Private LoRa Protocol Source code for LT-22222-L. The LT22222-L_PingPong_v1.0.hex is pre-built firmware which can be and upgrade to LT-22222-L directly, upgrade method is the same as per instruction in LT-22222-L.
http://wiki.dragino.com/xwiki/bin/view/Main/%20Point%20to%20Point%20Communication%20of%20LT-22222-L/
See http://wiki.dragino.com/xwiki/bin/view/Main/Firmware%20Compile%20Instruction%20--%20STM32/