AVR Serial Programmer

First I think, how to build a USBasp programmer.But I have n't a usb programmer to flash the firmware to it. Then decided to create a serial programmer and flash the firmware through this programmer to  atmega8. My  AVR serial programmer will transform hex file to most AVR microcontroller. It can build using few readily  available components. This programmer is compatible with popular avrdude software or PonyProg software.

We will be using the serial port for burning. First, we have to develop a burning circuit for it.

REQUIRED COMPONENTS 

Resistors :             10k     - 2
                           4.7k    - 2
                           15k     - 1

Zener diode :         5.1v   - 2

Diode :               1N4148 - 1

Transistor :      BC549/48 -  1

9-PIN RS232 female connector

serial programmer

Connect the serial programmer with your target micro-controller. Supply external +5V to target microcontroller from  your PC's usb port(pin1 is +5V and pin4 is Ground) or from +5V DC power supply.

atmega8 target microcontroller

    For burning hex files, connect the DB9-female connector to your serial port of PC. Pin 9 & pin 10 are connected by a 12 MHz crystal oscillator, which is the external clock.You should watch for RESET,XTAL1,XTAL2,SCK,MISO,MOSI, GND, +5 pins, and connect. If you are using any other microcontroller, as mentioned above, you should change accordingly

   On Linux we install required packages for avr programming:
binutils: Tools like the assembler, linker, etc.
gcc-avr: The GNU C compiler (cross-compiler for avr).
avr-libc: Package for the AVR C library, containing many utility functions.
avrdude: AVRDUDE is a very popular command-line program for programming AVR chips.

LED BLINKING PROGRAM

We are writing first program  for the atmega8 microcontroller, which has a 28-pin, 8-bit, RISC architecture.Refer to the datasheet for the various pins of atmega8 AVR microcontrollers.

Here is our first porgram ledblink.c :

/* An LED blinking program */
#define F_CPU 12000000UL
#include<avr/io.h>
#include<util/delay.h>

void sleep(uint8_t msec)
{  while(msec)
  {
    _delay_ms(1); /* ms delay */
    msec--;
  } 
}

main()
{
   DDRD |= (1<<PD7);
   while(1)/*50 ms delay*/
   {
    PORTD &= ~(1<<PD7); /* PD7 LOW */
    sleep(50);
    
    PORTD |=(1<<PD7); /* PD7 HIGH */
    sleep(50); /*50 ms delay */
   }

}

Here we use 13nth(PD7) pin of microcontroller as out put pin for led blinking

COMPILATION

Compile the C code using the command below:

avr-gcc -mmcu=atmega8 -Os ledblink.c 

which will result in object file a.out Now, we will covert it to hex file, suitable for burning to the microcontroller's memory.

avr-objcopy -j .text -j .data -Oihex  a.out  ledblink.hex

We are converting it to a hex file because, for burning the code to atmega8, we will use avrdude, whose input file must be a .hex file.

Notice that you can cat the ledblink.hex file.

:1000000012C019C018C017C016C015C014C013C044
:1000100012C011C010C00FC00EC00DC00CC00BC06C
:100020000AC009C008C011241FBECFE5D4E0DEBF5E
:10003000CDBF0DD01AC0E4CF07C0E7EBFBE031978E
:10004000F1F700C0000081508823B9F7089581B30B
:10005000806C81BB82B38F7382BB82E3EDDF82B39E
:0E006000806C82BB82E3E8DFF5CFF894FFCF1F
:00000001FF

BURNING THE CODE

Now, we will burn ledblink.hex to the  target atmega8 microcontroller

avrdude -p m8 -c ponyser -P /dev/ttyS0 -U flash:w:ledblink.hex

Connect an LED with 1k resistor to pin 13 and grounded it. 

Notice that you can see the LED at pin 13 blinking.

*****Happy Coding*****