STM32MagneticSensorPWM::getSensorAngle() can underflow when getDutyCycleTicks() returns a value below min_ticks.

[thomasfla]

Arduino-FOC-drivers/src/encoders/stm32pwmsensor/STM32MagneticSensorPWM.cpp

Line 29 in ed05aa1

return (ticks - min_ticks) * _2PI / (max_ticks - min_ticks);

Current behavior:

uint32_t ticks = getDutyCycleTicks();
return (ticks - min_ticks) * _2PI / (max_ticks - min_ticks);

Since ticks and min_ticks are unsigned, ticks < min_ticks wraps to a huge value. On an AS5048A PWM sensor near the zero boundary I see:

duty_ticks=152 angle=705512.000000 velocity=7055119.500000

Expected: values below min_ticks should clamp or be rejected.

Possible fix:

uint32_t ticks = getDutyCycleTicks();
ticks = constrain(ticks, min_ticks, max_ticks);
return (ticks - min_ticks) * _2PI / (max_ticks - min_ticks);

[runger1101001]

Hey Thomas, thank you for reporting it!!

I’ll try to add a constrain like you suggest in the next release.

Note that the AS5048A uses values < min to report back errors. Really a chip-specific driver should account for that, and not treat a <min value as equal to min, but probably keep the last good value as the current angle. But for the generic driver your suggested fix is the right approach.