if you have someting that could help me please post, otherwise forget.
PaulS has already given you the best advice there is.
You have probably misunderstood the interface specification. This is easily done and particularly likely given the inexperience you mention and the ambiguous way you describe the problem. If you check the interface specification and confirm you're right and the interface really does use an ascii encoded hex messaging format as you described, then it should be easy enough for you to demonstrate that by posting a link to or extract from the relevant spec so that we can see for certain what you need. In the absence of that I'll assume that you've just misunderstood. You don't have to prove me wrong - unless you want help solving the problem.