You can download xxtea for your preferred language from here:

https://github.com/xxtea

Then write small program that reads encrypted file then skip first 7 bytes and call xxtea_decrypt. But when I wrote program that does this - function failed. I tried different languages thinking that there could be bug in one particular implementation but function still failing. This was my second big disappointment. For some time, I didn’t know what to do. In desperation I started looking at decrypt function and accidentally I found this:

0x96cc28fc:  movw    r1, #55894      ; 0xda56
0x96cc2900:  movw    r2, #31161      ; 0x79b9
0x96cc2904:  movt    r1, #46412      ; 0xb54c
0x96cc2908:  movt    r2, #40503      ; 0x9e37