Automotive GMSL cameras are one of the few camera families that still get a true end-of-line test on a production line, and one gate there deserves more attention than it usually gets: link margin.
A streaming picture only proves the link works right now. Margin tells you how much safety distance is left. The link is a coax run from the serializer (camera side) to the deserializer (capture side), and cable aging, a poorly seated connector, or a damaged equalizer slowly eats signal quality — invisible in the image until the day the link dies on the road.
The measurement follows the GMSL2 channel spec: start at the serializer's default transmit amplitude, step it down in 10 mV increments, dwell at each step and watch for errors, on the forward channel (video) and the reverse channel (control) separately. The number of clean steps before the first error is the remaining headroom. A healthy module keeps running many steps below nominal; a worn cable throws errors early — while the picture still looks perfect.
Three discipline points that make it work as a production gate:
– A written floor per module variant, under version control. Changing the floor is changing the spec.
– Every unit, no sampling. The camera you skip is exactly the one with a perfect picture and no margin left.
– Every reading filed under the serial number, so a field return becomes a query instead of an archaeology project.
TL;DR: a perfect picture proves the link works today; margin predicts whether it survives the vehicle. Step the amplitude down, count clean steps, judge against a written floor, file everything by serial number.
Disclosure: I work on embedded vision at EyeCloud AI — happy to answer follow-ups.
