A couple of examples of hard problems might be the best approach. - loss of ground A vehicle OBD connector can at times, loose its GND pin. There are actually

A couple of examples of hard problems might be the best approach. - loss of ground A vehicle OBD connector can at times, loose its GND pin. There are actually two GND pins - chassis and electrical that can sometimes disagree. Its possible for one of either of them to either (a) loose connectivity (b) bias towards the signal level or head towards a negative signal level (-2v was our typical observation). To prevent an OBD protocol pin from dumping current down the channel, a complex HW/SW solution is needed to monitor and react quickly to prevent downstream ECUs from being fried. - security We built a custom debug tool based on CM-DAP (ARM debugger technology) that included OOB security paths to unlock a device for re-flashing / debugging. I think we made 500-1k of these in total for manufacturing/RMA/logistic purposes. This was super fun to work on :)