Circuit including a first port to couple to a first device; a second port to couple to a second device; a first channel having an input coupled to first port and an output coupled to second port, the first channel to re-drive a signal and output re-driven signal; a second channel having an input coupled to second port and an output coupled to first port, the second channel to re-drive a signal and output re-driven signal; and a controller to: enable first channel and disable second channel responsive to detecting a signal edge at first port; enable second channel and disable first channel responsive to detecting a signal edge at second port; sample impedance at first port if signal received at first port is de-asserted while first channel is enabled; and sample impedance at second port if signal received at second port is de-asserted while second channel is enabled.