OpenCPN plugin API : working with ais

[creekorful]

Hello everyone,
I currently work for a little compagny, and i have to made a plugin for OpenCPN.
My plugin target OpenCPN 4.2.0.
I have to send and receive NMEA3008 data from the AIS.
My plugin can read data from the AIS (using SetNMEASentence() event) but only when the trame begin with "!" and not "$" any idea why ?
By the way i don't know how to use PushNMEABuffer() function to send data to the AIS.
Is there any example of this ?
Thank in advance, and sorry for my bad english.
Creekorful