Doohh ... User error - 1PPS wasn't enabled on the GPS. The OPIO Kernel works fine w. 1-PPS $ sudo ppstest /dev/pps0 trying PPS source "/dev/pps0" found PPS source "/dev/pps0" ok, found 1 source(s), now start fetching data... source 0 - assert 1524154630.697340907, sequence: 6793 - clear 0.000000000, sequence: 0 source 0 - assert 1524154631.697261112, sequence: 6794 - clear 0.000000000, sequence: 0 source 0 - assert 1524154632.697166525, sequence: 6795 - clear 0.000000000, sequence: