NT Data Logging
A data logger can be connected to the NT bus, which allows us to record on a micro SD card a substantial amount of data for each cycle of the controller loop. It thus records the data with the maximal possible time resolution. Furthermore, the logger is quite small and can be easily mounted on-board. As a result one can get highly accurate and informative data taken in the real flight condition. This hopefully will allow use to better diagnose any troubles, such as jello or micro vibrations in the video, and find solutions to resolve them.
The data logger option also suggests many other applications. For instance, it can be used to dynamically balance the motors and propellers.
NT Logger Module
The NT logger module is connected to the NT bus, as any other NT module.
The micro SD card should be of very high speed. Unfortunately, not any card works equally well. Little experience is available so far:
- Kingston cards seem to work not well, and in some cases don't work at all
- the firmware author is using a SanDisk Extreme SDHC 16GB UHS-I Class 10 U3, with very good results
The micro SD card must be formatted with FAT32.
NTLoggerTool
For analyzing the recorded data, the NTLoggerTool is available, providing tools such as FFT, and others. It also allows us to convert the data into other formats, most notably into .cfl files. The .cfl files are suitable for the program BlackboxExplorer for STorM32, which is a decendant of CleanFlight's powerful BlackboxExplorer. The NTLoggerTool also allows us to record directly the data on the NT bus usiang a USB-TTL adapter, which enables many work-bench tests and procedures.
The NTLoggerTool is steadily advancing with fast pace, and any manual would be quickly outdated. For a discussion it is best to join the STorM32 NT thread at rcgroups.
The NTLoggerTool is open source (GPL3). Anyone is highly welcome to contribute to it.