Install CrossPack Development Environment

First, install CrossPack, which provides “the GNU compiler suite, a C library for the AVR, the AVRDUDE uploader and several other useful tools.” Make sure you completely close your Terminal program (if you had it running) and restart it after the installation, to pick up the location it adds to your command search path.

Test the Programmer and Connectivity

Once installed, connect your programmer (I have a couple of USBtinyISPs, so that’s what I used) to your computer and target board and test that the programmer is working and sees your ATtiny:

$ avrdude -c usbtiny -p attiny25
avrdude: AVR device initialized and ready to accept instructions

avrdude done. Thank you.


If you get any other response, check the troubleshooting notes at the bottom of Jeff Keyzer’s AVR toolchain installation page.

Create Blink Code

The CrossPack web page includes a blinky demo project, but it’s written for a different microcontroller and requires minor adaptation to work on the ATtiny25. Follow along both here and there for greatest insight.

In your Terminal window,

$ avr-project blink
Using template: /usr/local/CrossPack-AVR-20120217/etc/templates/TemplateProject
$ cd blink/firmware
$ ls
Makefile main.c


The Crosspack example is written for an ATmega8, which has more I/O ports than the ATtiny. The ATtiny has a single I/O port, and it’s port B (mystery of the universe why not A). So adapting the example code, use your favorite text editor to insert into main.c to create the following (picking whichever pin you’d like to use for your LED):

#include <avr/io.h>
#include <util/delay.h>

#define LEDPIN (3)

int main(void) {
    DDRB = 1 << LEDPIN;  //  make only the LED pin an output
    while (1) {
        char i;
        for (i = 0; i < 10; ++i) {
            _delay_ms(50);
        }
        PORTB ^= 1 << LEDPIN;
    }
    return 0;   /* never reached */
}

Calculate Fuse Values and Edit the Makefile

Use the Engbedded AVR fuse calculator to calculate the command-line values to set all the ATtiny behavior flags. Use AVR part name: ATtiny25, uncheck (for this example) Divide clock by 8 internally, and scroll down to Current settings. You should see something like

-U lfuse:w:0xe2:m -U hfuse:w:0xdf:m
-U efuse:w:0xff:m


Back in Terminal, edit Makefile . Update the following lines:

DEVICE = attiny25
PROGRAMMER = -c usbtiny
FUSES = -U lfuse:w:0xe2:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m


(using whatever programmer you have and any additional flags it needs) and save and exit the Makefile .

Compile and Load the Program

Run

$ make
avr-gcc -Wall -Os -DF_CPU=8000000 -mmcu=attiny25 -c main.c -o main.o
avr-gcc -Wall -Os -DF_CPU=8000000 -mmcu=attiny25 -o main.elf main.o
rm -f main.hex
avr-objcopy -j .text -j .data -O ihex main.elf main.hex
avr-size --format=avr --mcu=attiny25 main.elf
AVR Memory Usage
----------------
Device: attiny25

Data: 0 bytes (0.0% Full)
(.data + .bss + .noinit)


to build the program. If you get errors instead, double-check main.c around the line the compiler indicates.

Run

$ make flash
avrdude -c usbtiny -p attiny25 -U flash:w:main.hex:i

avrdude done. Thank you.


to program the IC. Run

$ make fuse
avrdude -c usbtiny -p attiny25 -U lfuse:w:0xe2:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

avrdude done. Thank you.


to burn the fuse bits.

Behold Blinky Goodness

The board I’m developing doesn’t have an LED on it, so I clipped my logic analyzer to ground and I/O pin B3 (IC pin 2) to test for blinking.

1 Hz blinking on my I/O pin. Fundamental programming accomplished.