prog_uchar should only be used for variables that are going to be stored in PROGMEM (and it's depricated in avr-libc 1.8.0, so you should probably get rid of it completely). Specifically, testdata3 should be unsigned char, not prog_uchar
prog_uchar should only be used for variables that are going to be stored in PROGMEM (and it's depricated in avr-libc 1.8.0, so you should probably get rid of it completely). Specifically, testdata3 should be unsigned char, not prog_uchar