Now it's nearly done
I took KY_HARD.DRV from S1 Mp3 3.5.37 Wilson Co. Ltd. Firmware and put it instead of the local one. But I had to remap some keys also, and now it works fine.
Last trouble is Volume button - I didn't find what code is answering for it. So if you know, please, tell me its code.
Also, if you need such a firmware, I can send you it by email.