Servo Library  v0.9
Servo motor control library for educational and hobby applications
Functions
servo.h File Reference

Control up to 14 servos in other cog. For up to 28, add the servoAux library to your project. Control the first 14 with servo_set, servo_speed, servo_angle, and other servo_ function calls. Control servos 15 and up with the same function calls, but starting with servoAux_ instead of servo_.

Currently supports LMM and CMM memory models.
servo library launches a single cog for controlling 1st to 14th servos
servoAux library launches an additional cog for controlling the 15th through 28th servos. More...

#include "simpletools.h"

Go to the source code of this file.

Functions

int servo_angle (int pin, int degreeTenths)
 Set Parallax Standard Servo to angle from 0 to 180 in tenths of a degree.
int servo_speed (int pin, int speed)
 Set Parallax Continuous Rotation servo speed.
int servo_setramp (int pin, int stepSize)
 Set the maximum change in control signal a servo will change in a given 20 ms time period.
int servo_set (int pin, int time)
 Sets servo control signal to servo connected to a given pin for microsecond pulse durations.
int servo_get (int pin)
 Reports the number of microseconds of the pulse most recently sent to a given servo.
void servo_stop (void)
 Stops the servo process and frees a cog.
int servo_start (void)
 Starts the servo process and takes over a cog.

Detailed Description

Control up to 14 servos in other cog. For up to 28, add the servoAux library to your project. Control the first 14 with servo_set, servo_speed, servo_angle, and other servo_ function calls. Control servos 15 and up with the same function calls, but starting with servoAux_ instead of servo_.

Currently supports LMM and CMM memory models.
servo library launches a single cog for controlling 1st to 14th servos
servoAux library launches an additional cog for controlling the 15th through 28th servos.

Author
Andy Lindsay
Version
0.9

This library automatically delivers control pulses to the servos every 20 ms, all you have to do is use the set method to pick the pin the servo is connected to and the duration of the control pulses.

Parallax standard servos have a position range from approximately 0 to 180 degrees.


Please submit bug reports, suggestions, and improvements to this code to edito.nosp@m.r@pa.nosp@m.ralla.nosp@m.x.co.nosp@m.m.

Function Documentation

int servo_angle ( int  pin,
int  degreeTenths 
)

Set Parallax Standard Servo to angle from 0 to 180 in tenths of a degree.

Examples:

servo_angle(pin, 0); // for 0 degrees
servo_angle(pin, 900); // for 90 degrees
servo_angle(pin, 1800); // for 180 degrees

0 to 1800 corresponds to control pulses ranging from 500 to 2300 with 1400 at center (90 degrees), which is slightly different from the 1500 center convention, but it places the Parallax Standard Servo's range of motion neatly between its mechanical limits.

Parameters
pinNumber of the I/O pin connected to servo
degreeTenthsTenths of a degree from 0 to 1800
Returns
pin number = success, -1 = no cogs available, -2 = no locks available, -3 = all 14 servo slots already filled.
int servo_get ( int  pin)

Reports the number of microseconds of the pulse most recently sent to a given servo.

Parameters
pinNumber of the I/O pin the servo is connected to
Returns
tp[i] The value stored by the array element that keeps duration of the most recent pulse sent to the servo. (Or -4 if an entry is not found for the pin argument.
int servo_set ( int  pin,
int  time 
)

Sets servo control signal to servo connected to a given pin for microsecond pulse durations.

This function directly controls the number of microseconds servo control pulses last.

Examples for Parallax Standard Servo:

servo_set(pin, 500); // 0 degrees
servo_set(pin, 1400); // 90 degrees
servo_set(pin, 2300); // 180 degrees

500, 1400, and 2300 are the number of microseconds (us) the control pulses stay high. More generally, a microsecond above 500 corresponds to 1/10 of a degree counterclockwise of 0 degrees. So, for a given degree position, use:

degree position = 500 + (number of 10ths of a degree)

For setting Parallax Continuous Rotation Servo speed, use:

  • Full speed clockwise -> servo_set(pin, 1400);
  • Stay still -> servo_set(pin, 1500);
  • Full speed counterclockwise -> servo_set(pin, 1600);

Values in the 1400 to 1600 range are (roughly) proportional to speed for a Parallax Continuous Rotation Servo, but it's not nearly as precise as position control. Setting full speeds at 1300 and 1700 is a common practice to make sure both servos are going as fast as they possibly can.

Parameters
pinNumber of the I/O pin that sends signals to the servo.
timeMicrosecond servo pulse time.
Returns
pin number = success, -1 = no cogs available, -2 = no locks available, -3 = all 14 servo slots already filled.
int servo_setramp ( int  pin,
int  stepSize 
)

Set the maximum change in control signal a servo will change in a given 20 ms time period.

This function allows you to make a Parallax Continuous Rotation servo ramp up to and down from whatever speed or position it was previously set to. It also allows you to set the rate at which a Parallax Standard servo turns from its previous position to a new position.

Parameters
pinNumber of the I/O pin the servo is connected to
stepSizeThe number of microseconds per 20 ms of time that the servo's control signal is allowed to change. This equates to the number of tenths of a degree a Parallax Standard servo is allowed to change, or the number of 100ths of full speed the a Parallax Continuous Rotation servo is allowed to change per 20 ms.
Returns
pin if successful, -4 if pin not found.
int servo_speed ( int  pin,
int  speed 
)

Set Parallax Continuous Rotation servo speed.

Examples:

servo_speed(pin, 200); // Twice full speed counterclockwise
servo_speed(pin, 100); // Full speed counterclockwise
servo_speed(pin, 0); // Stay still
servo_speed(pin, -100); // Full speed clockwise
servo_speed(pin, -200); // Twice full speed clockwise

100 to -100 corresponds to the linear speed control range. For example, servo_speed(pin, 75) will set the speed to roughly 75% of full speed counterclockwise. This is a very rough approximation.

Parameters
pinNumber of the I/O pin connected to servo
speedSpeed from -100 to 100
Returns
pin number = success, -1 = no cogs available, -2 = no locks available, -3 = all 14 servo slots already filled.
int servo_start ( void  )

Starts the servo process and takes over a cog.

You do not need to call this function from your code because the servo_set function calls it if it detects that the servo cog has not been started.

Returns
1..8 if successful. 0 if no available cogs, -1 if no available locks.