The logger contains its own processor and USB connector but only needs to be flashed once. It is flashed just like an airframe: clean, build, plug USB to the rear connection, power up and click upload. The configuration can be found as LOGGER in the example file conf/conf.xml.sumo
You might need to reflash the logger in case you accidently overwrite it with an airframe configuration. That should not happen again as the USB connectors are clearly separated and not next to each other as they used to be.
The logger will automatically start writing the autopilots (and Aeroprobe) data to the SD card. To stop the logging there is no longer a mechanical button. It will be stopped through the gcs. Go to the gcs middle panel -> Settings -> Modules. There is an entry "log_sd_spi". The number next to it shows if the logger is running or not, click on the number to update or if there is N/A. It will be "1"/"START" if the logger runs or "0"/"STOP" if stopped. Check the "STOP" radio button and press the green commit button to stop the logger, see attached picture. Once the logger is stopped it can for now not be restarted through the gcs. The aircraft has to be power-cycled.
To download and convert the data you need to stop the logger (now through the gcs), connect the logger USB connector to the laptop while aircraft power is still on and wait for the mass storage device to appear.
The telemetry is written in the Paparazzi .tlm format that adds a timestamp to each message. The logger starts with 00000000.TLM in the main folder of the SD and increases the number with each log session. Already used numbers will not be overwritten.
Make sure environment variables are set before running pprz programs from the commandline
me@home:~$ export PAPARAZZI_HOME=~/paparazzi me@home:~$ export PAPARAZZI_SRC=~/paparazzi
The data is converted back to the Paparazzi .log and .data format using sd2log
me@home:~/media/usbstick$ ~/paparazzi/sw/logalizer/sd2log 00000002.TLM Renaming produced file ... 09_08_13__20_55_03_SD.data file produced 09_08_13__20_55_03_SD.log file produced 09_08_13__20_55_03_SD.tlm file saved
It creates timestamps from the .tlm and changes the filename to the take-off time if a GPS message with correct time was available in the file or the current local PC time if no GPS was available. The .log file will be re-created either from the current configuration (if still in existence) or the MD5-labeled files that are stored in var/conf each time you build an aircraft. All resulting files are stored in var/logs with an _SD extension.
See data logger for more details.