How do I get immediate response between motors and sensors?

Question

I am new to pybricks and have found very little documentation to help answer my own query. I have written what I thought would be a simple program to spin my robot on the spot until the UltrasonicSensor sees something. It will then push forwards. If it is pushed backwards and sees a black line, it should try and swing out of the way.

The following code "works", but it's response to the Ultrasonic and Light sensors is significantly delayed:

#!/usr/bin/env pybricks-micropython

from pybricks.hubs import EV3Brick
from pybricks.ev3devices import Motor, ColorSensor, UltrasonicSensor
from pybricks.parameters import Port
from pybricks.tools import wait

ev3 = EV3Brick()
eyes = UltrasonicSensor(Port.S2)
left_motor = Motor(Port.B)
right_motor = Motor(Port.A)
right_light = ColorSensor(Port.S1)
left_light = ColorSensor(Port.S4)

while True:

    if right_light.reflection() < 50:
        ev3.speaker.say('black')
        left_motor.run(500)
        right_motor.run(-100)
        wait(2000)
        left_motor.run(500)
        right_motor.run(500)
        wait(1000)
    if eyes.distance() > 200:
        left_motor.run(500)
        right_motor.run(-500)
    else:
        left_motor.run(-500)
        right_motor.run(-500)

I can see in the (limited) documentation that you can apparently change motor settings but I can't find direction on how to do this (or even if it would be useful). Any help would be appreciated.

score 3 · Answer 1 · answered Jan 13 '21 at 09:01

3

ev3.speaker.say(text) synthesizes speech as it goes. This is fun, but it is very slow. This is especially noticeable in a control loop like yours.

I'd recommend using ev3.speaker.beep() instead. You could even select the frequency based on the reflection value so you can "hear" what the sensor "sees".

answered Jan 13 '21 at 09:01

Laurens Valk

66
5

Thank you for your reply. It hasn't stopped the lag between sensor and motor though. I feel like the motor is needing to accelerate to the speed I've given it and then decelerate from that speed before it responds. Is this is a thing? Is there a way to remove all accel/decel and just immediately perform the next command? The old NXT bricks worked that way?!? – MisterWeary Jan 13 '21 at 22:59

score 2 · Accepted Answer · answered Jan 13 '21 at 23:17

2

So the problem was that I used the "run" command to move the motors. Run appears to have an acceleration and deceleration component.

I used "dc" instead of "run" and the motors instantly respond to the sensor data now.

answered Jan 13 '21 at 23:17

MisterWeary

605
1
9
16

How do I get immediate response between motors and sensors?

2 Answers2