Douglas Halse

The web server is run on a local hotspot that the raspberry pi itself creates and that enables users that are connected to the hotspot ability to issue commands to the car.

The code is very simple and works by taking in HTML requests for directories such as “/control_accel_on” which sets the proper GPIO pin to start the accelerator on the car. The issuer of that command then has the responsibility to also send a request for the “/control_accel_off” directory to make sure the car does not goes off and put a hole in my wall.

The issuer of the commands is also responsible to not engage the accelerator and the reverse action at the same time to avoid damage to the motors.

To issue the web page request i decided to run a second python script that uses a configured bluetooth connected controller to read input. The processing of the inputs took some time but i managed to read the values of both triggers for accelerating and reversing and the directional buttons for steering.

The triggers on the controller returned a value between 0 and 255 so a had to interpret anything above 127 as the button being activated. The directional pad on the other hand shared button id but returned different values depending on what direction was pressed.

A great tutorial on how to read bluetooth commands for your own project can be found here.

Any read command simply issued a HTML open request using pythons urllib.request library.

Python Flask web server

import RPi.GPIO as GPIO
from flask import Flask, render_template, redirect, url_for, request, flash, g
#GPIO and pin setup
left = 17; right = 27; backward = 22; forward = 10
GPIO.setmode(GPIO.BCM); GPIO.setup(17, GPIO.OUT); GPIO.setup(27, GPIO.OUT); GPIO.setup(22, GPIO.OUT); GPIO.setup(10, GPIO.OUT)

app = Flask(__name__)
@app.route("/control_accel_on")
def control_accel_on():
    GPIO.output(forward, GPIO.HIGH)
    return "1"
@app.route("/control_accel_off")
def control_accel_off():
    GPIO.output(forward, GPIO.LOW)
    return "1"
@app.route("/control_rever_on")
def control_rever_on():
    GPIO.output(backward, GPIO.HIGH)
    return "1"
@app.route("/control_rever_off")
def control_rever_off():
    GPIO.output(backward, GPIO.LOW)
    return "1"
@app.route("/control_steer_left")
def control_steer_left():
    GPIO.output(left, GPIO.HIGH)
    return "1"
@app.route("/control_steer_right")
def control_steer_right():
    GPIO.output(right, GPIO.HIGH)
    return "1"
@app.route("/control_steer_idle")
def control_steer_idle():
    GPIO.output(left, GPIO.LOW)
    GPIO.output(right, GPIO.LOW)
    return "1"