Tag Archives: CubieTruck

Synchronize the time in ROS offline environments without chrony

As our [amazon &title=CubieTruck&text=CubieTruck] is faced with strange issues when using chrony and internet access is not a general prerequisite on ROS setups, i needed to figure out a new way to synchronize the time with no internet ntp server available. For some reasons, even my local ntp was broken, which is why I try to set the time according to the ros master on all clients by this simple bash command:

it simply extracts the IPv4 part of the $ROS_MASTER_URI environment and uses ntpdate to set the time on the excecuting client system.

In case you only want to know the exact time derivation consider using the ntpdate parameter -q which only emulates the request.

Using Chrony on CubieTruck

Don’t.

Unless you really know what are you doing.

To synchronize the clock and fix a minimal time shift I was detecting, I followed the idea of the TurtleBot2 to use chrony to fix that Chrony is a little daemon that connects to your linux clock or hwclock and detect shifts. For some reason this lead to total chaos on the amosero.
I suppose chrony hasn’t been build for multicore dynamically speeded processors like the A20, which is why the shifting has been erratic and up to 2 seconds per minute.

sudo apt-get remove chrony

Fixed all timing errors on the [amazon &title=CubieTruck&text=CubieTruck]. Also it’s a bit disturbing how little changes can inflict complex setups.

 

 

Sketch him up!

Today I am trying to setup all parts of the coming robot. Because assembling and disassembling would take hours until finding the right configuration and saving steps in between it would be impossible – I thought of a better way. Using my shopworn SketchUp skills and way more time than I expected – finally there is a non perfect but practicable model with the most important parts that are going to be installed. All of them already have the correct physical dimensions which also means that it would be possible to deploy the robot in rviz later, or at least parts of it.

Here are some early stage impressions:

CubiBot1

concept phase: iso view

The wireframe boxes are space required by usb plugs or power jacks. These need to be accessible and can’t be blocked by anything else.

This robot is not ready yet, everything needs to be rearranged and boxed soon. Some parts are still missing, and no cables are shown, so everything will be more packed than it looks like.

Ultrasonic Sensor HC-SR04 as a ROS Range publisher

I’ve taken a HC-SR04 like shown below and connected it to the CubieTruck as a rosserial publisher.

IMG_20140512_114741

 

Instead a of a simple  std_msgs::String str_msg;  I’ve implemented a  sensor_msgs::Range range_msg; which after starting the arduino in ros with rosrun rosserial_python serial_node.py /dev/ttyACM0 shows up in  rostopic echo /ultrasound like this:

So with that, its possible to visualize everything using rqt_plot:

ScreenshotROSUltraSound

which is pretty nice for my first arduino micro ros project and less than an two hours of work 🙂

For further information see here

 

Howto use CubieTruck and NetworkManager to do WPA2 Enterprise TLS

Last days the [amazon &title=CubieTruck&text=CubieTruck] made me struggle with its Network behavior. It continuously refused to connect to any WLAN, didn’t allow the Usage of the NetworkManager GUI, and confused me a lot.

Some things that might help you:

Wlan isn’t enabled by default – or at least it wasn’t for me.

Load the driver

In case you don’t want to do that everytime the [amazon &title=CubieTruck&text=CubieTruck] needs wifi consider adding a new line with ‘bcmdhd’ (no quotes) to /etc/modules

I needed to install the linux firmware:

and reboot

3. bring the wlan0 device up and scan if your wlan is available

Check if the /etc/network/interfaces file looks something like that:

No additional lines, or the NetworkManager will struggle with your devices, showing them as “not managed” or “disconnected”.

So by default lubuntu 13.04 image, no Network manager has been running by boot, so I’ve fixed that by adding following line to my /etc/crontab:

(sure there are other ways – especially because it’s a system service)

So after reboot – using the [amazon &title=CubieTruck&text=CubieTruck]-GUI its faces you with a “Network Manager not running”.

Screenshot[amazon &title=CubieTruck&text=CubieTruck]

So the small Icon on the taskbar isn’t able to find the network manager.
I could not fix that other than by opening an LXTerminal and:

which leads me to a nice WLAN GUI and made it possible to use WPA2 Enterprise with TLS 🙂