I have a bit of a challenge and was hoping to get some ideas.
I have a BMS board that is connected to some batteries, and part of that BMS has an MCU. There are two connectors in the design, a data connector, and the power connection. Here is a simplified diagram:
Externally I can easily detect if the data connection is missing because I am not able to communicate with the MCU. However, I'm having a harder time detecting if the power connection is plugged in because I am also providing power back to the battery under idle conditions to charge it (think of the battery as kind of a battery backup).
The data connector is used to supply the MCU with power from an external source (if there is no external connection, you don't need to talk to the MCU). I am hoping to have the MCU detect if the power connectors negative terminal (pack-) is not connected by some means of utilizing a path with the supply voltage that is coming in on the data connector (5v).
I just want to generate an output on ALERT via the MCU if the pack's power terminal is not connected.
Externally, the GND and Pack- would likely be tied together.
The BMS is based on this: http://www.ti.com/tool/TIDA-00792
If you have any high level ideas, i would greatly appreciate it!