To do this I needed:<\/p>\n My car has a MiFi device and the Pi connects to that by WiFi.<\/p>\n Monitor<\/strong><\/p>\n There are many tiny monitors available that are sold on ebay and elsewhere as “rear view screens” for cars. \u00a0They run on 12V at low power, and have a composite video input which the Pi can drive directly. \u00a0They usally have 2 such inputs so you could also use them with a rear-view camera for example. \u00a0I bought a 4.3″ folding model which is slightly better resolution than the smaller ones:<\/p>\n Just supply 12V power (only about 150mA needed), connect the Pi and power that up (for a car just use a good<\/strong> car Micro USB adapter). \u00a0You may need to adjust the “overscan” settings to centre and size the picture correctly.<\/p>\n GPS<\/strong><\/p>\n This is needed so the Pi knows where it is, so it can upload the car position and so it can calculate where the balloon is relative to the car. \u00a0I used a UBlox module but for this application any GPS receiver with a “TTL Level” serial output will do. \u00a0Connect to the GND, 3.3V and serial Rx pins on the GPIO connector.<\/p>\n Camera<\/strong><\/p>\n The Pi Camera is the obvious choice, as it is cheap, good quality and has very very low CPU overhead.<\/p>\n <\/p>\n Software<\/strong><\/p>\n I split the task into several programs which share a block of memory that contains the GPS and balloon data. \u00a0The programs are:<\/p>\n Both batc and chase.c read switches connected to the GPIO ports to enable\/disable the batc streaming and chase car upload.<\/p>\n batc Streaming<\/strong><\/p>\n Streaming works really well with the Pi camera – much smoother than when I did this before using a webcam.<\/p>\n <\/p>\n I can stop and start the streaming using a switch. \u00a0This is tested using a small shell script which starts or kills ffmpeg and raspivid accordingly. \u00a0The status of the switch is shown on the LCD.<\/p>\n Chase Car Upload<\/strong><\/p>\n This is pretty easy to do, using the GPS data read elsewhere. \u00a0The result is that the car position is always visible on spacenear.us (assuming an internet connection):<\/p>\n![\"carpi\"](\"http:\/\/www.daveakerman.com\/wp-content\/uploads\/2013\/10\/carpi.jpg\")
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