Raspberry pi sstv

sending photo's via a raspberry pi on the 2m band


Edsard Boelen, 16-july-2014
PA3BYA has won the maker contest with his raspberry pi sstv project. It uses pi-noir to capture images. Then it converts them to sstv stills, and after that it uses PiFM to send it on the 144MHz band.
It is easy to build and the result is nice. This week the new raspberry pi model has become available, I will built it on that.

get the raspberry pi model B+

At the day of the announcement, I ordered one, it is the same price as the old model: $35. The next day it was delivered.

A sdcard with raspbian is needed for it to operate, it can be bought pre-installed, or install one yourself.

converting images to sstv sound files


KI4MCW has created a c implmentation which converts images to sstv files.
The source code can be found here or at github. Al the build tools are already installed with raspbian. Just compile it with:
$ sudo apt-get install libgd2-xpm-dev libmagic-dev
$ gcc -lgd -lmagic -o pisstv pisstv.c
I have created my own test image of 320x320.


it can be converted to a sound (.wav) file with the following command:
$ ./pisstv test-image.png 22050

sending at 144.5 MHz

The raspberry pi has a very nice pwm directly available on I/O pin number 4. No software or hardware required to control it. That is one of the reasons why thr raspberry pi is so popular.
The imperial college from London has built a Fm radio transmitter using pin 4 of the raspberry.
get the code here and compile it with:
$ g++ -O3 -o pifm pifm_sstv.c

run the program with:
$ ./pifm test-image.png.wav
If you have a receiver nearby, you can hear the distinct sstv sounds clearly at 144.5MHz.

receiving the image

I used slowrx to receive and convert the image. It can be compiled on another raspberry pi, but as it lacks a sound recording input, I just used a normal machine.
Get the source package here. For compiling, some libraries like gtk3-devel and libasound-dev were needed, but no further difficulties for compiling, just run the following command:
$ make
. Everyting was set after connecting the data output from my yaesu 8900r tranceiver to the mic input of my computer,
slowrx will automaticaly start converting if it receives the start sounds of a sstv transmission.
after 2 minutes it looked as follows:


here is a small movie of the reception of the data.