Hi Thomas,
to correctly sum up an array of U8 you have to convert them to a "bigger" datatype. ANDing with $FF just keeps the low byte before converting the result back to U8 needed for your checksum...
Edit: You know you can edit posts instead of adding another post just a minute later?
Best regards,
GerdW
using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019