I don’t exactly know if you can put Hydra into serial debug mode like most other Fez devices. Usually there’s a MODE pin that forces serial debug, but I can’t find reference for Hydra that talks about it. Then you connect COM1 to a USB Serial adapter of some form, connect that to the PC, and you can deploy thru that. I hope the SP is your issue, and the new one addresses it. Good luck!
Hi Brett,
I’m going forward with my tech problems !
I’ve managed to communicate with the board and to put a 4.2 firmware version, but I still have some problems to deploy the solution !
I’ve opened a new topic for that if you can take a look 
See you there maybe !
Thanks again !