Originally posted by mcgregni But it does beg the question about how Metz, Sigma and Tumax/Bolt etc manage it. Is it by agreement and co-operation or just through testing and development .....
Hook up an oscilloscope to the hotshoe, use the camera, watch what happens. Then make the flash do the right thing at the right time. Release the product...hope that you didn't miss anything. Find out you missed something when customers start complaining, then change your firmware and release (in the case of Metz by user update, others by a new version of the product). Wait until Pentax starts using part of the protocol that wasn't previously active (like in a new body) and update again when you find out what it is. As long as you invent your own way to react to the output of the hotshoe, you're doing nothing wrong.
To infringe the patent, you could instead hack the internal chips to give up their hex code and copy and paste to your own chips. If you were a no-name Chinese company this is fairly standard practice in some fields, but the likes of Metz or Sigma wouldn't dare...probably.
If you lack either the time, money, energy, expertise, or (most likely in Petax's case) the return on investment to make it worthwhile, you make up an excuse for your disappointed customers...mention patents or something and most people will not bother you any further.