NXP programs every NHS31xx IC with firmware which acts as a second stage bootloader. It provides the functionality to program the final firmware in the IC via the NFC interface, allowing late-programming outside a production environment.
This APP implements the communication protocol to interact with this initial firmware on the NHS31xx ICs.
You can select which final firmware application must be loaded: the required file can be downloaded after scanning a QR-code or can be selected in a file explorer. This file will be fragmented into chunks and sent one by one using the NDEF protocol to the NHS31xx IC. When download is finished, the second stage bootloader is no longer available: the IC is reset and the new application executed.