Jun 3 2013

ATV generator

For Amateur Television I was looking for a simple and standalone video generator that could do the following:

  • Show predefined pictures in graphic format ( .jpg )
  • Play movies (in mpeg format)
  • Play sound (MP3 or WAV format)
  • Simple to use
  • Network capable (uploading pictures)
  • PAL output
SAM_0313

Front view of RPI-ATV

 

For all of above items I decided to use the RaspBerryPi because of its simplicity and price, programming is done using python. Script can be improved a lot, I’m not a professional programmer and this is the first time I’ve used python. If you decide to change/rewrite or improve my script, please send me an email : pa3bwe at amsat dot org

SAM_0302 Wire added to the backside of the board because I didn’t want to add extra connecters internally.

SAM_0303

Raspberry PI board mounted inside a aluminum box

SAM_0308

Inside view towards front panel

 

SAM_0314

Front panel view of 1st revision

SAM_0450

Front panel detail of 2nd revision, now includes toggle switch to scroll to available pictures without using keyboard.

SAM_0315

Backside of generator, has only DC input connector

SAM_0321  SAM_0324  SAM_0325

Some testpictures which are stored internally.

SAM_0323

Semi static picture: colors will change randomly!

Software used/installed :

  • Install latest software for RaspBerry PI (check RPI website)
  • Install python-pygame to create graphics
  • Install samba for networking with Windows
  • Install RPi-GPIO for external switches to scroll through images (2 ground closures on pin 24 and 26)
  • Python (comes with unix distribution)
  • Script to display pictures ( atv.py atv2.py atv3.py), install in /home/pi/atv
  • Copy images in /home/pi/atv/images using imageX.jpg format (image1.jpg to image25.jpg)
  • Copy sound file in /home/pi/atv/sounds (default soundfile is sound.wav)
  • Keys for ATV script :
    • I: toggle internal generated picture (default on)
    • R: toggle random picture mode (default off)
    • S: toggle sound on/off (default on)
    • T: toggle floating text on display (default off)
    • Q or ESC to end program
    • F1-F12 selects user-defined images (image1.jpg to image12.jpg)
  • Adjust /boot/config.txt to force RCA output to PAL or NTSC an optional change overscan parameters

Hints:

  • Use pictures scaled to 768 x 576 (tnx to Dick, G4BBH)
  • Editing of software is done over SSH from a Windows PC, makes live much easier…
  • Start script with root privileges (sudo python atv3.py) to overcome rights with GPIO library

Things to change/add to the python script:

  • Add sound output (added in atv2.py)
  • Add toggle switches to scroll through pictures the simple way (added in atv3.py)
  • Add function to play mpeg movies
  • Add menu to display choices
  • Rewrite the software, can be much better/nicer (I’m not a programmer but a simple hacker….)

Things needed:

  • Time to do all this ….

By • electronics, ham • • Tags: ,