Copyright © Parallax Inc. Parallax Continuous Rotation Servo (#900-00008) v2.2 10/24/2011 Page 7 of 8
FOR counter = 1 TO 100 ' Hold still for ~3 seconds
PULSOUT servoPin, 750
PAUSE 20
NEXT
FOR counter = 1 TO 100 ' Rotate clockwise for ~3 seconds
PULSOUT servoPin, 650
PAUSE 20
NEXT
END
For more examples with the BASIC Stamp 2, incl uding 2-wheeled robot maneuvers and ramping, see
Robotics with the Boe -Bot
Chapter 4 , available for free downl oad from the 28132 product page at
www.parallax.com.
Propeller
™
P8X32A Application
The program below uses counter modules to rotate the servo first clockwise at full speed for 2 seconds,
then rests for 2 seconds, and rotates counterclockwise at full speed for another 2 seconds. This code can
also be downloaded from the 900-00008 product page.
{{ ServoContinuousRotation.spin
Turn Parallax Continuous Rotation Servo clockwise full speed for 21 sec.
hold still 2 sec, and then counterclockwise full speed for 2 sec. }}
CON
_clkmode = xtal1 + pll16x ' System clock → 80 MHz
_xinfreq = 5_000_000 ' Using 5 MHz external crystal oscillator
servoPin = 0 ' Servo signal to this I/O pin-change if needed
PUB CenterServo | tInc, tc, tCtr, tCw, tCcw, t
ctra[30..26] := %00100 ' Configure Counter A to NCO
ctra[8..0] := servoPin
frqa := 1
dira[servoPin]~~
tInc := clkfreq/1_000_000 ' 1 μs increment
tC := tInc * 21_500 ' Low pulse
tCtr := tInc * 1500 ' Center pulse = 1.5 ms
tCw := tInc * 1300 ' Clockwise fast = 1.3 ms
tCcw := tInc * 1700 ' Counter-Clockwise fast = 1.7 ms
t := cnt ' Mark counter time
repeat 100 ' Repeat PWM signal 100x
phsa := -tCw ' Set up clockwise fast pulse
t += tC ' Calculate next cycle repeat
waitcnt(t) ' Wait for next cycle (20 ms)
repeat 100 ' Repeat PWM signal 100x
phsa := -tCtr ' Set up the center pulse
t += (tC + 200) ' Calculate next cycle repeat
