Saturday, 18 October 2014

Super Cheap Cruising Chartplotter and Media Player

Hi everyone,
This week we became real cruisers - we installed a TV on Zen Again!  The TV was a gift from Alain from sv CG, who I helped with his VHF and HF radios recently.  He had installed a bigger TV on his yacht and the old one was surplus to his requirements but a perfect fit for ours.

We don't expect to use the unit for live TV anytime soon.  Rather we will use it as a media player and cheap chartplotter.  Both functions are in combination with the Raspberry Pi computer we have also installed and which runs the Linux version of the excellent and free chartplotter OpenCPN.

TV installed on the main bulkhead
The TV is installed on the main bulkhead in the saloon and the Raspberry Pi in a partitioned area in the chart table.  A USB hub connects WiFi adaptor, GPS, 1TB disk and (when necessary) keyboard/mouse to the computer.

The Raspberry Pi "Zenny"
(shown out of its normal home on the other side of the divider)
The Raspberry Pi computer originated in the UK where it was designed as a cheap computer for use in schools.  It has been wildly successful and is widely used by hobbyists.  Millions have been sold.  They cost less than $40 each!  Google it for more info.

OpenCPN runs a little slowly on the Raspberry Pi but so far it is managing OK and receiving GPS information from the GPS puck.  Next week I intend to try connecting the Pi to our AIS via WiFi so OpenCPN can also display AIS traffic.  One nice aspect of the system is that OpenCPN alarms sound through our stereo system, even in the middle of movies or music.  Good for anchor watch!

If tests go well I'll try installing our library of GoogleEarth "charts" on the USB disk to see how OpenCPN copes with them on the Pi.  That might be a little too compute-intensive for it!

Raspberry Pi running OpenCPN
 The parts cost of the system, which provides chartplotting and media playing is:

  • Raspberry Pi => $40
  • SD Card => $10 (holds operating system, applications and OpenCPN charts on the Pi)
  • USB power cable => $20
  • 12V to 5V converter => $30
  • HDMI cable => $20
  • USB Hub => $40
  • USB WiFi => $20
  • USB GPS => $60
  • 1TB USB disk => $90 (holds multimedia, books/manuals and GoogleEarth "charts")
  • Total Parts Cost => $330 (not including TV)

I'm certainly not suggesting a system like this could replace a mainstream marine chartplotter,  It is certainly a very cheap and completely independent backup system.


  1. Hello I have OpenCPN running on a raspberry pi B+ ... unfortunately I am not getting the alarm bells for the anchor watch played through the 3.5 mm jack. I have tested the pi for sound through the jack which is working fine. I just wondered if you had any tips ?

    Many thanks


    S/V Cariad-y-Mor

    1. Hi Paul,
      Thanks for your question. Trying out the OpenCPN audio alarms on the Pi hasn't risen to the top of my to-do list yet. My situation is a little different in that I'm using HDMI output.

      I'll try to look into it over the next few weeks. One thing I noticed is that the "bells" included with OpenCPN aren't appropriate as alarms. I have downloaded a number of more strident wav files to use.
      Cheers and Merry Xmas,

    2. Hi again Paul,
      I have tested the audio output to HDMI from OpenCPN and it is working well for me.

      I haven't tried the headphone jack. May get a chance to do so in a week or so.

      By the way, there is a lot of info on how to force RPi audio to either HDMI or headphone interfaces online. I had to mess around a little to get HDMI working reliably. With that done it worked in OpenCPN immediately.

    3. Hi Mike

      I just wanted to say thank you so much for the replies, I have only just picked these up as I forgot to press the notify button!

      I did much research on the internet and got the pi up and running with the 3.5mm plug, I had not included all the necessary libraries when compiling the source code.

      I have the pi running headless running vnc server and then login to set up the anchor alarm - nmea source from a wireless connection to a vesper ais unit. I wrote a programme for it log all other nmea data every 20 mins. All this for very little power ( yet to be measured but less than the laptop).

      The only problem I have is there is an intermitant fault where the alarm state of opencpn triggers and flashes round the waypoint .... but the sound does not trigger. I cannot pin this down but I guess I could try the HDMI output to see if I can create the same problem.

      Anyway we hope to start cruising when the wind settles here in the UK .... thank you again and hope you keep posting !

      Take care Paul

      s/v Cariad-Y-Mor

    4. Hi Paul,
      Thanks for your comment. Good to hear you got the 3.5mm plug audio working. Good luck with solving the intermittent problem.
      Cheers, Mike.

  2. May I ask how you realized GPS reception? I.e. what GPS antenna did you use? Thanks!

  3. Hi madkissTM, I use a BU-353 USB/serial GPS receiver. AU$65 on eBay. I've used their S2, S3 and latest S4 versions successfully. Good kit.