Thank you PaulS and UKHeliBob
Yes I know what's a protocole but When I have posted this question I not have the informations of what I have to send !
Now I have them and it doesn't help me more...
My question is : How I can send the informations ! and not, What informations I have to send !
I use just MySerial.write() and I send the bytes one by one...
I don't know if it's correct...
I have to send informations like a start data (0xAC) and informations like motor power (-1000/0/1000)...
All I have to send as to be in hexadeciamel ?
And after I have to make the CRC8 Maxim Checksum with the data for this part I think I am ok.
Thank you