I’ll start with a TLDR: how do you test that a module will work with a terrible power supply!
Now for the long version: I made a simple digital module and it worked fine when it was the only module connected to the power supply. After a bit of initial testing I put it in a case with some other modules. This system is not very good - it has a pretty poor power supply and some of those horrible flying bus cable things.
At this point, my module wouldn’t start unless I powered everything on, then turned it off for a second and turned it on again. I checked with the oscilloscope and it was due to the power supply taking a long time to ramp up.
I came up with several ideas to fix this problem, but one of them needed some changes to the firmware / fuses and the Arduino core I was using didn’t seem to support them, so I ported my code from Arduino to pure C++. Before implementing the changes I tried to reproduce them again, but now it (seemingly as if by magic) just works. In fact sometimes a different module fails to start now!
So I’m not looking for a solution to the power supply problem right now. I can see in the Mutable Instruments modules there is sometimes an LDO for the MCU and another 3.3v regulator for the analogue stuff (if needed). I will try this and some other things, but before I try that I need to reproduce the problem!
This is my question: how to I reliably replicate the initial behaviour? Is it best to try to attach some kind of load to the power supply? Do I use a lab power supply and slowly ramp up the voltage to 12v manually (I highly doubt this is the answer!)? Do I need to make a special power supply where I can control the ramp up speed?
I have no idea why switching from Arduino to native C++ caused it to need less power on startup!