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parallaxinc / Simple-Libraries

Contents of the SimpleIDE workspace folder and its Parallax Learn Simple Libraries subfolder.
http://learn.parallax.com/propeller-c-set-simpleide/update-your-learn-folder
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servo360 - prevent binary overflow of 12-bit angle #92

Closed AndyLindsay closed 6 years ago

AndyLindsay commented 6 years ago

The servo360 library needs code added to prevent binary overflow in its angle tracking. Overflow will happen after 524000 revolutions. That could happen after 72 hours of top speed 120 RPM rotation in a given direction.

AndyLindsay commented 6 years ago

The actual time it takes to overflow will be less because the measured angle is multiplied by certain values.

AndyLindsay commented 6 years ago

I think we might see the highest values from these calculations in API_PUBLIC.c: offset = fb[p].angleTarget; target = position * UNITS_ENCODER / fb[p].unitsRev; fb[p].angleTarget = target + offset;

Rollover will be at 2^31 / 2^12 = 2^19 = 524,288 turns. 524,288 turns (1 s / 2 turns) (1 min / 60 s) * (1 hr / 60 min) = 72.8 hours

Max degree units = 188,743,680.

Max ActivityBot units (64ths) = 33, 554, 432.

Search term: ].angle

AndyLindsay commented 6 years ago

It's probably best to start by writing a reset function that the user can call after checking and and finding that the angle is approaching 188 M degrees, or 33 M ActivityBot encoder ticks, or maybe just 500,000 turns.

AndyLindsay commented 6 years ago

Commit: Fix servo360 - Prevent binary overflow of 12-bit angle (Issue 92)

Added functions for checking and setting the number of turns. Example programs that use the functions are in:

in ...Documents\SimpleIDE\My Projects\Tests Servo360\