pico
Made by mahmood-m-shilleh
About the project
In this tutorial learn how to connect the ADXL345 to the Raspberry Pi Pico to get real acceleration values.
Project info
Difficulty: Easy
Platforms: MicroPython
Estimated time: 1 hour
License: GNU Lesser General Public License version 3 or later (LGPL3+)
Items used in this project
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1-) Step One: Physical Connection
Setup pins as follows for I2C connection, you only need 4 jumper wires. You can get the sensor and Raspberry Pi pre-soldered or solder them yourself. This is sufficient enough to start getting sensor values! Be sure not to mix power connections as this can fry the sensor.
2-) Step Two: CodeRun the following code in MicroPython:
from machine import Pin, I2C
import time
import ustruct
# Constants
ADXL345_ADDRESS = 0x53 # address for accelerometer
ADXL345_POWER_CTL = 0x2D # address for power control
ADXL345_DATA_FORMAT = 0x31 # configure data format
ADXL345_DATAX0 = 0x32 # where the x-axis data starts
# Initialize I2C
i2c = I2C(0, sda=Pin(0), scl=Pin(1), freq=400000)
# Initialize ADXL345
def init_adxl345():
i2c.writeto_mem(ADXL345_ADDRESS, ADXL345_POWER_CTL, bytearray([0x08])) # Set bit 3 to 1 to enable measurement mode
i2c.writeto_mem(ADXL345_ADDRESS, ADXL345_DATA_FORMAT, bytearray([0x0B])) # Set data format to full resolution, +/- 16g
# Read acceleration data
def read_accel_data():
data = i2c.readfrom_mem(ADXL345_ADDRESS, ADXL345_DATAX0, 6)
x, y, z = ustruct.unpack('<3h', data)
return x, y, z
# Main loop
init_adxl345()
while True:
x, y, z = read_accel_data()
print('--------------------')
print(x, y, z) # raw values from sensor
print("X: {}, Y: {}, Z: {}".format(x*0.0039, y*0.0039, z*0.0039))
time.sleep(0.5)
# if you do get OSError: [Errno 5] EIO, try unplug and plug
# if you do set different resolution 0.0039 may not be the constant (check data sheet)If you set everything up properly you should start seeing values in x, y, and z in units of g (9.81 m/s^2).
Some takeaways from the code:- Gives you acceleration values up to 16g. You can adjust this by changing the bytearray you pass into the DATA_FORMAT register.
- You can calibrate your sensor for more accurate results. ShillehTek has a video on this already here.
- If you do get OSError trying unplugging and plugging the Pico in.
- 0.0039 is retrieved from the ADXL345 datasheet, this value changes depending on the resolution you select
- You can extend this and calculate the angle with some trigonometry, another tutorial will be made on this topic.
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Credits
mahmood-m-shilleh
Mechanical and Software Engineering Background. University at Buffalo 2019 Texas A&M 2021 I make data pipelines for my day job. Outside of work, I participate in online communities regarding Full Stack Engineering, Microelectronics, and more. You can find more details about me on my Youtube Channel. https://www.youtube.com/@mmshilleh Feel free to reach out!
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