Neobotics Foundation Inc.
First programNEORACER DOCS
NEORACER DOCS
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STEP 05 / GETTING STARTED · THE FINAL ONE

HELLO, RACECAR.

Twenty lines of Python that drive a one-metre square. The exact same script runs in the NeoRacer Playground simulator and on the car, your choice where to try it first.

0 minutesBeginnerSim ↔ Car parity
FIG. A / WHAT YOUR PROGRAM WILL DO
DRIVING PATH · ~1 m PER SIDESTART / END1 s forwardturn 90°1 s forwardturn 90°
Forward one second, turn 90°, repeat four times. The simplest possible closed-loop program, open-loop in this case, since we don't check sensors yet.
//Pick your launch pad
  • Playground (recommended for the first run): zero install. Open playground.neobotics.org in your browser, paste the code, and you're one click from Run.
  • Car: into the Jetson (covered in Networking) and run the script over ros2 run with the racecar-neo-library installed.
01 / THE PROGRAM

THE PROGRAM.

python
import racecar_core

rc = racecar_core.create_racecar()

SIDE_TIME = 1.0   # seconds per straight leg
TURN_TIME = 0.7   # seconds per 90-degree turn
SPEED = 0.25      # 25% throttle
TURN = 1.0        # full lock

timer = 0.0
leg = 0           # 8 legs: even legs drive straight, odd legs turn

def start():
    global timer, leg
    timer, leg = 0.0, 0
    rc.drive.stop()

def update():
    global timer, leg
    if leg >= 8:                     # four straights + four turns
        rc.drive.stop()
        return
    timer += rc.get_delta_time()     # seconds since the last frame
    if leg % 2 == 0:                 # straight leg
        rc.drive.set_speed_angle(SPEED, 0)
        if timer > SIDE_TIME:
            leg, timer = leg + 1, 0.0
    else:                            # turn leg
        rc.drive.set_speed_angle(SPEED, TURN)
        if timer > TURN_TIME:
            leg, timer = leg + 1, 0.0

rc.set_start_update(start, update)
rc.go()
02 / WHAT TO EXPECT

WHAT TO EXPECT.

The car traces something roughly square and lands near, but not exactly on, its start. That gap is the whole reason sensors exist, and feeling it for yourself here makes that click into place.

Sim run
Path looks geometric. Corners are sharp. Final position drifts about 10 cm.
Car run (carpet)
Path skews. Final position can drift 50 cm or more. Carpet wheel slip is the dominant error.
Car run (hardwood)
Closer to the sim. Drift comes from un-trimmed servo and motor torque ripple.