Keyestudio KS4028 Manual page 283

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The rotation angle of servo motor is controlled by regulating the duty cycle
of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM
signal is 20ms (50Hz). Theoretically, the width is distributed
between 1ms-2ms, but in fact, it's between 0.5ms-2.5ms. The width
corresponds the rotation angle from 0° to 180°. But note that for different
brand motors, the same signal may have different rotation angles.
Through the experiment, the pulse range of the servo is 0.65ms~2.5ms.
high level Servo angle Reference signal cycle time（20ms）
time
0.65ms 0° 0.65ms high level+19.35mslow level
1.5ms 90° 1.5ms high level+18.5mslow level
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