Got the GPS module connected to the Arduino flight computer today. Easy to connect except that since it’s an olde module it needs more power than the Arduino’s 3.3V output can manage (130mA needed; 75ma available). Connected to a software UART to make the debugging easier (PC connects to the hardware UART).
All connected, I could see the GPS data coming through but the position values were all zeroes. This is normal at first until the GPS module locks onto enough satellites and downloads enough data to decode them. So I waited. And waited. Even after 30 minutes no position data came through. Checking the GPS manual I saw that it only sends power to the antenna if I connect power to a specific pin for that purpose. So out with the soldering iron again. Power back to the GPS and, within a few seconds, position data! It took a couple of minutes for the position to be accurate, but that’s normal. One more thing on the checklist then!
I also did some tests to see how long the camcorder can run on Lithium cells. As per an earlier post these provide too high a voltage, so I connected through a schottkydiode to drop the voltage just a little. Doing this also makes it easy to double up on batteries, so with 4 AA Lithium cells connected in this way I timed the camcorder at about 3 hours 34 minutes. I can get more by shorting diodes out when the battery voltage has lowered a little. One for the flight computer to monitor and control.