In this tutorial I am going to show you how to program an AVR(ATmega328) and an Arduino UNO using the GPIO on the Raspberry Pi.

Adding an Arduino or an AVR to your projects will give you much greater flexibility.

Hook up the Raspberry Pi to the Arduino UNO or AVR.

The image below shows how to connect a Raspberry Pi 2 and an  Arduino UNO. click the image to make it larger

The image below shows how to hook up an ATmega328 (DIP package) to a Raspberry Pi 2. click the image to make it larger

Install avrdude

Once you have your devices hooked up, it is time to install avrdude. Avrdude is an AVR programmer for Linux, which  allows us to use the GPIO pins on the Raspberry Pi to program an AVR or Arduino.
First you need to install some prerequisites

Now install avrdude from source;

Enable linuxgpio in the avrdude source, make and then install;

No we need to tell avrdude to use the GPIO and we need to let it know what GPIO pins to use. This can be done by editing the config file;

Look for "linuxgpio" and you should see this section;

#programmer
#  id    = "linuxgpio";
#  desc  = "Use the Linux sysfs interface to bitbang GPIO lines";
#  type  = "linuxgpio";
#  reset = ?;
#  sck   = ?;
#  mosi  = ?;
#  miso  = ?;
#;

And change it to this;

programmer
  id    = "linuxgpio";
  desc  = "Use the Linux sysfs interface to bitbang GPIO lines";
  type  = "linuxgpio";
  reset = 4;
  sck   = 11;
  mosi  = 10;
  miso  = 9;
;

If everything is hooked up correctly you should now be about to communicate between the Raspberry Pi and Arduino/AVR.

Time for a quick test;

-c Specify the programer type
-p Part Number. Use atmega328p for the Arduino UNO
-v Verbose output
Below is from a successful test;

avrdude: Version 6.2, compiled on Mar  9 2016 at 11:41:53
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch
         System wide configuration file is "/usr/local/etc/avrdude.conf"
         User configuration file is "/root/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping
         Using Port                    : unknown
         Using Programmer              : linuxgpio
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :
                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00
         Programmer Type : linuxgpio
         Description     : Use the Linux sysfs interface to bitbang GPIO lines
         Pin assignment  : /sys/class/gpio/gpio{n}
           RESET   =  4
           SCK     =  11
           MOSI    =  10
           MISO    =  9
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: safemode: hfuse reads as DE
avrdude: safemode: efuse reads as FD
avrdude: safemode: hfuse reads as DE
avrdude: safemode: efuse reads as FD
avrdude: safemode: Fuses OK (E:FD, H:DE, L:FF)
avrdude done.  Thank you.

Blink Example using Arduino IDE

It's time to upload our first sketch.

First, install the Arduino IDE;

Open the arduino IDE and then we need to make one change before we do anything else.  Go the File menu and select Preferences. In  the preference dialog box, place a tick in the 'Show verbose output during compilation'

Now we can load the Blink sketch from the examples folder. The will cause the LED on pin 13 to blink.

Now compile the sketch.

As we have enabled verbose output we can now see what the IDE is doing when it compiles and where it puts the files.

The file that we need to upload to the Arduino/AVR is the .hex file, I have underlined this in the example below.

We will use avrdude to upload the file;

Blink example without Arduino IDE

You can create and compile sketches without the Arduino IDE by using the Arduino Make file. This allows you to edit the code in your favorite text editor and compilation is a lot faster.  This is the method I use.
You still need to install the Arduino IDE as shown above.

Install Arduino makefile

We will now create another blink example however we will use the arduino Makefile to compile our code.

Copy in entire contents from the blink.ino example.

Now we need to create a Makefile that will reference the Arduino Makefile.

And add

include /usr/share/arduino/Arduino.mk

Then compile the blink.ino example

Make will create another folder called build-uno This is where it places the .hex file which we need to upload to the Arduino/AVR.
To upload this hex file;

I put both make and the avrdude commands in the one line, so it will compile the code and then upload right aftwards.

You will notice that it defaults to the board UNO. This can be changed in the Makefile we created. Here you would enter anything different from the defaults.
The below make file would be used for an ATmega1284p running at 20Mhz

MCU = atmega1284p
F_CPU=20000000L
include /usr/share/arduino/Arduino.mk

Read through /usr/share/arduino/Arduino.mk for other options that can be set. The file is very well documented.

References

Compiling Arduino sketches using Makefile
Arduino Makefile on github
Arduino Makefile on Hackaday.com
Arduino from the command line #1
Arduino from the command line #2

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