mc3479

MC3479 Accelerometer Driver

• Author(s): Jose D. Montoya

Implementation Notes

Software and Dependencies:

• Adafruit CircuitPython firmware for the supported boards: https://circuitpython.org/downloads

• Adafruit’s Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice

• Adafruit’s Register library: https://github.com/adafruit/Adafruit_CircuitPython_Register

class mc3479.MC3479(i2c_bus: I2C, address: int = _I2C_ADDR)

Driver for the MC3479 Sensor connected over I2C.

Parameters:

• i2c_bus (I2C) – The I2C bus the MC3479 is connected to.

• address (int) – The I2C device address. Defaults to 0x4C

Raises:

RuntimeError – if the sensor is not found

Quickstart: Importing and using the device

Here is an example of using the MC3479 class. First you will need to import the libraries to use the sensor

import board
import mc3479 as MC3479

Once this is done you can define your board.I2C object and define your sensor object

i2c = board.I2C()  # Uses board.SCL and board.SDA
mc3479 = MC3479.MC3479(i2c)

Now you have access to the attributes

accx, accy, accz = mc3479.acceleration

property acceleration: Tuple[int, int, int]

The device has the ability to read all sampled readings in a continuous sampling fashion. The device always updates the XOUT, YOUT, and ZOUT registers at the chosen output data rate

X, Y, and Z-axis accelerometer measurements are in 16-bit, signed 2’s complement format. Register addresses 0x0D to 0x12 hold the latest sampled data from the X, Y, and Z accelerometers.

property acceleration_output_data_rate: int

Define the output data rate in Hz The output data rate is dependent of the power mode setting for the sensor

Mode	Value
MC3479.BANDWIDTH_25	0x10 25 Hz
MC3479.BANDWIDTH_50	0x11 50 Hz
MC3479.BANDWIDTH_62_5	0x12 62.5 Hz
MC3479.BANDWIDTH_100	0x13 100 Hz
MC3479.BANDWIDTH_125	0x14 125 Hz
MC3479.BANDWIDTH_250	0x15 250 Hz
MC3479.BANDWIDTH_500	0x16 500 Hz
MC3479.BANDWIDTH_1000	0x17 1000 Hz

Example

i2c = board.I2C()
mc3479 = MC3479.MC3479(i2c)
mc3479.acceleration_output_data_rate = MC3479.BANDWIDTH_500

property acceleration_range: int

The range and scale control register sets the resolution, range, and filtering options for the accelerometer. All values are in sign-extended 2’s complement format. Values are reported in registers 0x0D – 0x12 (the hardware formats the output)

Mode	Value
MC3479.ACCEL_RANGE_2G	0b000
MC3479.ACCEL_RANGE_4G	0b001
MC3479.ACCEL_RANGE_8G	0b010
MC3479.ACCEL_RANGE_16G	0b011
MC3479.ACCEL_RANGE_12G	0b100

Example

i2c = board.I2C()
mc3479 = MC3479.MC3479(i2c)
mc3479.acceleration_range = MC3479.ACCEL_RANGE_12G

property lpf_enabled: int

Low Power Filter Enabler

Mode	Value
MC3479.LPF_ENABLE	0b0
MC3479.LPF_DISABLE	0b1

Example

i2c = board.I2C()
mc3479 = MC3479.MC3479(i2c)
mc3479.lpf_enabled = MC3479.LPF_ENABLE

property lpf_setting: int

Selects the Bandwidth for the Low Power Filter. Depends on the selection of the ODR/IDR

Mode	Value
MC3479.BANDWIDTH_1	0b001 Fc = IDR / 4.255
MC3479.BANDWIDTH_2	0b010 Fc = IDR / 6
MC3479.BANDWIDTH_3	0b010 Fc = IDR / 12
MC3479.BANDWIDTH_5	0b010 Fc = IDR / 16

Example

i2c = board.I2C()
mc3479 = MC3479.MC3479(i2c)

mc3479.lpf_setting = MC3479.BANDWIDTH_5

property sensor_mode: int

Standby

• Lowest power consumption

• Internal clocking is halted

• No motion detection, sampling, or calibration

• The I2C/SPI bus can read and write to registers (resolution, range, thresholds and other settings can be changed)

• Reset not allowed

• Default state after a power-up

Normal

• Highest power consumption

• Internal clocking is enabled

• Continuous motion detection and sampling; automatic calibration is available

• The I2C/SPI bus can only write to the mode register and read all other registers

• Reset allowed

Mode	Value
MC3479.STANDBY	0
MC3479.NORMAL	1