I’ve been working on a board that interfaces with a Boron to take measurements and save data to an SD card. The firmware uses the SDFAT library and I’ve attached an image of the SD card section of the schematic to this post showing how the SPI port is used for the SD card. The firmware collects data from the sensors, writes to the SD card, and then delays for 0.1 second, and then does it all over again. This has worked well for a few months, but as we expand testing to the field there have been some inconsistent failures.
The system will flag an SD failure at (as yet) unpredictable times. Sometimes the failure will fix itself, sometimes the failure will persist despite cycling power or resetting the unit. We have multiple units; when the failure occurs on Board A and Boron A but does not fail on Board B and Boron B, we can swap the Borons so the failure follos the boron (Where Board B and Boron A continues to fail).
Question 1: Has anyone had issues similar to these? Could we be missing anything?
I am working remotely to troubleshoot the error on my bench and only have 1 unit. My unit does not exhibit a failure, however I attached my 4-ch scope to look at the signals, and found that while it starts OK, the clock signal becomes a ‘runt’ and while the system still seems to work, the signal is concerning. I am attaching a scope shot showing the first write to the SD card that starts out well, but then the clock delivers runt signals.
Question 2: Has anyone seen anything like this? What, if any, conclusions could be drawn from this scope shot? I have another Boron on the way to test if I have a damaged unit.
We are at the early stage of troubleshooting a problem that so far this week has decided not to show up. I would be open to any suggestions or ideas!