Programming an Arduino with C and a command line.
The Arduino IDE is the most convenient way to get started with Arduino, but it does obscure the underlying mechanics of building software for an Arduino.
How to do it from scratch?
I use a Mac and homebrew, so what follows is a MacOSX-specific guide to building software for an Arduino from the command line. I'm using a few posts from the net as my guide, in particular Setting up AVR-GCC Toolchain on Linux and Mac OS X from maxembedded.
Installing avr-libc actually pulls in avr-gcc and avr-binutils.
brew tap osx-cross/avr
brew install avr-libc
brew install avrdude --with-usb
$ which avr-gcc
/usr/local/bin/avr-gcc
$ avr-gcc --version
avr-gcc (GCC) 4.9.3
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ which avrdude
/usr/local/bin/avrdude
$ avrdude -?
Usage: avrdude [options]
[...]
avrdude version 6.3, URL: <http://savannah.nongnu.org/projects/avrdude/>
All good to go!
Use avr-lib to compile and generate the Intel Hex format file.
Source is blinky/blinky.c and is written for an atmega328p/Arduino Uno.
$ cd blinky
$ avr-gcc -w -Os -Wl,--gc-sections -DF_CPU=16000000UL -mmcu=atmega328p -c blinky.c
$ avr-gcc -mmcu=atmega328p blinky.o -o blinky.elf
$ avr-objcopy -j .text -j .data -O ihex blinky.elf blinky.hex
I have an Arduino connected to the USB and appearing on /dev/cu.usbmodem14541. Use avrdude to flash it with some options:
-D: disable auto erase for flash-v: verbose output-c arduino: specify the programmer to be used-p atmega328p-P /dev/cu.usbmodem14541: port-b 115200: baud rate-U flash:w:blinky.hex:i: Perform a memory operation:flash: memtype is flash ROMw: read the specified file (blinky.hex) and write it to flash (memtype)i: specify the file is Intel Hex format
$ avrdude -D -v -c arduino -p atmega328p -P /dev/cu.usbmodem14541 -b 115200 -U flash:w:blinky.hex:i
avrdude: Version 6.3, compiled on Mar 15 2016 at 21:26:45
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "/usr/local/Cellar/avrdude/6.3/etc/avrdude.conf"
User configuration file is "/Users/paulgallagher/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/cu.usbmodem14541
Using Programmer : arduino
Overriding Baud Rate : 115200
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 : Arduino
Description : Arduino
Hardware Version: 3
Firmware Version: 4.4
Vtarget : 0.3 V
Varef : 0.3 V
Oscillator : 28.800 kHz
SCK period : 3.3 us
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: safemode: hfuse reads as 0
avrdude: safemode: efuse reads as 0
avrdude: reading input file "blinky.hex"
avrdude: writing flash (178 bytes):
Writing | ################################################## | 100% 0.04s
avrdude: 178 bytes of flash written
avrdude: verifying flash memory against blinky.hex:
avrdude: load data flash data from input file blinky.hex:
avrdude: input file blinky.hex contains 178 bytes
avrdude: reading on-chip flash data:
Reading | ################################################## | 100% 0.03s
avrdude: verifying ...
avrdude: 178 bytes of flash verified
avrdude: safemode: hfuse reads as 0
avrdude: safemode: efuse reads as 0
avrdude: safemode: Fuses OK (E:00, H:00, L:00)
avrdude done. Thank you.
The commands above are a bit tedious. A simple Makefile automates the process:
$ cd blinky
$ make clean
rm *.o
rm *.elf
rm *.hex
$ make
avr-gcc -w -Os -Wl,--gc-sections -DF_CPU=16000000UL -mmcu=atmega328p -c blinky.c
avr-gcc -mmcu=atmega328p -Wl,-Map,blinky.map blinky.o -o blinky.elf
avr-objcopy -j .text -j .data -O ihex blinky.elf blinky.hex
avr-objdump -h -S blinky.elf > blinky.lst
$ make flash
avrdude -D -v -c arduino -p atmega328p -P /dev/cu.usbmodem14541 -b 115200 -U flash:w:blinky.hex:i
[...]
avrdude done. Thank you.