When I do a software-directed shutdown of my Raspberry Pi, the activity LED blinks at a fixed rate for a while, then stops.
Is it safe to remove power when it is doing this final blink pattern, or is it in fact still writing to the SD card during that time?
Reason I ask is that I am using a RPi-powered infrasonic sensor instrument ("Raspberry Boom") and I removed power during the final blink pattern, then discovered the device would not reboot upon reconnecting power. I had to tediously reflash the SD card, which did fix the issue. I suspect there is something about this particular device's hardware, the add-on board ("hat"?) that mounts on the RPi GPIO which may have some influence on that problem, but I might be wrong. I have removed power in this way from many other stand-alone Pi boards on many occasions, and do not recall having this problem before.