I know it's tooooo late, but this may help the others .
first , your calculations mix floating points with integers , you have to solve this.
but this is not the problem .
by checking github ref of this lib , i guess radio.write() function should called on string ! check attachments
so i guess you need to write a function to convert your variable to string , before you radio it
ex:
char* convert_int16_to_str(int16_t i) {
sprintf(tmp_str, "%6d", i);
return tmp_str;
}
that worked for me .
