Provided by: avr-libc_2.0.0+Atmel3.6.1-2_all bug

NAME

       demo_project

SYNOPSIS

Detailed Description

       At this point, you should have the GNU tools configured, built, and installed on your
       system. In this chapter, we present a simple example of using the GNU tools in an AVR
       project. After reading this chapter, you should have a better feel as to how the tools are
       used and how a Makefile can be configured.

The Project

       This project will use the pulse-width modulator (PWM) to ramp an LED on and off every two
       seconds. An AT90S2313 processor will be used as the controller. The circuit for this
       demonstration is shown in the schematic diagram. If you have a development kit, you should
       be able to use it, rather than build the circuit, for this project.

       Note:
           Meanwhile, the AT90S2313 became obsolete. Either use its successor, the (pin-
           compatible) ATtiny2313 for the project, or perhaps the ATmega8 or one of its
           successors (ATmega48/88/168) which have become quite popular since the original demo
           project had been established. For all these more modern devices, it is no longer
           necessary to use an external crystal for clocking as they ship with the internal 1 MHz
           oscillator enabled, so C1, C2, and Q1 can be omitted. Normally, for this experiment,
           the external circuitry on /RESET (R1, C3) can be omitted as well, leaving only the
           AVR, the LED, the bypass capacitor C4, and perhaps R2. For the ATmega8/48/88/168, use
           PB1 (pin 15 at the DIP-28 package) to connect the LED to. Additionally, this demo has
           been ported to many different other AVRs. The location of the respective OC pin varies
           between different AVRs, and it is mandated by the AVR hardware.

       Schematic of circuit for demo projectSchematic of circuit for demo project

       The source code is given in demo.c. For the sake of this example, create a file called
       demo.c containing this source code. Some of the more important parts of the code are:

       Note [1]:
           As the AVR microcontroller series has been developed during the past years, new
           features have been added over time. Even though the basic concepts of the
           timer/counter1 are still the same as they used to be back in early 2001 when this
           simple demo was written initially, the names of registers and bits have been changed
           slightly to reflect the new features. Also, the port and pin mapping of the output
           compare match 1A (or 1 for older devices) pin which is used to control the LED varies
           between different AVRs. The file iocompat.h tries to abstract between all this
           differences using some preprocessor #ifdef statements, so the actual program itself
           can operate on a common set of symbolic names. The macros defined by that file are:

       · OCR the name of the OCR register used to control the PWM (usually either OCR1 or OCR1A)

       · DDROC the name of the DDR (data direction register) for the OC output

       · OC1 the pin number of the OC1[A] output within its port

       · TIMER1_TOP the TOP value of the timer used for the PWM (1023 for 10-bit PWMs, 255 for
         devices that can only handle an 8-bit PWM)

       · TIMER1_PWM_INIT the initialization bits to be set into control register 1A in order to
         setup 10-bit (or 8-bit) phase and frequency correct PWM mode

       · TIMER1_CLOCKSOURCE the clock bits to set in the respective control register to start the
         PWM timer; usually the timer runs at full CPU clock for 10-bit PWMs, while it runs on a
         prescaled clock for 8-bit PWMs

       Note [2]:
           ISR() is a macro that marks the function as an interrupt routine. In this case, the
           function will get called when timer 1 overflows. Setting up interrupts is explained in
           greater detail in <avr/interrupt.h>: Interrupts.

       Note [3]:
           The PWM is being used in 10-bit mode, so we need a 16-bit variable to remember the
           current value.

       Note [4]:
           This section determines the new value of the PWM.

       Note [5]:
           Here's where the newly computed value is loaded into the PWM register. Since we are in
           an interrupt routine, it is safe to use a 16-bit assignment to the register. Outside
           of an interrupt, the assignment should only be performed with interrupts disabled if
           there's a chance that an interrupt routine could also access this register (or another
           register that uses TEMP), see the appropriate FAQ entry.

       Note [6]:
           This routine gets called after a reset. It initializes the PWM and enables interrupts.

       Note [7]:
           The main loop of the program does nothing -- all the work is done by the interrupt
           routine! The sleep_mode() puts the processor on sleep until the next interrupt, to
           conserve power. Of course, that probably won't be noticable as we are still driving a
           LED, it is merely mentioned here to demonstrate the basic principle.

       Note [8]:
           Early AVR devices saturate their outputs at rather low currents when sourcing current,
           so the LED can be connected directly, the resulting current through the LED will be
           about 15 mA. For modern parts (at least for the ATmega 128), however Atmel has
           drastically increased the IO source capability, so when operating at 5 V Vcc, R2 is
           needed. Its value should be about 150 Ohms. When operating the circuit at 3 V, it can
           still be omitted though.

The Source Code

       /*
        * ----------------------------------------------------------------------------
        * "THE BEER-WARE LICENSE" (Revision 42):
        * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
        * can do whatever you want with this stuff. If we meet some day, and you think
        * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
        * ----------------------------------------------------------------------------
        *
        * Simple AVR demonstration.  Controls a LED that can be directly
        * connected from OC1/OC1A to GND.  The brightness of the LED is
        * controlled with the PWM.  After each period of the PWM, the PWM
        * value is either incremented or decremented, that's all.
        *
        * $Id$
        */

       #include <inttypes.h>
       #include <avr/io.h>
       #include <avr/interrupt.h>
       #include <avr/sleep.h>

       #include "iocompat.h"        /* Note [1] */

       enum { UP, DOWN };

       ISR (TIMER1_OVF_vect)       /* Note [2] */
       {
           static uint16_t pwm;    /* Note [3] */
           static uint8_t direction;

           switch (direction)      /* Note [4] */
           {
               case UP:
                   if (++pwm == TIMER1_TOP)
                       direction = DOWN;
                   break;

               case DOWN:
                   if (--pwm == 0)
                       direction = UP;
                   break;
           }

           OCR = pwm;          /* Note [5] */
       }

       void
       ioinit (void)           /* Note [6] */
       {
           /* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
           TCCR1A = TIMER1_PWM_INIT;
           /*
            * Start timer 1.
            *
            * NB: TCCR1A and TCCR1B could actually be the same register, so
            * take care to not clobber it.
            */
           TCCR1B |= TIMER1_CLOCKSOURCE;
           /*
            * Run any device-dependent timer 1 setup hook if present.
            */
       #if defined(TIMER1_SETUP_HOOK)
           TIMER1_SETUP_HOOK();
       #endif

           /* Set PWM value to 0. */
           OCR = 0;

           /* Enable OC1 as output. */
           DDROC = _BV (OC1);

           /* Enable timer 1 overflow interrupt. */
           TIMSK = _BV (TOIE1);
           sei ();
       }

       int
       main (void)
       {

           ioinit ();

           /* loop forever, the interrupts are doing the rest */

           for (;;)            /* Note [7] */
               sleep_mode();

           return (0);
       }

Compiling and Linking

       This first thing that needs to be done is compile the source. When compiling, the compiler
       needs to know the processor type so the -mmcu option is specified. The -Os option will
       tell the compiler to optimize the code for efficient space usage (at the possible expense
       of code execution speed). The -g is used to embed debug info. The debug info is useful for
       disassemblies and doesn't end up in the .hex files, so I usually specify it. Finally, the
       -c tells the compiler to compile and stop -- don't link. This demo is small enough that we
       could compile and link in one step. However, real-world projects will have several modules
       and will typically need to break up the building of the project into several compiles and
       one link.

           $ avr-gcc -g -Os -mmcu=atmega8 -c demo.c

       The compilation will create a demo.o file. Next we link it into a binary called demo.elf.

           $ avr-gcc -g -mmcu=atmega8 -o demo.elf demo.o

       It is important to specify the MCU type when linking. The compiler uses the -mmcu option
       to choose start-up files and run-time libraries that get linked together. If this option
       isn't specified, the compiler defaults to the 8515 processor environment, which is most
       certainly what you didn't want.

Examining the Object File

       Now we have a binary file. Can we do anything useful with it (besides put it into the
       processor?) The GNU Binutils suite is made up of many useful tools for manipulating object
       files that get generated. One tool is avr-objdump, which takes information from the object
       file and displays it in many useful ways. Typing the command by itself will cause it to
       list out its options.

       For instance, to get a feel of the application's size, the -h option can be used. The
       output of this option shows how much space is used in each of the sections (the .stab and
       .stabstr sections hold the debugging information and won't make it into the ROM file).

       An even more useful option is -S. This option disassembles the binary file and
       intersperses the source code in the output! This method is much better, in my opinion,
       than using the -S with the compiler because this listing includes routines from the
       libraries and the vector table contents. Also, all the 'fix-ups' have been satisfied. In
       other words, the listing generated by this option reflects the actual code that the
       processor will run.

           $ avr-objdump -h -S demo.elf > demo.lst

       Here's the output as saved in the demo.lst file:

       demo.elf:     file format elf32-avr

       Sections:
       Idx Name          Size      VMA       LMA       File off  Algn
         0 .text         000000d0  00000000  00000000  00000094  2**1
                         CONTENTS, ALLOC, LOAD, READONLY, CODE
         1 .data         00000000  00800060  000000d0  00000164  2**0
                         CONTENTS, ALLOC, LOAD, DATA
         2 .bss          00000003  00800060  00800060  00000164  2**0
                         ALLOC
         3 .stab         0000063c  00000000  00000000  00000164  2**2
                         CONTENTS, READONLY, DEBUGGING
         4 .stabstr      00000d6e  00000000  00000000  000007a0  2**0
                         CONTENTS, READONLY, DEBUGGING
         5 .comment      00000011  00000000  00000000  0000150e  2**0
                         CONTENTS, READONLY

       Disassembly of section .text:

       00000000 <__ctors_end>:
          0:     20 e0          ldi  r18, 0x00 ; 0
          2:     a0 e6          ldi  r26, 0x60 ; 96
          4:     b0 e0          ldi  r27, 0x00 ; 0
          6:     01 c0          rjmp .+2       ; 0xa <.do_clear_bss_start>

       00000008 <.do_clear_bss_loop>:
          8:     1d 92          st   X+, r1

       0000000a <.do_clear_bss_start>:
          a:     a3 36          cpi  r26, 0x63 ; 99
          c:     b2 07          cpc  r27, r18
          e:     e1 f7          brne .-8       ; 0x8 <.do_clear_bss_loop>

       00000010 <__vector_8>:
       #include "iocompat.h"         /* Note [1] */

       enum { UP, DOWN };

       ISR (TIMER1_OVF_vect)         /* Note [2] */
       {
         10:     1f 92          push r1
         12:     0f 92          push r0
         14:     0f b6          in   r0, 0x3f  ; 63
         16:     0f 92          push r0
         18:     11 24          eor  r1, r1
         1a:     2f 93          push r18
         1c:     8f 93          push r24
         1e:     9f 93          push r25
           static uint16_t pwm; /* Note [3] */
           static uint8_t direction;

           switch (direction)        /* Note [4] */
         20:     80 91 62 00    lds  r24, 0x0062    ; 0x800062 <direction.1609>
         24:     88 23          and  r24, r24
         26:     f1 f0          breq .+60      ; 0x64 <__SREG__+0x25>
         28:     81 30          cpi  r24, 0x01 ; 1
         2a:     71 f4          brne .+28      ; 0x48 <__SREG__+0x9>
                   if (++pwm == TIMER1_TOP)
                       direction = DOWN;
                   break;

               case DOWN:
                   if (--pwm == 0)
         2c:     80 91 60 00    lds  r24, 0x0060    ; 0x800060 <_edata>
         30:     90 91 61 00    lds  r25, 0x0061    ; 0x800061 <_edata+0x1>
         34:     01 97          sbiw r24, 0x01 ; 1
         36:     90 93 61 00    sts  0x0061, r25    ; 0x800061 <_edata+0x1>
         3a:     80 93 60 00    sts  0x0060, r24    ; 0x800060 <_edata>
         3e:     00 97          sbiw r24, 0x00 ; 0
         40:     39 f4          brne .+14      ; 0x50 <__SREG__+0x11>
                       direction = UP;
         42:     10 92 62 00    sts  0x0062, r1     ; 0x800062 <direction.1609>
         46:     04 c0          rjmp .+8       ; 0x50 <__SREG__+0x11>
         48:     80 91 60 00    lds  r24, 0x0060    ; 0x800060 <_edata>
         4c:     90 91 61 00    lds  r25, 0x0061    ; 0x800061 <_edata+0x1>
                   break;
           }

           OCR = pwm;           /* Note [5] */
         50:     9b bd          out  0x2b, r25 ; 43
         52:     8a bd          out  0x2a, r24 ; 42
       }
         54:     9f 91          pop  r25
         56:     8f 91          pop  r24
         58:     2f 91          pop  r18
         5a:     0f 90          pop  r0
         5c:     0f be          out  0x3f, r0  ; 63
         5e:     0f 90          pop  r0
         60:     1f 90          pop  r1
         62:     18 95          reti
           static uint8_t direction;

           switch (direction)        /* Note [4] */
           {
               case UP:
                   if (++pwm == TIMER1_TOP)
         64:     80 91 60 00    lds  r24, 0x0060    ; 0x800060 <_edata>
         68:     90 91 61 00    lds  r25, 0x0061    ; 0x800061 <_edata+0x1>
         6c:     01 96          adiw r24, 0x01 ; 1
         6e:     90 93 61 00    sts  0x0061, r25    ; 0x800061 <_edata+0x1>
         72:     80 93 60 00    sts  0x0060, r24    ; 0x800060 <_edata>
         76:     8f 3f          cpi  r24, 0xFF ; 255
         78:     23 e0          ldi  r18, 0x03 ; 3
         7a:     92 07          cpc  r25, r18
         7c:     49 f7          brne .-46      ; 0x50 <__SREG__+0x11>
                       direction = DOWN;
         7e:     21 e0          ldi  r18, 0x01 ; 1
         80:     20 93 62 00    sts  0x0062, r18    ; 0x800062 <direction.1609>
         84:     e5 cf          rjmp .-54      ; 0x50 <__SREG__+0x11>

       00000086 <ioinit>:

       void
       ioinit (void)            /* Note [6] */
       {
           /* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
           TCCR1A = TIMER1_PWM_INIT;
         86:     83 e8          ldi  r24, 0x83 ; 131
         88:     8f bd          out  0x2f, r24 ; 47
            * Start timer 1.
            *
            * NB: TCCR1A and TCCR1B could actually be the same register, so
            * take care to not clobber it.
            */
           TCCR1B |= TIMER1_CLOCKSOURCE;
         8a:     8e b5          in   r24, 0x2e ; 46
         8c:     81 60          ori  r24, 0x01 ; 1
         8e:     8e bd          out  0x2e, r24 ; 46
       #if defined(TIMER1_SETUP_HOOK)
           TIMER1_SETUP_HOOK();
       #endif

           /* Set PWM value to 0. */
           OCR = 0;
         90:     1b bc          out  0x2b, r1  ; 43
         92:     1a bc          out  0x2a, r1  ; 42

           /* Enable OC1 as output. */
           DDROC = _BV (OC1);
         94:     82 e0          ldi  r24, 0x02 ; 2
         96:     87 bb          out  0x17, r24 ; 23

           /* Enable timer 1 overflow interrupt. */
           TIMSK = _BV (TOIE1);
         98:     84 e0          ldi  r24, 0x04 ; 4
         9a:     89 bf          out  0x39, r24 ; 57
           sei ();
         9c:     78 94          sei
         9e:     08 95          ret

       000000a0 <main>:

       void
       ioinit (void)            /* Note [6] */
       {
           /* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
           TCCR1A = TIMER1_PWM_INIT;
         a0:     83 e8          ldi  r24, 0x83 ; 131
         a2:     8f bd          out  0x2f, r24 ; 47
            * Start timer 1.
            *
            * NB: TCCR1A and TCCR1B could actually be the same register, so
            * take care to not clobber it.
            */
           TCCR1B |= TIMER1_CLOCKSOURCE;
         a4:     8e b5          in   r24, 0x2e ; 46
         a6:     81 60          ori  r24, 0x01 ; 1
         a8:     8e bd          out  0x2e, r24 ; 46
       #if defined(TIMER1_SETUP_HOOK)
           TIMER1_SETUP_HOOK();
       #endif

           /* Set PWM value to 0. */
           OCR = 0;
         aa:     1b bc          out  0x2b, r1  ; 43
         ac:     1a bc          out  0x2a, r1  ; 42

           /* Enable OC1 as output. */
           DDROC = _BV (OC1);
         ae:     82 e0          ldi  r24, 0x02 ; 2
         b0:     87 bb          out  0x17, r24 ; 23

           /* Enable timer 1 overflow interrupt. */
           TIMSK = _BV (TOIE1);
         b2:     84 e0          ldi  r24, 0x04 ; 4
         b4:     89 bf          out  0x39, r24 ; 57
           sei ();
         b6:     78 94          sei
           ioinit ();

           /* loop forever, the interrupts are doing the rest */

           for (;;)             /* Note [7] */
               sleep_mode();
         b8:     85 b7          in   r24, 0x35 ; 53
         ba:     80 68          ori  r24, 0x80 ; 128
         bc:     85 bf          out  0x35, r24 ; 53
         be:     88 95          sleep
         c0:     85 b7          in   r24, 0x35 ; 53
         c2:     8f 77          andi r24, 0x7F ; 127
         c4:     85 bf          out  0x35, r24 ; 53
         c6:     f8 cf          rjmp .-16      ; 0xb8 <main+0x18>

       000000c8 <exit>:
         c8:     f8 94          cli
         ca:     00 c0          rjmp .+0       ; 0xcc <_exit>

       000000cc <_exit>:
         cc:     f8 94          cli

       000000ce <__stop_program>:
         ce:     ff cf          rjmp .-2       ; 0xce <__stop_program>

Linker Map Files

       avr-objdump is very useful, but sometimes it's necessary to see information about the link
       that can only be generated by the linker. A map file contains this information. A map file
       is useful for monitoring the sizes of your code and data. It also shows where modules are
       loaded and which modules were loaded from libraries. It is yet another view of your
       application. To get a map file, I usually add -Wl,-Map,demo.map to my link command. Relink
       the application using the following command to generate demo.map (a portion of which is
       shown below).

           $ avr-gcc -g -mmcu=atmega8 -Wl,-Map,demo.map -o demo.elf demo.o

       Some points of interest in the demo.map file are:

       .rela.plt
        *(.rela.plt)

       .text           0x0000000000000000       0xd0
        *(.vectors)
        *(.vectors)
        *(.progmem.gcc*)
                       0x0000000000000000                . = ALIGN (0x2)
                       0x0000000000000000                __trampolines_start = .
        *(.trampolines)
        .trampolines   0x0000000000000000        0x0 linker stubs
        *(.trampolines*)
                       0x0000000000000000                __trampolines_end = .
        *libprintf_flt.a:*(.progmem.data)
        *libc.a:*(.progmem.data)
        *(.progmem*)
                       0x0000000000000000                . = ALIGN (0x2)
        *(.jumptables)
        *(.jumptables*)
        *(.lowtext)
        *(.lowtext*)
                       0x0000000000000000                __ctors_start = .

       The .text segment (where program instructions are stored) starts at location 0x0.

        *(.fini2)
        *(.fini2)
        *(.fini1)
        *(.fini1)
        *(.fini0)
        .fini0         0x00000000000000cc        0x4 /usr/lib/gcc/avr/5.4.0/avr4/libgcc.a(_exit.o)
        *(.fini0)
                       0x00000000000000d0                _etext = .

       .data           0x0000000000800060        0x0 load address 0x00000000000000d0
                       [!provide]                        PROVIDE (__data_start, .)
        *(.data)
        .data          0x0000000000800060        0x0 demo.o
        .data          0x0000000000800060        0x0 /build/avr-libc-IcWZK_/avr-libc-2.0.0+Atmel3.6.1/libc/avr-libc/avr/lib/avr4/exit.o
        .data          0x0000000000800060        0x0 /usr/lib/gcc/avr/5.4.0/avr4/libgcc.a(_exit.o)
        .data          0x0000000000800060        0x0 /usr/lib/gcc/avr/5.4.0/avr4/libgcc.a(_clear_bss.o)
        *(.data*)
        *(.gnu.linkonce.d*)
        *(.rodata)
        *(.rodata*)
        *(.gnu.linkonce.r*)
                       0x0000000000800060                . = ALIGN (0x2)
                       0x0000000000800060                _edata = .
                       [!provide]                        PROVIDE (__data_end, .)

       .bss            0x0000000000800060        0x3
                       0x0000000000800060                PROVIDE (__bss_start, .)
        *(.bss)
        .bss           0x0000000000800060        0x3 demo.o
        .bss           0x0000000000800063        0x0 /build/avr-libc-IcWZK_/avr-libc-2.0.0+Atmel3.6.1/libc/avr-libc/avr/lib/avr4/exit.o
        .bss           0x0000000000800063        0x0 /usr/lib/gcc/avr/5.4.0/avr4/libgcc.a(_exit.o)
        .bss           0x0000000000800063        0x0 /usr/lib/gcc/avr/5.4.0/avr4/libgcc.a(_clear_bss.o)
        *(.bss*)
        *(COMMON)
                       0x0000000000800063                PROVIDE (__bss_end, .)
                       0x00000000000000d0                __data_load_start = LOADADDR (.data)
                       0x00000000000000d0                __data_load_end = (__data_load_start + SIZEOF (.data))

       .noinit         0x0000000000800063        0x0
                       [!provide]                        PROVIDE (__noinit_start, .)
        *(.noinit*)
                       [!provide]                        PROVIDE (__noinit_end, .)
                       0x0000000000800063                _end = .
                       [!provide]                        PROVIDE (__heap_start, .)

       .eeprom         0x0000000000810000        0x0
        *(.eeprom*)
                       0x0000000000810000                __eeprom_end = .

       The last address in the .text segment is location 0x114 ( denoted by _etext ), so the
       instructions use up 276 bytes of FLASH.

       The .data segment (where initialized static variables are stored) starts at location 0x60,
       which is the first address after the register bank on an ATmega8 processor.

       The next available address in the .data segment is also location 0x60, so the application
       has no initialized data.

       The .bss segment (where uninitialized data is stored) starts at location 0x60.

       The next available address in the .bss segment is location 0x63, so the application uses 3
       bytes of uninitialized data.

       The .eeprom segment (where EEPROM variables are stored) starts at location 0x0.

       The next available address in the .eeprom segment is also location 0x0, so there aren't
       any EEPROM variables.

Generating Intel Hex Files

       We have a binary of the application, but how do we get it into the processor? Most (if not
       all) programmers will not accept a GNU executable as an input file, so we need to do a
       little more processing. The next step is to extract portions of the binary and save the
       information into .hex files. The GNU utility that does this is called avr-objcopy.

       The ROM contents can be pulled from our project's binary and put into the file demo.hex
       using the following command:

           $ avr-objcopy -j .text -j .data -O ihex demo.elf demo.hex

       The resulting demo.hex file contains:

       :1000000020E0A0E6B0E001C01D92A336B207E1F700
       :100010001F920F920FB60F9211242F938F939F93DD
       :10002000809162008823F1F0813071F4809160004A
       :100030009091610001979093610080936000009718
       :1000400039F41092620004C08091600090916100C8
       :100050009BBD8ABD9F918F912F910F900FBE0F90E6
       :100060001F90189580916000909161000196909387
       :100070006100809360008F3F23E0920749F721E001
       :1000800020936200E5CF83E88FBD8EB581608EBD81
       :100090001BBC1ABC82E087BB84E089BF78940895BA
       :1000A00083E88FBD8EB581608EBD1BBC1ABC82E01B
       :1000B00087BB84E089BF789485B7806885BF8895C1
       :1000C00085B78F7785BFF8CFF89400C0F894FFCF3D
       :00000001FF

       The -j option indicates that we want the information from the .text and .data segment
       extracted. If we specify the EEPROM segment, we can generate a .hex file that can be used
       to program the EEPROM:

           $ avr-objcopy -j .eeprom --change-section-lma .eeprom=0 -O ihex demo.elf demo_eeprom.hex

       There is no demo_eeprom.hex file written, as that file would be empty.

       Starting with version 2.17 of the GNU binutils, the avr-objcopy command that used to
       generate the empty EEPROM files now aborts because of the empty input section .eeprom, so
       these empty files are not generated. It also signals an error to the Makefile which will
       be caught there, and makes it print a message about the empty file not being generated.

Letting Make Build the Project

       Rather than type these commands over and over, they can all be placed in a make file. To
       build the demo project using make, save the following in a file called Makefile.

       Note:
           This Makefile can only be used as input for the GNU version of make.

       PRG            = demo
       OBJ            = demo.o
       #MCU_TARGET     = at90s2313
       #MCU_TARGET     = at90s2333
       #MCU_TARGET     = at90s4414
       #MCU_TARGET     = at90s4433
       #MCU_TARGET     = at90s4434
       #MCU_TARGET     = at90s8515
       #MCU_TARGET     = at90s8535
       #MCU_TARGET     = atmega128
       #MCU_TARGET     = atmega1280
       #MCU_TARGET     = atmega1281
       #MCU_TARGET     = atmega1284p
       #MCU_TARGET     = atmega16
       #MCU_TARGET     = atmega163
       #MCU_TARGET     = atmega164p
       #MCU_TARGET     = atmega165
       #MCU_TARGET     = atmega165p
       #MCU_TARGET     = atmega168
       #MCU_TARGET     = atmega169
       #MCU_TARGET     = atmega169p
       #MCU_TARGET     = atmega2560
       #MCU_TARGET     = atmega2561
       #MCU_TARGET     = atmega32
       #MCU_TARGET     = atmega324p
       #MCU_TARGET     = atmega325
       #MCU_TARGET     = atmega3250
       #MCU_TARGET     = atmega329
       #MCU_TARGET     = atmega3290
       #MCU_TARGET     = atmega32u4
       #MCU_TARGET     = atmega48
       #MCU_TARGET     = atmega64
       #MCU_TARGET     = atmega640
       #MCU_TARGET     = atmega644
       #MCU_TARGET     = atmega644p
       #MCU_TARGET     = atmega645
       #MCU_TARGET     = atmega6450
       #MCU_TARGET     = atmega649
       #MCU_TARGET     = atmega6490
       MCU_TARGET     = atmega8
       #MCU_TARGET     = atmega8515
       #MCU_TARGET     = atmega8535
       #MCU_TARGET     = atmega88
       #MCU_TARGET     = attiny2313
       #MCU_TARGET     = attiny24
       #MCU_TARGET     = attiny25
       #MCU_TARGET     = attiny26
       #MCU_TARGET     = attiny261
       #MCU_TARGET     = attiny44
       #MCU_TARGET     = attiny45
       #MCU_TARGET     = attiny461
       #MCU_TARGET     = attiny84
       #MCU_TARGET     = attiny85
       #MCU_TARGET     = attiny861
       OPTIMIZE       = -O2

       DEFS           =
       LIBS           =

       # You should not have to change anything below here.

       CC             = avr-gcc

       # Override is only needed by avr-lib build system.

       override CFLAGS        = -g -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) $(DEFS)
       override LDFLAGS       = -Wl,-Map,$(PRG).map

       OBJCOPY        = avr-objcopy
       OBJDUMP        = avr-objdump

       all: $(PRG).elf lst text eeprom

       $(PRG).elf: $(OBJ)
           $(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)

       # dependency:
       demo.o: demo.c iocompat.h

       clean:
           rm -rf *.o $(PRG).elf *.eps *.png *.pdf *.bak
           rm -rf *.lst *.map $(EXTRA_CLEAN_FILES)

       lst:  $(PRG).lst

       %.lst: %.elf
           $(OBJDUMP) -h -S $< > $@

       # Rules for building the .text rom images

       text: hex bin srec

       hex:  $(PRG).hex
       bin:  $(PRG).bin
       srec: $(PRG).srec

       %.hex: %.elf
           $(OBJCOPY) -j .text -j .data -O ihex $< $@

       %.srec: %.elf
           $(OBJCOPY) -j .text -j .data -O srec $< $@

       %.bin: %.elf
           $(OBJCOPY) -j .text -j .data -O binary $< $@

       # Rules for building the .eeprom rom images

       eeprom: ehex ebin esrec

       ehex:  $(PRG)_eeprom.hex
       ebin:  $(PRG)_eeprom.bin
       esrec: $(PRG)_eeprom.srec

       %_eeprom.hex: %.elf
           $(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $< $@     || { echo empty $@ not generated; exit 0; }

       %_eeprom.srec: %.elf
           $(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O srec $< $@     || { echo empty $@ not generated; exit 0; }

       %_eeprom.bin: %.elf
           $(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O binary $< $@     || { echo empty $@ not generated; exit 0; }

       # Every thing below here is used by avr-libc's build system and can be ignored
       # by the casual user.

       FIG2DEV                 = fig2dev
       EXTRA_CLEAN_FILES       = *.hex *.bin *.srec

       dox: eps png pdf

       eps: $(PRG).eps
       png: $(PRG).png
       pdf: $(PRG).pdf

       %.eps: %.fig
           $(FIG2DEV) -L eps $< $@

       %.pdf: %.fig
           $(FIG2DEV) -L pdf $< $@

       %.png: %.fig
           $(FIG2DEV) -L png $< $@

Reference to the source code

Author

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