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Testing a Phidget Accelerometer
Description: This tutorial shows you how to connect a Phidget accelerometer and view axes data changes published to a ROS topic.Keywords: phidgets, accelerometer
Tutorial Level: BEGINNER
One Time Setup Instructions
The phidgets_ros package calls phidgets_py_api which loads the Phidgets C Api (phidgetspp_c_api). On linux, by default, USB devices are not writeable by anybody but root. This can be solved by following the udev ruleset instructions in the phidgetspp_c_api package. You will need to build this package to get the instructions and the rule file:
$ roscd phidgetspp_c_api $ rosmake
Following the udev instructions in build/Phidgetlinux/README file.
$ sudo cp build/Phidgetlinux/phidget21/udev/*.rules /etc/udev/rules.d/.
then restart udev:
$ sudo /etc/init.d/udev restart
You will also need to set up one last environment variable so that libusb will look at /dev/bus/usb instead of /proc/bus/usb.
$ export USB_DEVFS_PATH=/dev/bus/usb
After this, you should be able to connect your Phidget.
Compiling
Start by compiling the driver:
$ rosmake phidgets_ros
To Run
Run the Accelerometer node. (You might be prompted to start roscore in another shell if it is not already running.)
$ rosrun phidgets_ros accelerometer.py
You should see something like this:
Please attach Accelerometer now. (waiting 15 seconds)
Connect a Phidget Accelerometer using a USB cable to your PC.
Confirming Accelerometer Output
Move the accelerometer to create data changes. To monitor the changes, echo the accelerometer ROS topic:
$ rostopic list $ rostopic echo /accelerometer
You should see something like this:
--- index: 2 acceleration: 1.74697995186 --- index: 2 acceleration: 0.960539996624 --- index: 2 acceleration: 0.413670003414 --- index: 1 acceleration: 0.547490000725 --- index: 2 acceleration: 1.27319002151 --- index: 0 acceleration: 0.571290016174
Note: Index 0, 1 and 2 are the x, y and z axes. Which axes the index numbers coorespond to will vary depending on how you mount the accelerometer.
