Installation¶

How to get started with a set of MyoMuscles, Ganglia and Flexray2USBAdapter.

Cabling and Power¶

Warning

Check if:

all motor cables are plugged in correctly. There are 2 ribbon cables (grey and rainbow coloured) that connect each motor with its motor driver board
all sensor displacement cables are plugged in correctly
all motor driver boards are connected to power with common ground and power is turned off
all motor driver boards are connected to their respective ganglion (via SPI)
all joint sensors are connected to ganglia
all ganglia are connected to power with common ground and power is turned off
all ganglia are connected to the flexray bus
all power supplies are set to output at the very most 24V (for basic testing the 13 muscle MyoArm will run off a single 3A power supply)
the Flexray2USB adapter is connected to power with common ground and power is turned off
the Flexray2USB adapter is connected to the flexray bus
turn the power on and check if
- all driver boards are lighting/flashing green
- the joint has a blinking light whose frequency changes with the joint’s angular displacement
the software starts

Software Installation¶

To get started we recommend installing both the myo_blink and ros_control_boilerplate fork examples on top of the required flexrayusbinterface.

These examples require ROS kinetic to be installed on Ubuntu 16.04.

Allow your user to access the serial device¶

By default Ubuntu does not let you access your serial adapters. To change that we will add your user to the group ‘dialout’. Execute the following in a terminal:

sudo usermod -a -G dialout $(whoami)

This only needs to be done once.

Create a new workspace¶

Create a new folder that will contain your ROS / catkin workspace and all code.

source /opt/ros/kinetic/setup.bash
mkdir -p ~/MyoArm_ws/src && cd MyoArm_ws/src && catkin_init_workspace
cd ..
catkin_make

Now add the workspace to your ~/.bashrc so that it gets automatically sourced upon opening a shell:

echo 'source ~/MyoArm_ws/devel/setup.bash' >> ~/.bashrc

Install flexrayusbinterface¶

roscd && cd ../src
git clone https://github.com/roboy/flexrayusbinterface.git -b develop
roscd flexrayusbinterface && ./install_deps.sh

Important

The ftd2xx driver does not get loaded automatically. In order to use it you need to either install our udev rules [1] (recommended):

roscd flexrayusbinterface && sudo ./install_udev_rules.sh

Or manually unload the standard drivers every time you re-plug the Flexray2USBInterface board:

sudo rmmod ftdi_sio
sudo rmmod usbserial

Install myo_blink¶

Clone¶

roscd && cd ../src
git clone https://github.com/roboy/myo_blink.git -b master

Configure the myo_blink software example.¶

All system configuration is placed inside a yaml file in the ‘config’ directory of this package. Most importantly it contains the serial number of the USB2Flexray adapter. Adjust it to your devices ID.

Hint

Find your device mounting location in /dev

All unix systems treat everything (including devices) as files. So first we want to find where your Ubuntu has mounted the USB2Flexray adapter.

Unplug the USB cable of the USB2Flexray adapter and in a terminal do one by one:
ls -1 /dev > ~/before.txt

# Plug the UBS cable back in

ls -1 /dev > ~/after.txt

diff ~/before.txt ~/after.txt
You should see a few lines, one of which should start with:
> ttyUSBn
Where ‘n’ is a number: This is the device location.

ttyUSBn is the name of your USB device (i. e. ttyUSB1). It has been mounted at /dev/ as /dev/ttyUSBn now let’s:

Find the device’s serial number

Use the following command, but replace the ttyUSBn with the above found name starting with ttyUSB:
/bin/udevadm info --name=/dev/ttyUSBn | grep SERIAL_SHORT
The returned string is the unique serial of the USB2FLEXRAY adapter, please copy it.

Update the .yaml file

Replace the string after the tag serial: in the yaml file located in the config directory of the myo_blink package with the newly found serial.

Install ros_control_boilerplate fork¶

roscd && cd ../src
git clone https://github.com/compiaffe/ros_control_boilerplate.git -b MyoArm

Important

Also set the serial number in the corresponding yaml file as per Configure the myo_blink software example.. The yaml file is placed in

roscd ros_control_boilerplate/rrbot_control/config

Install all ROS dependencies¶

apt-get install -y ros-kinetic-rosparam-shortcuts ros-kinetic-ros-control ros-kinetic-ros-controllers ros-kinetic-control-msgs ros-kinetic-urdf ros-kinetic-control-toolbox ros-kinetic-robot-state-publisher libgflags-dev libncurses5-dev libncursesw5-dev wget vim

Build it¶

roscd && cd ..
catkin_make

ROS’ plentitute of terminals¶

For using ROS effectively, you will need a large number of terminals open at the same time. I recommend using the terminal app: terminator. Here you can split the screen into multiple terminals or add tabs. Once it is installed, see what a right-click allows you to do.

Install it using:

sudo apt-get install terminator -y

Run it using the myo_blink example application¶

In different (terminator) terminals run:

source .../MyoArm/devel/setup.bash

Then one of the following:

roscore
roslaunch myo_blink myo_blink.launch
rostopic list

For the last one you should now see a list of 13 topics starting with /myo_blink/muscles/

To see the state of a muscle you need to subscribe to its topic: Every muscle has a topic where it publishes it’s state. These are the 13 topics found above.

i.e. listen to the topic of the biceps muscle as follows:

rostopic echo -c /myo_blink/muscles/biceps

Important

Please note, that nothing will be published on these topics before you have sent any command to the motor!

In order to control a motor you need to send a rosservice call to it in a new console:

rosservice call /myo_blink/move "muscle: 'biceps'
action: 'move with'
setpoint: 0.0"

Important

When typing the rosservice call parameters autocomplete is your friend: Start by typing rosservice call /myo_blink/move and then press tab once or twice. ROS will autocomplete your text as good as it can. All you still need to do is fill in the action, to one of the options shown below and type in a setpoint.

Control mode (action):

‘move to’ - PositionController
‘move with’ - VelocityController
‘keep’ - Effort / ForceController

[1]	The udev rules are based on this article: https://www.ikalogic.com/ftdi-d2xx-linux-overcoming-big-problem/