Add wifi to any camera

by Olivier Barais     OpenWRT   Camera   Canon  

Posted 2018.05.29 — Rennes, France

I have an old camera that makes very nice pictures (CANON EOS 400D), however it does not offer an easy way to share pictures with my smartphone. It’s not a big issue but I tend to use it less because I can’t instantly share these photos.

In this small blog post, I share a homemade solution to add this capacity to any device with a USB connection. The main idea is to connect a compact router to the network and automatically push the photos to the smartphone when it joins the wireless network. Of course, we can imagine others scenarios.

Materials required:

The value of this router (besides its price, its compactness, and its microUSB power supply) is the support of OpenWRT https://wiki.openwrt.org/toh/nexx/wt3020.

Flash the router

I was largely inspired by this work but the code is not open source and it didn’t work well with my device.

You can download last snaphots of openwrt to flash openwrt from stock firmware. download link

To install openwrt, we can follow the following manual in uploading the previously download image.

If you just want to update openwrt later, you can take this image

Prepare the router

When your router starts, it is necessary to connect it to the network via an ethernet cable (wan port of your nexx router). Wifi is disabled by default.

You can then connect via ssh and update the package list

ssh root@YOURROUTERIP
opkg update
opkg upgrade
reboot

Install luci (Router Web Configuration)

luci is a Web Interface used to manage OpenWrt.

opkg install luci

Install gphoto2

gPhoto2 is a free, redistributable, ready to use set of digital camera software applications for Unix-like systems, written by a whole team of dedicated volunteers around the world. It supports more than 2300 cameras

opkg install gphoto2

install the driver for your camera (for my device)

opkg install libgphoto2-drivers-ptp2

Install sshfs

SSHFS is a FUSE-based filesystem client for mounting remote directories over a SSH connection. We use it to mount phone FS to upload photos using gphotos.

opkg install sshfss

Install hostpad-utils

The hostapd utility is designed to be a ``daemon’’ program that runs in the background and acts as the backend component controlling the wireless connection. hostapd_cli is a text-based frontend program for interacting with hostapd. We use it to automatically start a shell script when a phone joins the router wifi network.

opkg install hostapd-utils

Reboot the rooter

reboot

Configure the Wifi

Unconnect the WAN ethernet cable from the WAN port and connect it to the LAN port.

Next connect to http://192.168.1.1 Default password is root root Change the password and create a WIFI AP from luci interface.

Prepare the phone

Connect your phone to this WIFI. In LUCI, configure the WIFI to provide always the same IP for the phone mac address. Install the [s]implesshd](https://play.google.com/store/apps/details?id=org.galexander.sshd&hl=fr) on your phone application and launch this application.

Prepare the ssh connection between the phone and the router

Next connect to the router using SSH.

ssh root@192.168.1.1

Generate ssh keys pair (used to copy photos to the phone using scp)


export KEY_DIR="/root/.ssh"

# Make directories
mkdir -p "$KEY_DIR"

# Generate an RSA key using dropbear
dropbearkey -t rsa -f "${KEY_DIR}/id_rsa"

# Output Public Key
dropbearkey -y -f "${KEY_DIR}/id_rsa" | grep "^ssh-rsa " > "${KEY_DIR}/id_rsa.pub"

# Show Public Key
cat "${KEY_DIR}/id_rsa.pub"

Copy the public key to the android phone using ssh: Copy the id_rsa.pub file to /data/data/org.galexander.sshd/files and rename this file with the name authorized_keys

Check the ssh connection between the phone and the router

Restart the simplesshd application on the phone.

Test the connection between the router and the phone

from the router, test the connection between the router and the phone. You should be able to connect without password.

ssh root@PHONEIP # Replace PHONEIP using your phone's IP visible from the luci web interface

Once this works, if your phone is rooted in the simpleshd application setup menu, for the Login Shell key, you can set the path to the command su (/xbin/su). Path to the command shell. The default Android shell is /system/bin/sh, but you may prefer to use the one that comes with busybox or whatever. If you set it to the su binary (i.e., /system/xbin/su), then scp, sftp, and rsync will run as root and should be able to access files outside of /sdcard. If the name of the shell contains “su” in it, instead of putting “-“ before argv[0] to indicate the login shell, SimpleSSHD puts “-“ as argv[1]. That is, a regular login shell would be invoked as “-sh”, but su will be invoked as “su -“.

Finalize the router configuration to automatically copy new photos on the phone.

On the router, install two scripts.

In the /usr/bin/ directory, create the copytophone.sh file with the following content. This script is invoked each time a device connects to the router. It is possible to filter on the MAC address of the device that connects with the $4 parameter in the bash script.

#!/bin/ash
connected="AP-STA-CONNECTED"
disconnected="AP-STA-DISCONNECTED"
HOME=/root

if [ $2 = $connected ]; then
        /bin/echo "$3 Connected!" >> /var/log/hostapd.log
        # Wait  that the user start simplessh after connecting to WIFI
        /bin/sleep 15
        /bin/rm -rf /root/test
        /bin/mkdir /root/test
        # Mount /root/test on  ... Change the remote folder on the phone if your phone is not rooted
        /usr/bin/sshfs -o reconnect,ssh_command="ssh -p 2222 -i /root/.ssh/id_rsa" root@192.168.2.198:/mnt/runtime/default/EBEB-FA00/DCIM/EOS /root/test
        /bin/sleep 3
        if mount | grep /root/test > /dev/null; then
          cd /root/test
          /usr/bin/gphoto2 -P --skip-existing
          cd /root
          /bin/umount /root/test
          else
		echo "could not mount ssh" >> /var/log/hostapd.log
	fi
else 
  if [ $2 = $disconnected ]; then
    echo "$3 Disconnected" >> /var/log/hostapd.log
    killall gphoto2
  else
    echo "$1.$2.$3" >> /var/log/hostapd.log
    echo "What happened now?" >> /var/log/hostapd.log
  fi
fi

Ensure that this script is executable

chmod a+x /usr/bin/copytophone.sh

In /etc/init.d, copy the done file to hostapdphoto. In this text file, in the boot() function, put the following content.

sleep 10
hostapd_cli -a  -i wlan0 /usr/bin/copytophone.sh&                             

replace START=10 by START=97. Enable this script by default when the router starts.

/etc/init.d/hostapdphoto enable

At the end to use the process, power the router with a small external battery, connect the phone to the router. Connect your phone to the WIFI. Start simplesshd on the phone, look at the simplesshd logs when the client logs off, the photos should be on the phone in the folder selected in the copytophone.sh script file.

Enjoy and specialize that for your own needs.

Comments

  • Yes, there are WIFI sd cards for a few euros but the use of gphoto allows to elaborate more complicated scenarios and support Compact Flash devices.
  • This could be used to more complex scenarii, in particular, you can use gphoto to control the camera from the phone 1, 2.