The Flat Field Correction (FFC) requires the use of the raw video output from the Tau2 to calculate per-pixel offset corrections. All commands must be blocked during its operation for the offset calculations to be computed properly.
Additionally, the FFC is known as an “asynchronous” or “non-blocking” command. Asynchronous commands are those which the core replies to the command before its execution is complete. Therefore, users who periodically query the Tau2 serial port for information should monitor the “FFC in progress” status flag using the READ_SENSOR command (0x20) and halt all commands sent to the Tau2 while the FFC is occurring. Users that operate the Tau2 in manual mode can also monitor the READ_SENSOR command after the DO_FFC (0x0C) command has been commanded. The nominal FFC operation takes ~0.4 seconds and the long FFC operation takes ~0.5 seconds.
This duration should increase if the user has increased the number of frames integrated from the default value using the FFC_MODE_SELECT (0x0B).