I'm making a door open timer using a hall sensor and have a wemos d1 mini that uses a deep sleep to sleep for 1 minute after checking the hall sensor state and printing the value on the serial port. I'm using the Arduino IDE to monitor the serial output and have the Show timestamp option enabled so that I could time how long the device is running after it resets. However, I'm getting output like this:
08:03:26.286 -> ^H⸮ȸ$RKx⸮⸮x⸮I⸮⸮696 08:04:25.454 -> HEA⸮⸮⸮d⸮⸮⸮⸮⸮⸮⸮696 08:05:24.681 -> ⸮⸮NI⸮ hlE⸮0⸮/⸮696 08:06:23.915 -> ⸮DP⸮V⸮l⸮X⸮X⸮H⸮⸮694 08:07:23.178 -> ⸮A⸮K`E⸮M⸮⸮xxE⸮696 08:08:22.406 -> ⸮HlX⸮K⸮I|⸮⸮xE⸮693 08:09:21.703 -> ⸮⸮NI⸮ hlE⸮0⸮⸮E⸮694 08:10:20.978 -> 8H⸮JcD⸮M⸮⸮xxE⸮695 08:11:20.306 -> ⸮⸮NI⸮AhlE⸮ Op⸮⸮696 08:12:19.573 -> ⸮⸮NI⸮ hlE⸮0⸮/⸮539 08:13:18.897 -> ⸮⸮OI⸮AhlE⸮⸮O⸮⸮538 08:14:18.196 -> HEA⸮⸮⸮d⸮⸮⸮⸮I⸮⸮539 08:15:17.561 -> ⸮dG⸮⸮⸮hLJ⸮@h⸮⸮(⸮539
The garbage output isn't what I'm asking about, it's the timestamps being created by the arduino ide. Since I sleep for 60,000,000 microseconds, I would assume that the second value of the minute would be slightly more each time. But as shown above, it becomes slightly less every time, as if it takes less than a minute. So what I'm wondering is if the sleep timer on these devices is not accurate enough to count on this or something else I should be considering like an inaccuracy in the IDE? I only wanted to measure the uptime so that I could consider it for battery drain considerations, I don't really need a millisecond accurate timer for the functionality of the device.