16. Flight Data Recording¶
Each flight computer logs data at 100 samples per second during ascent and 10 samples per second during descent, except for TeleMini v1.0, which records ascent at 10 samples per second and descent at 1 sample per second. Data are logged to an on-board flash memory part, which can be partitioned into several equal-sized blocks, one for each flight.
| Device | Bytes per Sample | Total Storage | Minutes at Full Rate |
|---|---|---|---|
| TeleMetrum v1.0 | 8 | 1MB | 20 |
| TeleMetrum v1.1 v1.2 | 8 | 2MB | 40 |
| TeleMetrum v2.0 | 16 | 8MB | 80 |
| TeleMini v1.0 | 2 | 5kB | 4 |
| EasyMini | 16 | 1MB | 10 |
| TeleMega | 32 | 8MB | 40 |
| EasyMega | 32 | 8MB | 40 |
The on-board flash is partitioned into separate flight logs, each of a fixed maximum size. Increase the maximum size of each log and you reduce the number of flights that can be stored. Decrease the size and you can store more flights.
Configuration data is also stored in the flash memory on TeleMetrum v1.x, TeleMini and EasyMini. This consumes 64kB of flash space. This configuration space is not available for storing flight log data.
TeleMetrum v2.0, TeleMega and EasyMega store configuration data in a bit of eeprom available within the processor chip, leaving that space available in flash for more flight data.
To compute the amount of space needed for a single flight, you can multiply the expected ascent time (in seconds) by 100 times bytes-per-sample, multiply the expected descent time (in seconds) by 10 times the bytes per sample and add the two together. That will slightly under-estimate the storage (in bytes) needed for the flight. For instance, a TeleMetrum v2.0 flight spending 20 seconds in ascent and 150 seconds in descent will take about (20 * 1600) + (150 * 160) = 56000 bytes of storage. You could store dozens of these flights in the on-board flash.
The default size allows for several flights on each flight computer, except for TeleMini v1.0, which only holds data for a single flight. You can adjust the size.
Altus Metrum flight computers will not overwrite existing flight data, so be sure to download flight data and erase it from the flight computer before it fills up. The flight computer will still successfully control the flight even if it cannot log data, so the only thing you will lose is the data.
