Raspi Car

• A Raspberry Pi Zero W
    A Raspberry Pi Zero W is a small single board computer made by the Raspbery Pi Foundation. For more information visit https://www.raspberrypi.org/ . It is perfect because of it's small size and built in Wifi.
• Micro SD Card
    The Raspberry Pi will need one on which to install the OS. An 8GB or even a 4GB SD card for th OS is sufficient for this project.
• USB Web Cam
    I recommend a Creative - Live! Cam which runs about $20.00. You may be able to find a less expensive one on ebay, just avoid shipments from China.
• OTG micro USB-to-USB
    The Raspberry Pi USB input is a micro type so you will needed this to connect the camera to the Pi.
• RC Car
    Maybe the most difficult component to get. Newer cars in the stores use LiPo batteries and have smaller electronics making them difficult to use. Thrift stores like Salvation Army or Goodwill are the best places. The transmitter won't be needed, so buy it even if it doesn't have one. Having said that, the cars there are sort of hit or miss. Often times they may not work, but for a price of 4-6 dollars a couple of duds won't break the bank. If you have bought more duds than you wanted and are feeling ambitious you could hobble together a car from working parts. If you are unable to find one with a battery you will need to purchase one which will increase the cost. When buying a car note the voltage required. Some cars use standard double A batteries and only run on 6 volts. Those will be difficult to use. For this guide I will use a 9.6 volt battery.
• NiCad Battery
    If you are unable to find an RC car with one you will need to get a seperate battery. You may decide in the future to get a higher capacity battery for more run time. A custom battery from Battery giant is what I used. A custom battery needs to have the Tamiya style connectors.
• A USB Charging Adapter.
    One that would be used in a car outlet. This will drop the voltage down from 9.6v to 5v, The operating voltage for the Raspberry Pi.
• Jumper wires
    Male to female.
• Wire
    26 or 24 gage; If you can, get both black and red to keep it color coded.
• Tamiya Big Style Connector Plugs
    Unwired. Connecter that RC car batteries use. If you get a custom battery make sure they use this style connector. Additional ones will be used to connect the car charger to the battery.
• Mini HDMI Adapter or Cable
    The Raspberry Pi Zero uses a mini HDMI port. This will only be used in the intial stages of setup, leaving the adapter available for other projects.

Download Raspbian

You can get this image via direct download or torrent here. The regular version comes with a graphical user interface and will occupy more disk space. Get the lite version because there will be no need for the user interface. Every thing in this guide can be done with the command line interface.

Download Win32 Disk Imager

The executable may be found here. Extract the .img file from your Raspbian download and run the disk imager. Select the file you extracted and your SD Card. Click Write to install the OS. After that is done it is time to boot the Pi. Insert the SD card and connect it to a TV or monitor via HDMI. Connect a keybord then provide power. After it boots, login with the default user name "pi" and password "raspberry". Before anything we need to get the device onto the WiFi. (For a more detailed guide check here.)

Set up WiFi

To edit the supplicant file and enter your WiFi credentials, run:

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

Add these lines to the bottom.

network={
        ssid="name_of_wifi"
        psk="passkey_of_wifi"
}

Press ctrl-X, save and exit.

Enable SSH

By default on Raspbian SSH is disabled. To enable it run:

sudo systemctl enable ssh 
sudo systemctl start ssh

Reboot by running

sudo reboot

Once it has rebooted login and type

ifconfig

Note the IP address. If there is not ip address listed then check the file for WiFi. The Pi may now be disconnected from the TV/monitor and keyboard; they are no longer needed. Further interfacing with the Pi can be done remotely with an SSH client. WinSCP or MobaXterm will work. Select your favorite and log into the IP address from before with the default username and password.

Before we enter any commands we we want to update the Pi to the latest. Run:

sudo apt-get update
sudo apt-get upgrade

Node Red will hadle the web pages and controlling the GPIOs. For a detailed setup guide visit Node-RED : Running on Raspberry Pi

To get the latest node red for Raspberry Pi run:

bash <(curl -sL https://raw.githubusercontent.com/node-red/raspbian-deb-package/master/resources/update-nodejs-and-nodered)

To create the settings file for Node-Red it needs to be started once. Run:

sudo systemctl start nodered

We need to tell Node-Red where to look for the web page assets. This will become the root directory for any web pages served by http nodes. Run:

nano /home/pi/.node-red/settings.js

And change the line:
//httpStatic: '/home/nol/node-red-static/',
to:
httpStatic: '/home/pi/.picar/www/,

Press ctrl-X, save and exit.

Now we need to copy the web asstets into the folder that was specified in the settings. Create the directories by running:

mkdir /home/pi/.picar
mkdir /home/pi/.picar/www

Download the web assets here picar-nodered-www.zip. Unzip and copy the www directory into /home/pi/.picar with your ssh client.

Restart Node-Red:

sudo systemctl restart nodered

Node-Red uses graphical "nodes" to layout a program which it will execute. By connecting these nodes different programs can be written without much actual code. These layouts are called workflows.

To set up the program for this project I have provided three flows to import: Web Server, Control, and Credentials. You can access Node-Red by opening a browser to the Pi's ip address on port 1880 in the node-red directory e.g. ( http://ip_address:1880).

Web Server

Open the menu in the top right of the screen and select Import > Clipboard Paste the following into a new flow.

[
{
    "id": "acc22612.1a8258",
    "type": "file in",
    "z": "1fee60dc.191fff",
    "name": "auth.html",
    "filename": "/home/pi/.picar/www/auth.html",
    "format": "utf8",
    "sendError": true,
    "x": 520,
    "y": 80,
    "wires": [
        [
            "aff0c571.204548"
        ]
    ]
},
{
    "id": "9d08714e.9b236",
    "type": "function",
    "z": "1fee60dc.191fff",
    "name": "Get Submitted",
    "func": "var driver = msg.payload.driver.toLowerCase();\nvar key = msg.payload.key;\n\nmsg.driver = driver;\n\nvar keyObject = {};\nkeyObject[driver] = key;\n\nmsg.payload = JSON.stringify(keyObject);\nreturn msg;",
    "outputs": 1,
    "noerr": 0,
    "x": 160,
    "y": 100,
    "wires": [
        [
            "32ae2dc5.59e942"
        ]
    ]
},
{
    "id": "ab57849c.aa3bc8",
    "type": "function",
    "z": "1fee60dc.191fff",
    "name": "Store Hash",
    "func": "msg.key = msg.payload;\nreturn msg;",
    "outputs": 1,
    "noerr": 0,
    "x": 150,
    "y": 180,
    "wires": [
        [
            "b8ae7304.33a36"
        ]
    ]
},
{
    "id": "b8ae7304.33a36",
    "type": "file in",
    "z": "1fee60dc.191fff",
    "name": "keys",
    "filename": "/home/pi/.picar/www/keys",
    "format": "utf8",
    "sendError": true,
    "x": 130,
    "y": 220,
    "wires": [
        [
            "812830b9.9fe19"
        ]
    ]
},
{
    "id": "812830b9.9fe19",
    "type": "json",
    "z": "1fee60dc.191fff",
    "name": "",
    "x": 130,
    "y": 260,
    "wires": [
        [
            "b6755af4.76fc78"
        ]
    ]
},
{
    "id": "b6755af4.76fc78",
    "type": "function",
    "z": "1fee60dc.191fff",
    "name": "Validate",
    "func": "var keyRing = msg.payload;\nvar driver = msg.driver.toLowerCase();\nvar key = msg.key;\n\nif (keyRing[driver] && keyRing[driver] === key) {\n    keyobject = {};\n    keyobject[driver] = key;\n    msg.cookies = {\n        carkey: {\n            value: JSON.stringify(keyobject),\n            maxAge: 10*365*24*60*60*1000\n        }\n    }\n    msg.payload = 'succeeded';\n    return msg\n}\nmsg.payload = 'failed';\nreturn msg;",
    "outputs": "1",
    "noerr": 0,
    "x": 140,
    "y": 300,
    "wires": [
        [
            "3b5b91b6.7d3a4e"
        ]
    ]
},
{
    "id": "3b5b91b6.7d3a4e",
    "type": "http response",
    "z": "1fee60dc.191fff",
    "name": "",
    "x": 270,
    "y": 300,
    "wires": []
},
{
    "id": "aff0c571.204548",
    "type": "http response",
    "z": "1fee60dc.191fff",
    "name": "",
    "x": 650,
    "y": 80,
    "wires": []
},
{
    "id": "d82fa1aa.d92c7",
    "type": "http in",
    "z": "1fee60dc.191fff",
    "name": "",
    "url": "/picar",
    "method": "get",
    "upload": false,
    "swaggerDoc": "",
    "x": 360,
    "y": 60,
    "wires": [
        [
            "3bd7d0a7.acf3a"
        ]
    ]
},
{
    "id": "a6603349.42ce1",
    "type": "file in",
    "z": "1fee60dc.191fff",
    "name": "keys",
    "filename": "/home/pi/.picar/www/keys",
    "format": "utf8",
    "sendError": true,
    "x": 350,
    "y": 140,
    "wires": [
        [
            "92e3b880.587308"
        ]
    ]
},
{
    "id": "92e3b880.587308",
    "type": "json",
    "z": "1fee60dc.191fff",
    "name": "",
    "x": 350,
    "y": 180,
    "wires": [
        [
            "4fa6a0c2.68daa"
        ]
    ]
},
{
    "id": "4fa6a0c2.68daa",
    "type": "function",
    "z": "1fee60dc.191fff",
    "name": "Validate",
    "func": "var keyring = msg.payload;\nvar submitted = msg.submitted;\nvar driver = Object.keys(submitted)[0].toLowerCase();\n\nvar key = submitted[driver];\n\nif (keyring[driver] && keyring[driver] === key) {\n    return [null, msg];\n}\n\nreturn [msg, null];\n",
    "outputs": "2",
    "noerr": 0,
    "x": 360,
    "y": 220,
    "wires": [
        [
            "eba92dae.3e76e"
        ],
        [
            "ea78a51.6065e58"
        ]
    ]
},
{
    "id": "eba92dae.3e76e",
    "type": "file in",
    "z": "1fee60dc.191fff",
    "name": "auth.html",
    "filename": "/home/pi/.picar/www/auth.html",
    "format": "utf8",
    "sendError": true,
    "x": 500,
    "y": 200,
    "wires": [
        [
            "7a0630ad.57f1d"
        ]
    ]
},
{
    "id": "7a0630ad.57f1d",
    "type": "http response",
    "z": "1fee60dc.191fff",
    "name": "",
    "x": 630,
    "y": 220,
    "wires": []
},
{
    "id": "ea78a51.6065e58",
    "type": "file in",
    "z": "1fee60dc.191fff",
    "name": "main.html",
    "filename": "/home/pi/.picar/www/main.html",
    "format": "utf8",
    "sendError": true,
    "x": 500,
    "y": 240,
    "wires": [
        [
            "7a0630ad.57f1d"
        ]
    ]
},
{
    "id": "2da48ba9.6645b4",
    "type": "http in",
    "z": "1fee60dc.191fff",
    "name": "",
    "url": "/picar",
    "method": "post",
    "upload": false,
    "swaggerDoc": "",
    "x": 150,
    "y": 60,
    "wires": [
        [
            "9d08714e.9b236"
        ]
    ]
},
{
    "id": "3bd7d0a7.acf3a",
    "type": "function",
    "z": "1fee60dc.191fff",
    "name": "Get Cookie",
    "func": "var c = msg.req.cookies;\nif (c.carkey){\n    msg.payload = c.carkey;\n    msg.submitted = JSON.parse(c.carkey);\n    return [null, msg];\n}\nreturn [msg, null]",
    "outputs": "2",
    "noerr": 0,
    "x": 370,
    "y": 100,
    "wires": [
        [
            "acc22612.1a8258"
        ],
        [
            "a6603349.42ce1"
        ]
    ]
},
{
    "id": "32ae2dc5.59e942",
    "type": "hmac",
    "z": "1fee60dc.191fff",S
    "name": "",
    "algorithm": "HmacSHA512",
    "key": "Enter-HMAC-Key-Here",
    "x": 130,
    "y": 140,
    "wires": [
        [
            "ab57849c.aa3bc8"
        ]
    ]
}
]

Open the hmac node by double clicking it. Enter a secret key to encrypt passwords. This key should be the same as the one in the Credentials flow (more on that).

Control

For the flow that will control the GPIOs, paste the following into a new flow.

[
{
    "id": "df1c684d.9cb458",
    "type": "websocket in",
    "z": "ce96cab0.f0ae38",
    "name": "",
    "server": "ded96095.9ca83",
    "client": "",
    "x": 130,
    "y": 160,
    "wires": [
        [
            "b0e47c94.e6633"
        ]
    ]
},
{
    "id": "b0e47c94.e6633",
    "type": "json",
    "z": "ce96cab0.f0ae38",
    "name": "",
    "x": 290,
    "y": 160,
    "wires": [
        [
            "c6623a05.7892f8"
        ]
    ]
},
{
    "id": "c6623a05.7892f8",
    "type": "function",
    "z": "ce96cab0.f0ae38",
    "name": "",
    "func": "var m = msg.payload;\n\nvar dmv = context.global.get('dmv')||{};\nvar license = m.License;\nvar now = (new Date()).getTime();\nif(dmv[license] + 300000 < now){\n    msg.payload = \"Connection Timeout\";\n    return [null, null, null, null, msg];\n}\n\nvar thrust = 'Idle';\nvar yaw = 'Straight';\n\nif(m.Forward == 1 && m.Reverse == 1){\n    m.Forward = 0;\n    m.reverse = 0;\n}\nif(m.Left == 1 && m.Right == 1){\n    m.Right = 0;\n    m.Left = 0;\n}\nif(m.Forward == 1){thrust = 'Forward';}\nif(m.Reverse == 1){thrust = 'Reverse';}\nif(m.Left == 1){yaw = 'Left';}\nif(m.Right == 1){yaw = 'Right';}\n\nvar text = thrust + ' ' + yaw;\n\nreturn [{payload: m.Forward},\n        {payload: m.Reverse},\n        {payload: m.Left},\n        {payload: m.Right},\n        {payload: text}];",
    "outputs": "5",
    "noerr": 0,
    "x": 410,
    "y": 160,
    "wires": [
        [
            "c7ca048b.847218"
        ],
        [
            "eea3a4ae.fa6728"
        ],
        [
            "5ae351ad.5a538"
        ],
        [
            "575f8ccf.7c4274"
        ],
        [
            "45ffa258.57e9cc"
        ]
    ]
},
{
    "id": "45ffa258.57e9cc",
    "type": "websocket out",
    "z": "ce96cab0.f0ae38",
    "name": "",
    "server": "ded96095.9ca83",
    "client": "",
    "x": 560,
    "y": 280,
    "wires": []
},
{
    "id": "c7ca048b.847218",
    "type": "rpi-gpio out",
    "z": "ce96cab0.f0ae38",
    "name": "PIN: 35 - Forward",
    "pin": "35",
    "set": true,
    "level": "0",
    "freq": "",
    "out": "out",
    "x": 570,
    "y": 40,
    "wires": []
},
{
    "id": "5ae351ad.5a538",
    "type": "rpi-gpio out",
    "z": "ce96cab0.f0ae38",
    "name": "PIN: 38 - Left",
    "pin": "38",
    "set": true,
    "level": "0",
    "freq": "",
    "out": "out",
    "x": 570,
    "y": 160,
    "wires": []
},
{
    "id": "eea3a4ae.fa6728",
    "type": "rpi-gpio out",
    "z": "ce96cab0.f0ae38",
    "name": "PIN: 37 - Reverse",
    "pin": "37",
    "set": true,
    "level": "0",
    "freq": "",
    "out": "out",
    "x": 610,
    "y": 100,
    "wires": []
},
{
    "id": "575f8ccf.7c4274",
    "type": "rpi-gpio out",
    "z": "ce96cab0.f0ae38",
    "name": "PIN: 36 - Right",
    "pin": "36",
    "set": true,
    "level": "0",
    "freq": "",
    "out": "out",
    "x": 600,
    "y": 220,
    "wires": []
},
{
    "id": "ded96095.9ca83",
    "type": "websocket-listener",
    "z": "ce96cab0.f0ae38",
    "path": "/ws/picar",
    "wholemsg": "false"
}
]

Note the pins use for controling the car. Top to bottom they are: 35-forward, 37-reverse, 38-left, 36-right. Use these pins when connecting the Pi to the RC car receiver (more on that).

Credentials

Paste the following into a new flow. This flow will allow the creation of username & password combinations with the secret key.

[
{
    "id": "4f0d436a.ec82ac",
    "type": "function",
    "z": "c737272f.d855b8",
    "name": "Get Submitted",
    "func": "msg.driver= msg.payload.driver;\nvar keyobject = {};\nkeyobject[msg.driver] = msg.payload.key;\nmsg.payload = JSON.stringify(keyobject);\nreturn msg;",
    "outputs": 1,
    "noerr": 0,
    "x": 160,
    "y": 100,
    "wires": [
        [
            "8c74f440.f638a8"
        ]
    ]
},
{
    "id": "b33337a3.31d4d8",
    "type": "function",
    "z": "c737272f.d855b8",
    "name": "Save Cred",
    "func": "var driver = msg.driver;\nvar key = msg.key;\n\nvar keyring = msg.payload || {};\nkeyring[driver] = key;\n\nmsg.payload = JSON.stringify(keyring);\nreturn msg;",
    "outputs": "1",
    "noerr": 0,
    "x": 410,
    "y": 180,
    "wires": [
        [
            "d07d1ae3.8f6b68"
        ]
    ]
},
{
    "id": "d07d1ae3.8f6b68",
    "type": "file",
    "z": "c737272f.d855b8",
    "name": "Put keys",
    "filename": "/home/pi/.picar/www/keys",
    "appendNewline": true,
    "createDir": false,
    "overwriteFile": "true",
    "x": 400,
    "y": 220,
    "wires": []
},
{
    "id": "be908f37.6b4ce",
    "type": "file in",
    "z": "c737272f.d855b8",
    "name": "Get keys",
    "filename": "/home/pi/.picar/www/keys",
    "format": "utf8",
    "sendError": true,
    "x": 400,
    "y": 100,
    "wires": [
        [
            "d2df6932.934d08"
        ]
    ]
},
{
    "id": "d2df6932.934d08",
    "type": "json",
    "z": "c737272f.d855b8",
    "name": "",
    "x": 390,
    "y": 140,
    "wires": [
        [
            "b33337a3.31d4d8"
        ]
    ]
},
{
    "id": "8a376d0d.b18bf",
    "type": "inject",
    "z": "c737272f.d855b8",
    "name": "New Driver",
    "topic": "",
    "payload": "{\"driver\":\"\", \"key\":\"\"}",
    "payloadType": "json",
    "repeat": "",
    "crontab": "",
    "once": false,
    "x": 140,
    "y": 60,
    "wires": [
        [
            "4f0d436a.ec82ac"
        ]
    ]
},
{
    "id": "f0dd55f9.38ace8",
    "type": "function",
    "z": "c737272f.d855b8",
    "name": "Get Cred",
    "func": "msg.key = msg.payload;\nreturn msg;",
    "outputs": 1,
    "noerr": 0,
    "x": 140,
    "y": 180,
    "wires": [
        [
            "c2927ec8.d2996"
        ]
    ]
},
{
    "id": "c2927ec8.d2996",
    "type": "function",
    "z": "c737272f.d855b8",
    "name": "keys Exists",
    "func": "if(!msg.payload){\n    return [{payload:'{}'}, null]\n}\nreturn [null, msg];",
    "outputs": "2",
    "noerr": 0,
    "x": 150,
    "y": 220,
    "wires": [
        [
            "761b678e.1e1158"
        ],
        [
            "be908f37.6b4ce"
        ]
    ]
},
{
    "id": "761b678e.1e1158",
    "type": "file",
    "z": "c737272f.d855b8",
    "name": "Make keys",
    "filename": "/home/pi/.picar/www/keys",
    "appendNewline": true,
    "createDir": false,
    "overwriteFile": "false",
    "x": 390,
    "y": 60,
    "wires": []
},
{
    "id": "8c74f440.f638a8",
    "type": "hmac",
    "z": "c737272f.d855b8",
    "name": "",
    "algorithm": "HmacSHA512",
    "key": "The-same-secret-key-from-the-webserver-flow",
    "x": 130,
    "y": 140,
    "wires": [
        [
            "f0dd55f9.38ace8"
        ]
    ]
}
]

Again open the hmac node by double clicking it. Enter the same secret key you used in the Web Server flow.

To create a new driver from this screen open the New Driver node by double clicking it. Edit the payload with the desired credentials.

{"driver":"enter-user-name", "key":"enter-password"}

Click Done and then Deploy. Once the flow is deployed click the box on the left of the New Driver node to inject the credentials. The username and a hash of the password will be added to the "keys" file. You can now log into the page with those credentials. Any additional times this is done adds a new user. If a username is reused it should update that user. To delete a user open the "keys" file in /home/pi/.picar/www/ and delete that entry. I hope to come up with a better solution for that in the future.

View the results

Point a browser to the root of the Pi's webserver on port 1880. http://ip_address:1880/picar . If everything has gone according to the plan the PiCar webpage should be visible. There will be no video for the webcam because that has not been setup. If the direction buttons are pressed the Pi should respond by updating the direction text.