this is the response from Nissin regarding their flashes.
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The slave system of Di622 is optical slave system and its sensor circuit
is designed so that it responds to the pre-flash system flash unit.
As explained in its instruction manual, Di622 is triggered against the
master flash, which must be Nissin Di622, Camera's built-in flash or
camera manufacturers original flash at its TTL flash photography.
Di622 does not work for, manual flash system, camera's
transmitter(commander), studio flash system and radio trigger system.
The slave system built-in Di466 works all optical flash trigger system,
but not supports transmitter(commander) or radio trigger system.
Since the trigger system is electrically designed but not by program
setting, it can not be improved by software.