Servos

Servos are a bit like motors, except their position is fixed. This is useful for building an arm mechanism that grabs cubes, or anything else that has fixed states that it needs to be in.

Similarly to motors, the position of a servo is expressed as a percentage. This can be negative.

Servos are plugged into the Servo ports on the BrainBox. The numbers present on each port correspond to the index used in your code.

Python

Servo control is provided by the io subsystem of the robot library. You will need to import the IO object and various constants from this module before using servos.

You can control servos using the servos property of the IO object. To set the servo 0 to the 50% position use:

I.servos[0].mode = PWM_SERVO
I.servos[0] = 50

Tip

For example, to control servo 3 instead, replace servos[0] with servos[3]. Again, remember that indexes start at 0.

Here’s a more complete example, controlling servos 0 and 1:

from robocon.io import *
import time

I = IO()
I.servos[0].mode = PWM_SERVO
I.servos[1].mode = PWM_SERVO

# set servo 0 to the 50% position
I.servos[0] = 50

# wait for the servo to finish moving
time.sleep(1)

# set servo 1 to the -100% position
I.servos[1] = -100

time.sleep(1)

# set servos 0 & 1 to the default positions
I.servos[0] = 0
I.servos[1] = 0

Tip

Add a delay with time.sleep to wait for the servos to finish moving into their new positions.

Blockly

Blocks for controlling servos can be found in the Movement section.

Setting initial servo position

The initial position of servos can be set before your code starts running using project attributes. Values can be any integer between -100 and 100 inclusive.

Attribute	Values
servo0_pos	x ∈ [-100, 100] ∩ ℤ	Initial position of servo 0
servo1_pos	x ∈ [-100, 100] ∩ ℤ	Initial position of servo 1
servo2_pos	x ∈ [-100, 100] ∩ ℤ	Initial position of servo 2
servo3_pos	x ∈ [-100, 100] ∩ ℤ	Initial position of servo 3