It's pretty interesting to dive into the situation of recovering from unexpected reboots. Our usual lab setup consists of three parts:
- The PC running our Generic EGSE software: a user interface for powering, controlling and reading out a sensor
- The so-called Controller board, an off-the-shelf board from Pender Electronics, running our embedded software
- A project-specific electronics board with one or more DACs and/or ADCs to bias and control the sensor equipment, hereafter called the biasing board.
Any of these could suffer unexpected power loss and subsequent power restore. The basic question is: what do we handle in the way of recovery?
For lots of things, it's necessary to maintain status. An example is the following: you are a scientist and use the above setup to set up and test your sensor. You leave the lab but then the PC unexpectedly reboots because a system administrator mistakenly remotely rebooted the PC.
When the EGSE software automatically starts again, should it attempt to initialize the biasing board? Probably not -- you may be running a test and the sensor settings should not be changed.
But then again, there is the situation of an expected power-up. You want to differentiate between the two, if you want your electronics to always be initialized upon normal startup.
Now there's complexity: both the EGSE and the Controller board will have to maintain state. Any discrepancies will have to be resolved between the two. In the end, it might be much simpler to just say that we do not support automatic initialization when the Controller board comes online.
Choices, choices...