why sink hackrf one only can work with data int8

[stackprogramer]

when i want to work with hackrf one sink in simulink it returns and limit me that data type should be int8.....
why it has not option for select data like source.......
thanks

[stackprogramer]

@skoslowski
for FM transmit with Sink, that only it has data type int8.
when i used Convert block Matlab to transmit FM we can not any data on fm receiver,

but with source hackrfone we can hear FM local station. my question is int8 can proper for FM transmit? why sink hackrfone it does not support floating data.
thanks

[skoslowski]

int8 is what goes over the wire as I recall.