SD card logging
rusEfi supports SD card logging. SD has to be formatted FAT16 or FAT32, up to 32Gb cards are known to work.
logs are being written at about 2 megabytes per hour, so the oldest 128Mb card would be enough for a track day and a newer 32Gb card would hold the logs for a year.
In rusEfi console sdinfo command could be used to query logging state.