I just found out the OLS time axis shows no correct time when used with Bus Pirate hardware. The timescale is factor 4 too fast. I measured I2C-Signals in parallel with a Tektronix TDS220 scope and with Bus Pirate hardware v35 and OLS v0.9.5. BusPirate/OLS showed me 2.5 microseconds, the scope showed me 10 microseconds, which was the correct calculated time. OLS run with 4MHz sample rate. The effect was repeatable. Compared with other signal sources the scope worked correct.