// main.c in led project // #define F_CPU 16000000UL #include <avr/io.h> #include <util/delay.h>  #define BLINK_DELAY_MS 1000 #define ON_DELAY_MS 100 #define OFF_DELAY_MS BLINK_DELAY_MS - ON_DELAY_MS  int main (void) {  /* set pin 5 of PORTB for output*/  DDRB |= _BV(DDB5);   while(1) {   /* set pin 5 high to turn led on */   PORTB |= _BV(PORTB5);   _delay_ms(ON_DELAY_MS);    /* set pin 5 low to turn led off */   PORTB &= ~_BV(PORTB5);   _delay_ms(OFF_DELAY_MS);  } } 

(tlxde)danp@localhost:~/project/led/bin/Release$ /home/danp/Downloads/arduino-1.8.1/hardware/tools/avr/bin/avrdude -C/home/danp/Downloads/arduino-1.8.1/hardware/tools/avr/etc/avrdude.conf -v -patmega328p -carduino -P/dev/ttyUSB0 -b57600 -D -Uflash:w:led.elf.hex:i   avrdude: Version 6.3, compiled on Dec 16 2016 at 12:32:01          Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/          Copyright (c) 2007-2014 Joerg Wunsch           System wide configuration file is "/home/danp/Downloads/arduino-1.8.1/hardware/tools/avr/etc/avrdude.conf"          User configuration file is "/home/danp/.avrduderc"          User configuration file does not exist or is not a regular file, skipping           Using Port                    : /dev/ttyUSB0          Using Programmer              : arduino          Overriding Baud Rate          : 57600          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: 2          Firmware Version: 1.16          Vtarget         : 0.0 V          Varef           : 0.0 V          Oscillator      : Off          SCK period      : 0.1 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 "led.elf.hex" avrdude: writing flash (176 bytes):  Writing | ################################################## | 100% 0.07s  avrdude: 176 bytes of flash written avrdude: verifying flash memory against led.elf.hex: avrdude: load data flash data from input file led.elf.hex: avrdude: input file led.elf.hex contains 176 bytes avrdude: reading on-chip flash data:  Reading | ################################################## | 100% 0.05s  avrdude: verifying ... avrdude: 176 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.  (tlxde)danp@localhost:~/project/led/bin/Release$ 

// main.c #include <stdio.h> #include "uart.h"  int main(void) {   init_uart();   stdout = &uart_output;   printf("Hello, world!\n");    while(1);    return 0; } 

// uart.c #include <avr/io.h> #include <stdio.h> #include "uart.h"  #ifndef BAUD #define BAUD 9600 #endif #include <util/setbaud.h>  /* http://www.cs.mun.ca/~rod/Winter2007/4723/notes/serial/serial.html */  FILE uart_output = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE); FILE uart_input = FDEV_SETUP_STREAM(NULL, uart_getchar, _FDEV_SETUP_READ);  void init_uart(void) {     UBRR0H = UBRRH_VALUE;     UBRR0L = UBRRL_VALUE;      UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */     UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */ }  int uart_putchar(char c, FILE *stream) {     if (c == '\n') {         uart_putchar('\r', stream);     }     loop_until_bit_is_set(UCSR0A, UDRE0);     UDR0 = c;     return 0; }  int uart_getchar(FILE *stream) {     loop_until_bit_is_set(UCSR0A, RXC0);     return UDR0; } 

// uart.h int uart_putchar(char c, FILE *stream); int uart_getchar(FILE *stream);  void init_uart(void);  /* http://www.ermicro.com/blog/?p=325 */  extern FILE uart_output; extern FILE uart_input;