I have downloaded https://www.nxp.com/docs/en/application-note-software/AN12218SW.zip and it works successfully. There is one issue. Bootloader interface sends SREC line data at least 50ms intervals. It is huge duration for big SREC files. For instance, sending 200KB SREC file takes more than 4 min. Can you share source code of Bootloader Interface or is there faster version of it?