Arduino UNO
IDE 1.8.19

fastShiftIn_test.ino
0.2.3

 8 bits HIGH


Performance - time in us : read()
FastShiftIn1: 20.42
FastShiftIn2: 39.72
       Delta: 19.30


Performance - time in us : readLSBFIRST()
FastShiftIn1: 19.80
FastShiftIn2: 38.84
       Delta: 19.04


Performance - time in us : readMSBFIRST()
FastShiftIn1: 19.80
FastShiftIn2: 38.84
       Delta: 19.04


Performance - time in us : reference shiftIn()
Standard shiftIn1: 108.61
Standard shiftIn2: 216.43
            Delta: 107.82

done...