GertDuino Getting Started Tutorial – Hello World

In my Introduction to the GertDuino I explained how it allows the Pi to compile and send code to an Atmega328 micro-controller. In this post I will explain the steps you need to take to get it up and running with an example program called “blink”.

The example is fairly basic and turns on the onboard blue LEDs. Once completed you will have a working system ready for your own experiments. When I started I had never used an Arduino so hopefully this post will help simplify some of things that confused me when I took the board out of the box.

Initial Setup

Before connecting your GertDuino board to the Pi you need to make a small change to the config.txt file on your SD card. Without this tweak the GD board will cause the Pi boot into safe mode as it grounds Pin 5. This doesn’t help at all so it’s best to disable it before we start.

Add the following to your config.txt file (which is in the /boot/ directory) :

avoid_safe_mode=1

You can use any text editor you prefer but to do it using nano type :

sudo nano config.txt

Add the line and then quit using CTRL-X, Y then ENTER.

Shutdown the Pi using :

sudo halt

When it has finished shutting down remove the power supply.

Prepare The Board

In order to program the board from the Pi we need to add four jumpers. Once these are in place connect the board to the Pi GPIO header. The rubber bumper should rest on the USB port giving the board some support.

You can now reattach the power to the Pi and let it boot up. Once you have logged in and you can see the command prompt we are ready to continue.

Install Software

First we need to install a cross-compiler. This will allow the Pi to compile code which can be run on the Atmega devices.

sudo apt-get update
sudo apt-get install arduino

The update step is important as it ensures the latest Arduino package is installed. This may take 5 minutes so go grab a coffee/tea/water/IrnBru.

Next we need a program called “avrdude” which will allow us to load the code into the Atmega devices. Gordon Henderson (projects.drogon.net) has created a modified version which allows us to make use of the Pi’s GPIO pins for the transfer :

cd /tmp
wget http://project-downloads.drogon.net/gertboard/avrdude_5.10-4_armhf.deb
sudo dpkg -i avrdude_5.10-4_armhf.deb
sudo chmod 4755 /usr/bin/avrdude

Initial Device Setup

Before using the board for the first time we need to setup the Atmega328 to use the external 16MHz crystal :

avrdude -qq -c gpio -p atmega328p -U lock:w:0x3F:m -U efuse:w:0x07:m -U lfuse:w:0xE7:m -U hfuse:w:0xD9:m

If you didn’t understand all the details in the line above then welcome to the club! It’s one of those commands you’ll have to just run and worry about another time. If you’ve forgotten to add the four jumpers you’ll get an error message.

Download Examples

The last step is to grab some example files. In this case we will use the files supplied by Element14 on their GertDuino resource page.

cd /home/pi
wget http://www.element14.com/community/servlet/JiveServlet/downloadBody/64547-102-2-287143/gertduino.zip
unzip gertduino.zip

The files will be extracted to a directory named “gertduino”. We can now open this directory to find the source code (blink.c) and compiled hex file (blink.hex).

cd gertduino
cd blink

The hex file for this has already been created but you can use the “make” command to re-compile it :

make

You will need to do this for your own source code or if you modify the blink.c file. To tranfer the hex file to the Atmega we are going to use a program called “program_328”. This application is already included in this directory but we need to make it executable by tweaking its permissions :

chmod 777 program_328

Finally we can send the blink hex file to the Atmega 328 chip by using :

./program_328 blink.hex

You should see an output similar to that below :

avrdude: AVR device initialized and ready to accept instructions

Reading | ############################################ | 100% 0.00s

avrdude: Device signature = 0x1e950f
avrdude: NOTE: FLASH memory has been specified,
         an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "blink.hex"
avrdude: input file blink.hex auto detected as Intel Hex
avrdude: writing flash (594 bytes):

Writing | ############################################ | 100% 0.34s

avrdude: 594 bytes of flash written
avrdude: verifying flash memory against blink.hex:
avrdude: load data flash data from input file blink.hex:
avrdude: input file blink.hex auto detected as Intel Hex
avrdude: input file blink.hex contains 594 bytes
avrdude: reading on-chip flash data:

Reading | ############################################ | 100% 0.32s

avrdude: verifying ...
avrdude: 594 bytes of flash verified

avrdude: safemode: Fuses OK

avrdude done.  Thank you.

If everything has gone to plan the six blue LEDs on the GertDuino board should be turning on and off in sequence.

Your first steps in Pi-Arduino fun is complete, congratulations!