Error in IQ brain

Programming Support VEXcode IQ Technical Support
1

After downloading this code:

#region VEXcode Generated Robot Configuration
from vex import *
import urandom

# Brain should be defined by default
brain=Brain()

# Robot configuration code
brain_inertial = Inertial()
left_drive_smart = Motor(Ports.PORT6, 10.4, True)
right_drive_smart = Motor(Ports.PORT7, 10.4, False)

drivetrain = SmartDrive(left_drive_smart, right_drive_smart, brain_inertial, 200)
Lifter = Motor(Ports.PORT4, False)
H_Wheel = Motor(Ports.PORT5, False)
Combine = Motor(Ports.PORT10, False)



# Make random actually random
def setRandomSeedUsingAccel():
    wait(100, MSEC)
    xaxis = brain_inertial.acceleration(XAXIS) * 1000
    yaxis = brain_inertial.acceleration(YAXIS) * 1000
    zaxis = brain_inertial.acceleration(ZAXIS) * 1000
    urandom.seed(int(xaxis + yaxis + zaxis))
    
# Set random seed 
setRandomSeedUsingAccel()

vexcode_initial_drivetrain_calibration_completed = False
def calibrate_drivetrain():
    # Calibrate the Drivetrain Inertial
    global vexcode_initial_drivetrain_calibration_completed
    sleep(200, MSEC)
    brain.screen.print("Calibrating")
    brain.screen.next_row()
    brain.screen.print("Inertial")
    brain_inertial.calibrate()
    while brain_inertial.is_calibrating():
        sleep(25, MSEC)
    vexcode_initial_drivetrain_calibration_completed = True
    brain.screen.clear_screen()
    brain.screen.set_cursor(1, 1)

#endregion VEXcode Generated Robot Configuration



global distTraveled
def posPID(setPoint): 
    wTime = 15
    distTraveled = 0
    prevError = 0
    integral = 0
    arrive = False
    while arrive == False: #some condition 
        error = setPoint - distTraveled
        integral = integral + error
        if error == 0:
            integral = 0
        if error < 0:
            integral = 0
            derivative = error - prevError
            prevError = error      
        kP = 1
        kI = 1
        kD = 1 # to be set later
        power = error*kP + integral*kI + derivative*kD
        drivetrain.stop()
        drivetrain.set_drive_velocity(power, PERCENT)
        drivetrain.drive(FORWARD)
        distTraveled = drivetrain.velocity(RPM) * 200 * wTime
        wait(wTime)
        if error == setPoint:
            arrive = True     
        pass

pass    
distTraveled = 0
posPID(100)

and running it, I get this error on the robot brain.

Traceback (most recent call last)
     File "userpy", line 83. in <module>
     File "userpy", line 69. in posPID
  NameError: local variable referenced b

First, how do I see the rest of the error (after the b)
Second, does anybody know what this means?

I haven’t used python in a while so it might just be wrong syntax

2

on the python console. not much space on the brain.

the full error was

>>> Traceback (most recent call last):
  File "userpy", line 82, in <module>
  File "userpy", line 70, in posPID
NameError: local variable referenced before assignment

and caused by derivative being used before ever being assigned a value

5 Likes
3

Thanks, I have a comp on saturday and this helps alot!

1 Like