For some test equipment I have an LVDS line running at 100 Mbps. I would like to make an Arduino Due (because I use this for other monitoring in the test) detect activity on the LVDS line.
Using a (bad, slow) scope I can see that the voltage swings at one of the differential inputs on the LVDS receiver is ~100 mV. It is probably higher (it should be according to the LVDS spec) but my scope or probe is probably just not fast enough to catch it.
Can someone suggest a small circuit I can put on either one or both of the differential inputs in order to monitor the activity? It does not need to be production quality, and it's ok if some tuning is required, as it is only for test purposes.
I was thinking about something along the lines of an capacitor (to block common mode DC) followed by a voltage biased high-speed Schottky diode to rectify the signal onto a small capactor from where I could read the voltage using the Arduino. But honestly I have no idea if this would even work…
Best Answer
Your idea is good, but I think that you will have better luck if you put a proper transciever at the end.
A toggling signal will cause a DC voltage at the output. If the recovery time of the 1N4148's is too slow, use Schottky diodes instead.
simulate this circuit – Schematic created using CircuitLab