Sure, TJBot can't walk but there are other ways to be mobile.

This project will give TJBot the ability to control an RC truck to provide mobility. It uses an inexpensive RC vehicle as some hardware modifications are required and one might not want to open the covers on an expense device.

A soldering iron and some basic electronic experience will help with this project but with care this can be done as a first experience with both.

For this project a wireless headset is recommended rather than the simple USB microphone as noise from the vehicle can interfere with the voice commends. In the video below a wireless headset was used.

You can also use a wired headset if you don't mind having to stay close to the vehicle.

1. TJBot
2. A suitable RC vehicle (ones that use two 1.5 volt batteries are preferred)
3. Soldering iron and solder
4. Several proto-board jumpers (one end will be cut off)
5. Wireless headset (suggested, rather than simple USB microphone)

Once you have the RC vehicle you can look inside the controller to gain a better understanding of what else is needed to connect it to the Raspberry Pi in the TJBot.

The software and scripts assume the software is installed in /opt, a standard directory for "optional" software. To install the software use

sudo sh -c 'cd /opt ; git clone https://github.com/pgcrumley/Projects.git'

This will place a copy of the software in /opt and leave behind information that makes it easy to retrieve updates later if needed.

Next

cd /opt/Projects/TJBot_Drives/

and make sure there are a number of python and other scripts present.

Install python3 and the RPi.GPIO library using a command of:

sudo apt-get -y install python3 python3-dev git python3-rpi.gpio

Make sure python3 works and RPi.GPIO is installed by typing:

python3
import RPi.GPIO
exit()

Your console should look like this:

$ python3
Python 3.4.2 (default, Oct 19 2014, 13:31:11)
[GCC 4.9.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import RPi.GPIO
>>> exit()
$

The version numbers may vary but there should not be any messages after the import RPi.GPIO line.

This step will require soldering ability and you will void any warranty on the RC device. If you need help with soldering I would refer you to some soldering advice for more information.

Many of the simple controllers will use buttons or switches in the controller which connect a signal to ground in order to activate a particular function. The controller for the vehicle used here has 4 switches for the functions of:

1. Right-side Forward
2. Left-side Forward
3. Right-side Backward
4. Left-side Backward

With a bit of inspection you should be able to find where to attach to the transmitter board if you use a different vehicle.

Pigtails are connected to each of these signals so they can be pulled low by the Raspberry Pi. We will also connect a pigtail to ground and power so the transmitter is powered by the Raspberry Pi rather than by batteries.

The first thing to do is prepare the pigtails so it is easy to attach them to the board in the RC transmitter. Cut off one end and expose a short amount of the wire inside (about 2 mm). Apply solder to the end of the wire so it is ready to attach with just heat.

For this project the pigtails look like this: (there will also be a pigtail attached to the positive battery terminal)

Cut a slot for the pigtails to come out of the case. The result should look something like this:

Once the pigtails are outside of the case it would be good to put batteries in the controller to make voltage and current measurements of the pins to ensure the voltage will not be larger than 3.3 volts and the current when the signal is connected to ground is lower than the capabilities of the Raspberry Pi.

Here we see the voltage is under 3.3 volts (as we expected since this is powered by two 1.5 volt batteries) and the current is about 2.8 mA which is no problem for the Raspberry Pi.

Remove the batteries so you do not have the batteries competing with the Raspberry Pi voltage supplies.

Depending on the length of pigtail you used, it might be easier to extend the pigtails with some Male - Female proto-board jumper wires.

Note: For this project the servo motor data connection will move from Raspberry Pi GPIO 7 on board pin 26 to GPIO 12 on board pin 32.

This is needed because the 4 signal pins needed for the vehicle should all be in the HIGH state when the Raspbery Pi is first turned on so the
vehicle is stationary. Few pins are in the HIGH state when power is applied and the original servo pin is one of those special pins. We move to a new pin to accomodate this need.

Code in the node program will tell TJBot about the new location of the servo signal. Start by connecting just the 3.3 volt power and ground pigtails to the Raspberry Pi. I would recommend using Raspberry Pi pins 17 and 25. Please note these are board numbers, not GPIO numbers.

With the RC transmitter powered from the Raspberry Pi make sure the normal controls still properly operate the vehicle. Once you are sure the transmitter still works correctly is it time to attach the pigtails for the other signals.

The signal to pin connections are:

Run the driver_controller program to make sure the pigtails are connected properly. Make sure the vehicle has plenty of space to drive and run

sudo driver_controller.py

By default this command will drive:

1. forward for 1 second
2. left for 1 second
3. clockwise for 2 seconds
4. counter-clockwise for 2 seconds
5. backward for 1 second
6. right for 1 second

You can use this program to control the vehicle.

sudo driver_controller.py --help

gives more details.

Once you have this working you are ready to have TJBot drive.

The TJBot program uses a REST server to control the vehicle. TO have that server configured to start automatically each time the system is started.

As root:

cd /opt/Projects/TJBot_Drives

To do this a configuration file is copied to the /lib/systemd/system directory then the service is enabled to start automatically. You can also start the service immediately without rebooting the system.

To set up the facility use

cp tjbot_rest_server.service /lib/systemd/system
systemctl enable driver_rest_server

You can start the service without rebooting by typing

systemctl start driver_rest_server

Finally, you can check the status of the service with

systemctl status driver_rest_server

This last command should provide out similar to

o  driver_rest_server.service - Run REST server for TOYDALOO RC dump truck controller
    Loaded: loaded (/lib/systemd/system/driver_rest_server.service; enabled; vendor preset: enabled)
    Active: active (running) since Mon 2018-01-01 22:31:22 EST; 4min 57s ago
  Main PID: 1245 (python3)
    CGroup: /system.slice/driver_rest_server.service
            \-1245 python3 /opt/Projects/TJBot_Drives/driver_rest_server.py

Jan 01 22:31:22 tjbot systemd[1]: Started Run REST server for TOYDALOO RC dump truck controller.

You can now make the vehicle spin clock-wise with this command:

curl -H 'Content-Type: application/json' -X POST -d '{"drive_ops" : [ ["cw", 1] ]}'  http://localhost:9999/

Notice the above command does not need the sudo command. You do not need root access to send the REST commands to the server. This allows many programs to share the devices.

By default the REST server only responds to requests which are sent from the same host but you can change the way the server is started by altering the StartExec line in the .service file so any host on your network can send a REST command. To do this add --network_address 0.0.0.0 to the end of the command and restart.

Create a config.js file which holds your IBM Bluemix credintials for the speech-to-text function. This can be the same file as you used with the speech-to-text project in the normal TJBot recipe.

In addition to the credential information you need to add two additional pieces of information to the config.js file which give the IP address of the REST server which sends appropriate signals to the RC transmitter.

// Create the credentials object for export
exports.credentials = {};

// Watson Speech to Text
// https://www.ibm.com/watson/developercloud/speech-to-text.html
exports.credentials.speech_to_text = {
    username: 'xxxxxxxxxxxxxxxxxx',
    password: 'xxxxxxxx'
}

exports.drive_server_address = "127.0.0.1"; // by default use "localhost"
exports.drive_server_port = 9999;  // by default use IP port 9999

Run

sudo npm install

to prepare the node.js environment. This will take some time.

Now it is time to put your TJBot to work controlling devices. Start the program with

sudo node drive.js

After a few seconds TJBot will be ready for a command.
The program is listening for drive commands of "forward", "backward", "stop", "right", "left", "clock-wise", "counter-clock-wise".

If you have trouble with this project, first make sure the RC controller is able to control the vehicle. After that make sure the REST server is running.