Arduino from the command line

Update News

The current version of this software (0.4) won't work with versions of the Arduino software before 0018.

Introduction

The Arduino¹ has done much to popularize microcontrollers for the casual tinkerer. Its success suggests that there's considerable value in combining a standard microcontroller (the ATmega) and a GCC based toolchain into an easily digesible package. For myself, it's certainly easier to just install the latest release of the Arduino software than worry about building my own cross-compilers, particularly when it's all new to me and consequently somewhat confusing.

After working through the toy tutorials though, I found myself wishing that writing code for the Arduino were more like writing other C programs. In my case, that means editing it with emacs then building it with make. I must emphasize that I'm not criticizing the Arduino IDE: there's nothing wrong with it beyond it not being emacs...

It turns out that others have been along this path before: the Arduino website has a hopeful sounding Arduino from the Command Line² article. In turn this points you at the Makefile shipped as part of the Arduino software distribution: hardware/cores/arduino/Makefile.

This didn't really fit quite what I wanted to do though, so I wrote my own Makefile. You might wonder why I should embark on such a task. Well:

• I was keen that all of my objects and random other files were completely separate from the main Arduino stuff in the applet directory.
• Although I wanted to be able to build Arduino sketches, I also wanted a suitable jumping-off point for code which didn't use wiring. In other words, to regard the Arduino software as a convenient way to get the AVR GCC toolchain.
• Rather than dumping a big Makefile in each sketch directory, I wanted to have a few definitions in the directory which then included a large project-independent file from elsewhere.

Finally, one of the things I enjoy about writing code for microcontrollers is the sense of continuity between the hardware datasheets published by the chip manufacturer and the code I write (by contrast if you're writing code on Linux there's a vast gulf between the code executing printf and stuff appearing on the screen). Writing my own Makefile seemed a good way to make sure I understood what was going on.

So to the Makefile. Obviously it owes a great debt to the people who wrote the Makefile shipped with the Arduino IDE and here's the credit list from that file:

# Arduino 0011 Makefile                                  
# Arduino adaptation by mellis, eighthave, oli.keller    

Thanks then to mellis, eighthavem and oli.keller.

Installation instructions

You'll need to download the tarball containing the Makefile,³, unpack it, and then copy the Makefile somewhere sensible:

$ wget http://mjo.tc/atelier/2009/02/acli/arduino-mk_0.4.tar.gz 
$ tar xzvf arduino-mk_0.4.tar.gz 
$ cp arduino-mk-0.4/Arduino.mk /path/to/my/arduino/stuff/Arduino.mk 

The next step is to create a small Makefile for the sketch you actually want to build. The typical Arduino sketch directory looks like this:

$ ls -ltr  
total 8    
drwxr-xr-x   4 mjo  staff  136 15 Feb 19:53 applet        
-rw-r--r--@  1 mjo  staff  384 17 Feb 16:11 CLItest.pde

To this we'll add a Makefile:

ARDUINO_DIR = /Applications/Arduino.app/Contents/Resources/Java 
                                            
TARGET       = CLItest                            
MCU          = atmega168                          
F_CPU        = 16000000                           
ARDUINO_PORT = /dev/cu.usb*                       
                                            
ARDUINO_LIBS = LiquidCrystal              
                                            
include /path/to/my/arduino/stuff/Arduino.mk

Hopefully these will be self-explanatory but in case they're not:

ARDUINO_DIR

Where you installed the Arduino software. On the Mac this has to point deep inside the Arduino installation /Applications.

TARGET

The basename used for the final files. Canonically this would match the .pde file, but you can choose anything!

ARDUINO_LIBS

A list of any libraries used by the sketch—we assume these are in $(ARDUINO_DIR)/hardware/libraries.

MCU

The target processor (atmega168 for the Duemilanove).

F_CPU

The target's clock speed (16000000 for the Duemilanove).

ARDUINO_PORT

The port where the Arduino can be found (only needed when uploading) If this expands to several ports, the first will be used.

A couple of other options might be useful:

AVRDUDE_ARD_PROGRAMMER

The protocol avrdude speaks—defaults to stk500v1.

AVRDUDE_ARD_BAUDRATE

The rate at which we talk to the board—defaults to 19,200.

If you're using the toolchain provided by the system rather than bundled with the Arduino software (as I think is the case on Linux) then you'll have to add some more paths:

AVR_TOOLS_PATH   = /usr/bin  
AVRDUDE_CONF     = /etc/avrdude.conf

Building

If you're used to Unix then this is easy:

$ make 
...

The output is pretty verbose, but I think it should be obvious if it worked. After building you'll see a new directory has been created which contains all the object files: build-cli.

$ ls -l  
total 32 
-rw-r--r--@  1 mjo  staff  384 17 Feb 16:11 CLItest.pde  
-rw-r--r--@  1 mjo  staff  202 17 Feb 16:39 Makefile     
drwxr-xr-x   4 mjo  staff  136 15 Feb 19:53 applet       
drwxr-xr-x  21 mjo  staff  714 17 Feb 17:52 build-cli    

build-cli

Let's peek inside the build-cli directory:

$ ls -l build-cli 
total 392 
-rw-r--r--  1 mjo  staff    491 17 Feb 17:52 CLItest.cpp          
-rw-r--r--  1 mjo  staff    583 17 Feb 17:52 CLItest.d            
-rwxr-xr-x  1 mjo  staff  60971 17 Feb 17:52 CLItest.elf          
-rw-r--r--  1 mjo  staff   3994 17 Feb 17:52 CLItest.hex          
-rw-r--r--  1 mjo  staff   5932 17 Feb 17:52 CLItest.o            
-rw-r--r--  1 mjo  staff   6920 17 Feb 17:52 HardwareSerial.o     
-rw-r--r--  1 mjo  staff  12708 17 Feb 17:52 Print.o              
-rw-r--r--  1 mjo  staff   6852 17 Feb 17:52 WInterrupts.o        
-rw-r--r--  1 mjo  staff   4680 17 Feb 17:52 WMath.o              
-rw-r--r--  1 mjo  staff    611 17 Feb 17:52 depends.mk           
-rw-r--r--  1 mjo  staff   5900 17 Feb 17:52 pins_arduino.o       
-rw-r--r--  1 mjo  staff   8476 17 Feb 17:52 wiring.o             
-rw-r--r--  1 mjo  staff   7224 17 Feb 17:52 wiring_analog.o      
-rw-r--r--  1 mjo  staff   8244 17 Feb 17:52 wiring_digital.o     
-rw-r--r--  1 mjo  staff   6544 17 Feb 17:52 wiring_pulse.o       
-rw-r--r--  1 mjo  staff   7424 17 Feb 17:52 wiring_serial.o      
-rw-r--r--  1 mjo  staff   5308 17 Feb 17:52 wiring_shift.o       

Most of the files in here are object files for the wiring library. What about the others ?

CLItest.cpp

This is the .pde sketch file with a small main program prepended and a suitable #include prepended.

CLItest.d

This tracks the dependencies used by CLItest.pde

CLItest.elf

This is executable produced by the linker

CLItest.hex

This is a hex dump of (the code part) of the executable in a format understood by the Arduino's bootloader.

CLItest.o

The object file we got by compiling CLItest.cpp.

depends.mk

A single file containing all the dependency relations (it's the concatentation of all the .d files).

You may recall the TARGET variable we specified in the Makefile above: it's that which sets the base name for e.g. CLItest.elf. However CLItest.cpp, CLItest.o and CLItest.d take their name from the .pde sketch file.

Uploading code

This is easy:

$ make upload

Uploading via ISP

If you're using target hardware which doesn't have a bootloader then you might want to use ISP to upload the code. Though you'll obviously need some extra hardware to do this.

Assuming that avrdude supports your programmer though, you'll only need to make a few changes to the Makefile to tell avrdude where it can find the programmer and how to talk to it:

ISP_PORT         = /dev/ttyACM0 
ISP_PROG         = -c stk500v2

Then to upload:

$ make ispload

Fuses

You might need to change the fuse settings when programming, though some care needs to be taken here or you might irreversibly change the chip. You can set the fuse settings thus (the values below are the defaults):

ISP_LOCK_FUSE_PRE  = 0x3f 
ISP_LOCK_FUSE_POST = 0xcf 
ISP_HIGH_FUSE      = 0xdf 
ISP_LOW_FUSE       = 0xff 
ISP_EXT_FUSE       = 0x01

Growing the project

There a couple of obvious things to do now. You might want to edit the sketch. That's easy: just edit the .pde file and run make again.

Alternatively you might want to add some more source files to the project. That's easy too: the Makefile understands C, C++ and assembler files in the source directory (with .c, .cpp, and .s extensions). Everything should just work.

Wiring-less development

Finally you might want to develop code which isn't linked against the Wiring library. There's some scope for this: just set NO_CORE in the Makefile e.g.

NO_CORE = 1

Bugs and problems

• The Makefile isn't very elegant.
• Handling Arduino libraries isn't very clean. For one thing I'm relying on them being compiled in a compatible way by the Arduino environment which is probably a bit risky. Secondly it's a bit lazy to get the user to specify which libraries are being used manually.
• When compiling the sketch file, the compiler actually sees the .cpp file derived from it. Accordingly the line numbers of any errors will be wrong (but not by that much).
• I fear that the Makefile makes unwarranted assumptions about the hardware: for example, all my Arduino experience has been ATmega 168 related.
• The Makefile doesn't do some of the things that the Makefile distributed with the Arduino software does e.g. generating COFF files. I worry that some of these might be important.
• This hasn't been used very much yet, even by me. I'm writing this now as much for my benefit as anyone else's, though I'd be delighted to know if anyone else finds it useful.

Changelog

2010-05-21, version 0.3

• Tidied up the licensing, making it clear that it's released under LGPL 2.1.
• Philip Hands⁴ sent me some code to reset the Arduino by dropping DTR for 100ms, and I added it.
• Tweaked the Makefile to handle version 0018 of the Arduino software which now includes main.cpp. Accordingly we don't need to—and indeed must not—add main.cxx to the .pde sketch file. The paths seem to have changed a bit too.

2010-05-24, version 0.4

• Tweaked rules for the reset target on Philip Hands' advice.

Revised by Martin Oldfield on 07 Jun 2010, original version 17 Feb 2009.
Contact: Martin Oldfield, ex-atelier@mjo.tc
This work is available under the Creative Commons Attribution-ShareAlike 3.0 Unported License, or the LGPL version 2.1 or later.