Beaglebone and MMA7660FC accelerometer example in python

In this example we look at the MMA7660FC accelerometer connected to a Beaglebone

The MMA7660FC is a digital output I²C, very low-power, low-profile capacitive micro-machined accelerometer featuring a low pass filter, compensation for zero-g offset and gain errors and conversion to six-bit digital values at a user configurable output data rate. The device can be used for sensor data changes, product orientation and gesture detection through an interrupt pin (INT).

Features

Digital output I²C
3 mm x 3 mm x 0.9 mm DFN package
Low-power current consumption
- Off mode: 0.4 µA
- Standby mode: 2 µA
- Active mode: Configurable down to 47 µA
Low-voltage operation: 2.4 – 3.6-volts
3-axis ±1.5 g MEMS sensor and CMOS interface controller built into one package
Configurable output data rate from one to 120 samples a second
Auto wake/sleep feature for low-power consumption
Tilt orientation detection for portrait/landscape capability
Gesture detection including shake and pulse detection

Parts List

Part	Link
Beaglebone	BeagleBone Black TI AM335x Cortex-A8 development BB-Black Rev.C
MMA7660	IIC I2C MMA7660 Triaxial Acceleration Sensor Module For Arduino
Connecting wire	Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire

Connection

Beaglebone	MMA7660
3v3 – P9.3	Vcc
Gnd – P9.1	Gnd
SDA – P9.210	SDA
SCL – P9.19	SCL

Code

This is an example from controleverything called MMA7660FC.py

[codesyntax lang=”python”]

import smbus
import time

# Get I2C bus
bus = smbus.SMBus(2)

# MMA7660FC address, 0x4C(76)
# Select mode register, 0x07(07)
#		0x01(01)	Active mode
bus.write_byte_data(0x4C, 0x07, 0x01)
# MMA7660FC address, 0x4C(76)
# Select sample rate register, 0x08(08)
#		0x07(07)	1 Sample/second active
bus.write_byte_data(0x4C, 0x08, 0x07)

time.sleep(0.5)

# MMA7660FC address, 0x4C
# Read data back from 0x00, 3 bytes
# X-Axis Accl, Y-Axis Accl, Z-Axis Accl
data=bus.read_i2c_block_data(0x4C, 0x00, 3)

# Convert the data to 6-bits
xAccl = data[0] & 0x3F
if xAccl > 31 :
	xAccl -= 64

yAccl = data[1] & 0x3F
if yAccl > 31 :
	yAccl -= 64

zAccl = data[2] & 0x3F
if zAccl > 31 :
	zAccl -= 64

# Output data to screen
print "Acceleration in X-Axis : %d" %xAccl
print "Acceleration in Y-Axis : %d" %yAccl
print "Acceleration in Z-Axis : %d" %zAccl

[/codesyntax]

Output

run this by typing in

debian@beaglebone:/var/lib/cloud9/$ python mma7660.py
Acceleration in X-Axis : -10
Acceleration in Y-Axis : -19
Acceleration in Z-Axis : 0
debian@beaglebone:/var/lib/cloud9/$ python mma7660.py
Acceleration in X-Axis : -15
Acceleration in Y-Axis : -16
Acceleration in Z-Axis : -14
debian@beaglebone:/var/lib/cloud9/$ python mma7660.py
Acceleration in X-Axis : -20
Acceleration in Y-Axis : -4
Acceleration in Z-Axis : 15
debian@beaglebone:/var/lib/cloud9/$

Link

https://www.nxp.com/docs/en/data-sheet/MMA7660FC.pdf