Raspberry UART – No screen or network needed! WOOT!

My USB to UART bridge adapter arrived today all the way from China. I have been wanting one of these ever since turning up to a raspberry jam to discover they didnt have any more screens left and their network was overloaded meaning i had no way to control my Pi.

 

So after some research I disovered the raspberry pi supported a serial connection (UART) to control the console. I ordered this device which took 1-2 weeks to arrive (£1.65 so can’t complain…)

I wired it up with

  • +5v to pin 2 (optional see below)
  • GND to pin 6
  • RXD to pin 8
  • TXD to pin 10

I then grabbed the driver for it (windows does not auto find a driver) from Silicon Labs

After installing the driver, I opened up device manager, drilled down to Ports (COM & LPT) and found the COM port it was on (COM4 for me).

Now we have all the info we needed, I opened putty up, clicked serial circle tickbox and entered my COM port. Finally I entered the correct speed for the Pi (115200), clicked open and hit enter and I had a login prompt!

Much cheaper than a screen or a router and perfect for Raspberry Jams!

As normal, any questions? Leave them below

Lego PiBot

 Outdated. Check out updated version revision 0.2! http://pi.gbaman.info/?p=97

Lego Pibot

I would like to start off by saying, I didn’t come up with all this myself, I have followed a few guides over the internet to make this and added a bit of my own stuff to it. The guide I used the most was

http://pdwhomeautomation.blogspot.co.uk/2012/11/raspberry-pi-powered-lego-car.html

You will need

  • A Raspberry Pi + SD card
  • A Motor controller

Motor controller

  • A Wifi dongle

USB wifi reciever

  • A battery for the Pi

Old Iphone battery

  • A 9v battery
  • 2 motors
  • Female to female jumper cables
  • Male to male jumper cables
  • Android phone – rooted

Optional

  • Webcam
  • Mobile tablet/Laptop for viewing video feed
  • Mifi portable wifi transmitter

First you will need some sort of base robot to be building this all on, I will only cover the electronics and the software, not how to build your robot.

So here’s my base robot

Lego PiBot Lid

Lego PiBot no lid

It looks a little ugly, but was built to a deadline so I don’t really mind, it works.

So after you have got everything on shopping list, its time to start building!

My lego robot base is built from an old lego RCX box set so I decided to try and use some of the old 9v lego motors.

Lego 9v motor

These motors required gearing to provide enough torque to move the robot forward so if using these motors, keep that in mind. I did come across another problem with these motors, they don’t easily connect to normal wires…

So I cut one of their cables and soldered it to 2 jumper cables and bam!

My custom lego cable

So now we have our motors, we need to hook our motor controller up to the raspberry pi. For this, I recommend you check out the diagram from Paul Geek Dads blog as it is the one I used.

This is Paul Geek Dads blog’s work, all rights to it belong to him

http://1.bp.blogspot.com/-9B_G4M3GpBg/ULPdXXEGmiI/AAAAAAAAAW8/wok_-x_rM_g/s1600/nfm_260920100002.jpg

For my setup I found that a 9v battery would run out very quickly so I got x2 triple AA battery holders to produce that required 9v

Batteries!

So now we have our Raspberry Pi hooked up to our motor controller and our motor controller powered by a 9v battery or some AAs.

Check out the below pictures for pictures on where everything goes

Electronics Electronics Electronics

Note the Pi ground and the black end of the batteries cable both go into GND
Note the Pi ground and the black end of the batteries cable both go into GND

Now time for the software behind it all. I am using Rasbian. At the time of writing, 2012-12-16-wheezy-raspbian. Rasbian comes with WiringPi which is needed for our scripts, if you don’t have it, try sudo apt-get wiringpi

For this section, that is all you need (for attaching a webcam, you will need a little more software but we will get onto that later)

Hook your pi up to a screen and with your wifi dongle plugged in, type startx and open the wifi config on the desktop. Connect to your home wifi. Now that this is done, it should automatically connect to the wifi even without a screen plugged in (seeing as the PiBot does not have a screen….Yet).

The Raspberry Pi

Next, on a windows computer, grab putty

http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

Or if on Mac OS or Linux, open terminal and type

ssh pi@IP address

E.g.        ssh pi@192.168.1.1

Now we are connected, you will need to grab this python script and upload it onto the pi

Use sudo apt-get git

and git clone git://github.com/gbaman/Lego-PiBot.git

To grab the script for the pi. Now you have the scripts, it’s time to move on to the phone.

The Phone

You will need a rooted android phone which can run sl4a http://code.google.com/p/android-scripting/

To grab it just scan the qr codes on the pages below.

SL4A – http://code.google.com/p/android-scripting/

Python interpreter  – http://code.google.com/p/android-scripting/downloads/detail?name=PythonForAndroid_r4.apk&can=2&q=&sort=downloadcount

This great piece of software allows you to install interpreters on your android rooted device (e.g. python interpreter).

Next find a way to get the script onto your phone (different for all phones).

Now you need to set the IP address of your Pi in the scripts. In the android script it is on line 12, UDP_IP =

And on the Pi script it is on line 25, UDP_IP =

Now all you have to do is tap the script and click the command-line button and run the Pi script (sudo python pi_script.py) to run it and move your phone around and your robot should move!

 

Live video! (Optional)

Wouldn’t it be even cooler if you could see what your robot sees as you drive it around? We you can!

I recommend following this guide below, it is very good and explains exactly how to do it.

http://wolfpaulus.com/journal/embedded/raspberrypi_webcam

After following the guide, open up the web page on a smartphone, maybe a tablet or a laptop etc and you can now watch your robot take over the world!

Troubleshooting

If it does not work there is a few things that could have gone wrong.

First test if your Pi is able to turn control the motors. Inside the Pi folder that you grabbed off github, there is a testing_motor1.py and testing_motor2.py. Try running these and see if the motors come on. If not, check the light is on on the motor controller, if not, check back to the pictures for wiring or maybe your board is broken?

If those scripts work then your phone isn’t able to talk to the Pi… Make sure the IP address is right (use ifconfig on the pi) and maybe try rebooting your Pi and phone just in case.

If it still isn’t working, leave a comment below and I may be able to help out.

 

Any question? Leave them below and I will try to answer them the best I can.