Pictureframe of Things

internet-accessible (and -updateable) e-paper display, powered by Onion Omega, and mounted in a classy frame

parts required

• Onion Omega -- Primary IoT controller device
• Mini Dock -- Power and USB connectivity
• Waveshare 4.3" e-Paper display -- Fancy e-Paper display with serial control interface
• CP2102 USB to TTL serial adapter -- USB serial port to control the display
• A classy picture frame, plastic foam, and tape for mounting -- Because being classy matters

additional requirements

If you want to expose your Pictureframe-of-Things to the public internet, you'll need a server somewhere that can proxy requests back to the Onion Omega. In my case, my Onion Omega makes an ssh tunnel to a dedicated server, which uses name-based virtual hosting to proxy all requests for www.pictureframeofthings.com back to the Onion Omega's lighttpd server.

If you don't care about exposing it to the internet, it will still be available for updates on your LAN, as well as over the Onion Omega's built in wifi access point.

noteable gotcha's

• truncated serial output issues

  For some reason that I could not discover despite spending many hours trying, my Onion Omega seems to be ignoring O_SYNC and fsync(int) when writing to /dev/ttyUSB0, but apparently only when the standard input to the display update tool was a pipe and not a tty nor a pty. So, when the tool tried to close its filehandle for /dev/ttyUSB0, the serial output buffers were getting flushed (rather than drained) no matter what I tried.

  The solution to this was to just add cat /dev/ttyUSB0 > /dev/null & to /etc/rc.local, which forces the USB serial port to remain open at all times, and thus avoiding the data truncation issue.

• gcc via opkg doesn't fit on an Onion Omega

  This issue wasn't too terribly hard to get around. Since I have two Onion Omegas, I used one of them as my "build machine". In that one I plugged in a 12GB flash drive formatted ext4, copied /usr to the drive, then mounted with --bind on top of /usr. This resulted in there being plenty of space on /usr for gcc.

mount /dev/sda1 /flash cp -Rp /usr /flash mount --bind /flash/usr /usr

After those commands, I was able to install `gcc` using
`opkg install gcc --force-space`.