I want to make android app that able to upload .hex file to arduino via bluetooth. There is a arduino IDE for windows who compiled program and creates .hex file and able to upload to arduino via USB and bluetooth. There is app call arduino commander on play store which can able upload .hex file via OTG. And there another app called Bluino Loader on play store which can able to upload .hex file via bluetooth. I heard about STK 500 v1 protocol is used to upload .hex file to arduino .I get that protocol from github , but that is not working . So please give me any solution .