I-Cube LRWan, where to set the Spreading Factor (SF)

I'have imported the I-Cube LrWan (LoRa) library and end_node example into SW4ARM (Eclipse). This example is working (With SX1276MB1MAS) module.

By default it sends a LoRa packet with SF12. Where (which .h file) can I set this Spreading Factor?? to SF7 for example. I have been looking through the code for hours now.