I am trying to use my APM 2.5 as a data logger. Ideally I would like to get about 3hrs, storing GPS data at 10hz, and IMU and attitude data at 50hz. In an initial test it looks like the onboard 16mb memory lasts about 30min. Is 30min roughly what should be expected logging this data?
I see two paths to increasing the log duration. First, is it possible to add additional memory to the APM 2.5 in order to increase the log capacity? Perhaps add an external SD card?
Second, are there possibly a more efficient ways to store the log file using the 16mb of dataflash already there? I noticed that the log file exported by the mission planner from my 30 minute test was a 6.7mb ascii file. So, is there other information being written to the onboard memory that uses up the other 9.3mb? If so, can this data be left out, or at least limited in size? Is the log file stored in ascii or binary in the data flash? If the exported ascii file is 6.7mb, is seems like a binary file should be much smaller.
A few other questions about how the log works. When looking at the logs in the mission planner, it says which pages a log starts and ends at. What exactly is a page? And how many pages can be stored on the internal memory?
When plugging my APM in to retrieve the data files the board appears to start logging again as soon as it is powered on, overwritting data if the memory is full. This stops once I change to CLI mode. Is there any way to prevent this initial overwriting if there is data that I want to protect? It looks like there used to be a switch for this, but that is was removed after the APM 1.0.
Analyzing the .log file, there appear to be many lines that are only partially written. Or perhaps that there was a concurrency issue and the GPS and RAW data tried to write to the log at the same time? Is this normal? For example part of my log file is below:
GPS: 359266400, 0, 0, 0.0000000, 0.0000000, 0, -27.3700, 259.2100, 0.0000, 0.0000
ATT: -6, 5,RAW:-0.00,-0.00,0.00,0.02,00,0.03,0.01,-9.79,
ATT: -6, 5, 18588
I am very new to this, So thanks for the help. And sorry in advance if any of these questions are overly obvious. So far the hardware and software looks great and very powerful.