When I print to screen the driver input control lags

Programming Support VEXcode Pro V5 Text Tech Support
#1

So…when I run the code, it prints all 4 motor temperatures and velocity along with the battery percentage. But the driver input control has 1-2 second of lag between when I move the joysticks to when the robot actually moves. I commented all the code that prints to the controller and the lag disappears. How can I print to the controller and not have input lag at the same time?

// VEX V5 C++ Project
#include "vex.h"
using namespace vex;

//#region config_globals
vex::brain      Brain;
vex::motor      FrontLeft(vex::PORT1, vex::gearSetting::ratio18_1, false);
vex::motor      FrontRight(vex::PORT10, vex::gearSetting::ratio18_1, true);
vex::motor      BackLeft(vex::PORT11, vex::gearSetting::ratio18_1, false);
vex::motor      BackRight(vex::PORT20, vex::gearSetting::ratio18_1, true);
vex::controller Controller1(vex::controllerType::primary);
//#endregion config_globals

int main(void) {
    while(1){
    
    Controller1.Screen.setCursor(1,1);
    Controller1.Screen.print(FrontLeft.temperature(celsius));
    Controller1.Screen.print(" ");
    Controller1.Screen.setCursor(1,12);
    Controller1.Screen.print(FrontLeft.velocity(pct));
    Controller1.Screen.print(" ");
    
    Controller1.Screen.setCursor(2,1);
    Controller1.Screen.print(FrontLeft.temperature(celsius));
    Controller1.Screen.print(" ");
    Controller1.Screen.setCursor(2,12);
    Controller1.Screen.print(FrontLeft.velocity(pct));
    Controller1.Screen.print(" ");
    
    Controller1.Screen.setCursor(3,2);
    Controller1.Screen.print("Battery % full", (Brain.Battery.capacity())*100); 
    
    if(Controller1.Axis2.value() > 1){//Move Forward
        FrontLeft.spin(forward, 75, vex::velocityUnits(pct));
        FrontRight.spin(forward, 75, vex::velocityUnits(pct));
        BackLeft.spin(forward, 75, vex::velocityUnits(pct));
        BackRight.spin(forward, 75, vex::velocityUnits(pct));
    }
    else if(Controller1.Axis2.value() < -1){//Move Backward
        FrontLeft.spin(forward, 75, vex::velocityUnits(pct));
        FrontRight.spin(forward, 75, vex::velocityUnits(pct));
        BackLeft.spin(forward, 75, vex::velocityUnits(pct));
        BackRight.spin(forward, 75, vex::velocityUnits(pct));
    }
    else if(Controller1.Axis4.value() > 1){//Turn Left
        FrontLeft.spin(reverse, 75, vex::velocityUnits(pct));
        FrontRight.spin(forward, 75, vex::velocityUnits(pct));
        BackLeft.spin(reverse, 75, vex::velocityUnits(pct));
        BackRight.spin(forward, 75, vex::velocityUnits(pct));
    }
    else if(Controller1.Axis4.value() < -1){//Turn Right
        FrontLeft.spin(forward, 75, vex::velocityUnits(pct));
        FrontRight.spin(reverse, 75, vex::velocityUnits(pct));
        BackLeft.spin(forward, 75, vex::velocityUnits(pct));
        BackRight.spin(reverse, 75, vex::velocityUnits(pct));
    }
    else{
        FrontLeft.stop();
        FrontRight.stop();
        BackLeft.stop();
        BackRight.stop();
    }
    vex::sleep(1);
   }
 }
#2

Why do you need to continually (every 20ms) transmit motor temperatures and print it on the controller?

What this should tell you is that as an operation - sending data from brain to controller and printing it is an expensive operation.

2 Likes
#3

the sleep function currently is 1ms
I copied and pasted the modified code but I haven’t downloaded the new code yet
it was tested with 1ms I changed it to 20ms so later when I do download the modified code I can see if there is a difference
but 1ms for driver control has the best response I just don’t know how to not make the controller screen update that quickly

#4

Like @lacsap said, you shouldn’t need to update every 20 ms. If you need to keep such constant track of your motor temperatures, something is wrong.

My suggestion is make a separate task that updates every 3 seconds. Plenty of processing power is left to do the driver input. Then, program a button on the controller (one of the direction buttons would be my preference) to do a forced update of the controller screen. That way, if you just need to do a cursory glance during a match, you can without burning out your processing power, and if you really need it updated, then it’s not like you’re going to be driving while looking at the controller screen.

3 Likes
#5

so something like

if(Controller1.ButtonA.pressing(){
Controller1.Screen.setCursor(1,1);
Controller1.Screen.print(FrontLeft.temperature(celsius));
Controller1.Screen.print(" “);
Controller1.Screen.setCursor(1,12);
Controller1.Screen.print(FrontLeft.velocity(pct));
Controller1.Screen.print(” ");

#6

Sure. That isn’t how I would do it, but it would probably work.

#7

well…the compile worked I just need to download it tomorrow since I don’t have my robotics class today.

#8

Controller printing has some enforced delays due to wireless bandwidth.
If you try and print to the controller without at least a 50mS delay (when wireless, tethered is less), VEXcode will add the delay internally using task::sleep. The best approach is to run controller printing in a separate thread, that way only the printing thread is forced to sleep.

6 Likes
#9

Lies programmers tell themselves:

  • Memory is infinite
  • Bandwidth is infinite
  • Latency is zero
8 Likes