ev3dev Access Point

This repo contains instructions and an Ansible script to set up an ev3dev image that will make a Lego Mindstorms EV3 robot and a Netgear WBNA1100 WiFi dongle act as a standalone access point that a tablet or laptop can connect to.

This is useful for demos or classroom activities where the overhead of having to connect to a local WiFi network is too much. Obviously, neither the EV3 or the tablet/latop can connect to the internet when this approach is used -- although the EV3 can make use of the micro-USB cable CDC connection to do this when necessary.

Firstly here are some manual steps to create the base SD card image and to set up the CDC network connection. The rest is automatically provisioned using an Ansible script. Please note that since Ansible does not officially support running from Windows, that these are focused on running from Mac OS X.

SD Card Setup

You will need a suitable Micro SD card. The EV3 supports SDHC version 2.0 (max 32 GB). SDHC v2 means that it can manage transfer rates of up to 25MB/s which is essentially Class 10. 8GB is more than enough space.

The manual steps are largely based on following the Mac version of the ev3dev.org Getting Started instructions from http://www.ev3dev.org/docs/getting-started/ .

1. Download the image file https://github.com/ev3dev/ev3dev/releases/download/ev3dev-jessie-2015-12-30/ev3-ev3dev-jessie-2015-12-30.img.zip

2. Copy to the SD card (on a Mac) following http://www.ev3dev.org/docs/tutorials/writing-sd-card-image-mac-command-line/

   diskutil list

   plug in card

   diskutil list

   carefully check which disk number corresponds to the card

   TRIPLE CHECK that the disk number is correct before running this!

   if you have an external drive, for example, it may be disk2!!!

   sudo diskutil eraseDisk FAT32 EV3_BOOT MBRFormat /dev/disk1

   carefully check which disk number corresponds to the card and unmount

   it using commands something like the following

   diskutil unmountDisk /dev/disk1

   TRIPLE CHECK that the disk number is correct before running this!

   if you have an external drive, for example, it may be rdisk2!!!

   sudo dd if=~/Downloads/ev3-ev3dev-jessie-2015-12-30.img of=/dev/rdisk1 bs=4m

3. Eject card, insert into EV3 and power on using centre button

Connect the EV3

Set up networking over the micro-USB cable, following http://www.ev3dev.org/docs/tutorials/connecting-to-the-internet-via-usb/?tabs-0=mac-os-x

4. Wait for lights to go green and plug the micro-USB cable into the EV3 and the USB into your Mac and go to the Network in Preferences

   (+) Add the EV3+ev3dev Interface and give it the Service Name ev3dev [OK]

5. Now enable Internet Sharing for the EV3+ev3dev interface and [Start] as described in step (4) of the ev3dev Mac instructions

   You may not have to do this every time, as your Mac will remember if you use the same USB port.

6. Now configure the EV3's connection manager

   Wireless and Networks -> All Network Connections -> Wired -> Connect -> Connect automatically [*]

7. If the robot does not show its State as Online, then you may need to reboot your Mac. It appears that internet sharing in OS X can be very flakey and sometimes bootp or the DNS service don't come up or are not accessible (see http://apple.stackexchange.com/a/126229 for more info).

   Later versions of Mac OS X may also have trouble here. See ev3dev/ev3dev#471 for workarounds.

8. Check the IP address shown in the top-left of the brickman UI and then, in a Terminal window on the Mac

   ssh robot@ev3dev.local password: maker sudo reboot

   (Press <ENTER>, ~ then . to close the ssh session.)

   You need to do this to add the remote host's key to your known_hosts file and for the system to spot that the logical volume has been extended.

Note that if you see WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! it's probably because you've previously ssh'd into a different SD card image at the same IP address. Delete the line from your ~/.ssh/known_hosts file as it suggests.

Install Ansible

Install ansible on your desktop machine using http://docs.ansible.com/intro_installation.html#latest-releases-via-pip

1. Install/Update Pip (Globally)

   curl -OL https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py sudo python ez_setup.py

   curl -OL https://raw.github.com/pypa/pip/master/contrib/get-pip.py sudo python get-pip.py

2. Install Ansible

   sudo pip install ansible

3. Install sshpass

   curl http://downloads.sourceforge.net/project/sshpass/sshpass/1.05/sshpass-1.05.tar.gz -Lo sshpass.tar.gz tar xzf sshpass.tar.gz && cd sshpass-1.05 ./configure && make sudo make install cd .. && rm -fr sshpass*

These are one off steps, and if you have done them before you won't need to repeat them.

Setup Access Point

Configure and run the ansible script to set up your ev3 as an access point.

1. Edit the SSID and password vars in the ev3dev.yml file

2. Run

   ansible-playbook -i hosts ev3dev.yml

Note that if you see SSH encountered an unknown error during the connection. it's probably because you've previously ssh'd into a different SD card image at the same IP address. Run with -vvvv, as it suggests, to check and then delete that line from your ~/.ssh/known_hosts file.

If you need to modify the wifi SSID, password, country or channel after install then edit the hostapd configuration and restart it

vi /etc/hostapd/hostapd.conf
service hostapd restart

Wireless Adaptors

sudo vi /etc/udev/rules.d/70-persistent-net.rules wlan1 wlan0