Updating old home wiring
Next steps were to enable and connect the camera, and to install ffmpeg, which is what I use to stream to You Tube.
So they don’t provide tracking throughout a flight, which is a problem as then you don’t know where the payload is until it lands. There are 2 problems here – one is that GSM coverage isn’t 100%, and the other is that the popular GSM trackers don’t seem to like high altitudes.I don’t know if they get confused, or they don’t like the cold, but I’ve tried these things several times and only had one work once.A GSM/GPS tracker that actually works would be useful though, as a backup to a main tracker.This requires the 5V and GND lines on the GPIO pins, plus the composite video output pin, to be wired to their counterparts in the monitor.Once I’d used the correct video pin this worked without issue!So that plus a Pi Zero and suitable power supply would make a fairly small backup tracker, and maybe even one that works. It seemed attractive to use GPRS to provide internet access (via PPP), but that would lock out the single serial port thus making GPS unavailable.
The device supports GSM (calls, texts) and GPRS (2G, i.e. So I decided to just send SMS from the device instead, using a script that gets the GPS position, then builds and sends an SMS containing that position.
So my test script requests and parses the GPS position, then formulates a text message and ends it to my mobile phone: It would also be useful to have the balloon position automatically uploaded to the live map, so I decided to have the device send a second SMS but this time to a gateway based at home.
This gateway is another Pi with a USB 3G modem attached.
I wrote this in Python using the Py GSM library, which makes things very easy (generally no need to mess around with AT commands).
Py GSM doesn’t know about the SIM868 GPS functions however, but it was simple to add those.
At present I’m not recording the video, so I need to do that using rotating file names, over-writing old files before the SD card fills up, and recording at a high resolution but streaming at a lower resolution.