@glv I think I found where the problem comes from (on my side) :
I did some experiment and if have no problem sending any buffer up to 63 bytes (including ‘\n’) like :
char pcOutBuffer[] = "this is an example of a 62 characters payload which works fine";
However when reaching 64 bytes, no serialEvent are triggered on Processing side and above 64 bytes then my problem appears
Now I think can implement a proper workaround but I’m still unsure about the real explanation.
What do you think of that @glv ?