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SERVO4: Quad PWM Servo Controller
SERVO4 controls four hobby servos with 50 nanosecond resolution per servo.
The Quad Servo Controller provides four outputs that can each control one PWM servo motor. The servo pulse widths are accurate to 50 nanoseconds. The cycle time on each of the four signals is 20 milliseconds.>/p>
Normal servo motors expect a pulse width in the range of 1000000 to 2000000 nanoseconds. A 50 nanoseconds resolution gives 20000 different valid values or over 14 bits of accuracy.
The servos are numbered from 1 to 4 with servo 1 on the lowest numbered pin on the interface card. You can wire your own interface but SERVO4 is most often paired with the GPIO card. More information about the GPIO card can be found here: GPIO card.
positions : pulse widths in nanoseconds. Positions has four space-separated pulse widths in nanoseconds and terminated by a newline. A pulse width of zero sets that output high and pulse width of -1 keeps the current position for that servo. A dpget on the positions resource returns the current positions of all four servos.
Move all pulse widths to center, then move just servo 1 and 3 but not 2 and 4.
dpset servo4 servogroup 1500000, 1500000, 1500000, 1500000 dpset servo4 1400000 -1 1600000 -1