The main character in embedded programming is the microprocessor one is going to use. You should know it´s pins and how they are reserved, to be able to write your program according to their applications. If you want to deliver a package to Mr. X you should know at which room number you have to knock. I`ve used ATtiny 44 and my board design is based on the fabacadamy's 6. electronics design declarations two weeks ago. I've added a 16MHzresonator, one LED and a button to my board. Now, I have to program my board via my programmer I have produced in the 4th week.

ATtiny44 Datasheet

equipped AVR

programmable chip

milled Board

Pin configuration
Possible PWM (Pulse Width Modulation) is on PA5,PA6 and PA7 and PB2. PWM you need for Informationtransfer and often to regulate the conversion of energy into technical systems.

marked vcc

Vcc pin is marked with a ring in the corner.

equipped AVR

The Debug wiring on pin PB3.

How to Reset. equipped AVR

General informations about PortA: equipped AVR

General informations about PortB: equipped AVR

What happens to unconnected pins? equipped AVR

Some informations about internal 8MHz clock: equipped AVR

How can I use an external clock on PB0? equipped AVR

A crystal needs two capacitors.See below how they are connected and which capacitors are recommendet for frequency range (MHz). A resonators architecture is the same just build-in. Use an external Resonator or crystal between Port PB0 and PB1: equipped AVR

equipped AVR

equipped AVR

Finally, the operating modes, like temperature and voltage: equipped AVR

equipped AVR

The Architecture of a ATtiny44

The AVR architectur of ATtiny44 is based on Harvard architecture. CPU (Central Processing Unit) is the core of a processor. CPU has two duties: 1. execute instructions and 2. regulate processes within the system. We can split the CPU up into A Instruction Processor and B Data Processor. The Data Processor is responsible for calculations and data processing. Main feature of it is ALU (Arithmetic Logical Unit) for all calculations. Register is an other important feature for saving all results in a storage. It has an Akkumulator which is devided into MR (Multiplier),L (Linkregister for adding and MBR (Memory Buffer Register) serving for communication between Register and Instruction Processor.
The Instruction Processor ist devided in two sectors: 1. Instructions Decoder and Register. Register itself is split into IR (Instrucion Register) for current instructions; MAR (Memory Address Register), where to find this instruction; and PC (Program Counter) which knows the address of the upcoming instruction.

One can split the process in two stages: 1. Fetch Stage, 2.Execution Stage

CPU architecture drawing

It is characteristical that a processor is executing one instruction for one data value: (SISD- Single Instruction, Single Data). A processor is always working with data, instructions and addresses. Data and programs are stored in a storage and are accessible from outside.

In the datasheet for ATtiny you will find a drawing with thick lines called Data Bus 8-bit. It is bi-directional. A data bus consists of several parallel wires transporting different values. The thicknes of a bus is defined by the number of wires.

USB (universal serial bus) is a serial connection one line only. A processor is working with a parallel connection. By this several informations can be transported at once in both direction. The number of wires defines how many memory units can be addressed. The datasheet says 8-bit, that means 2^8 = (in total 256 Bit) memory units can be addressed at the same time. In addition 32 general purpose working registers are directly connected to ALU.

AVR architecture

Programming Attiny44

Main feature for me is, how to get out of my computer into my selfmade board. I really tried to understand it, because it was a bit like roulette: one time it worked out and next time it didn´t work out. I try to repeat what I have learned: To programm the new board first I have to make it programmable, set devices, fuses, clock and so on. I downloaded the Makefile from fabacademy's homepage, changed the name into 'Makefile' and created a new folder for Makefile and C-program. Both have to be in the same folder. I adapted the makefile fo my needs, like the clock: from 20MHz to 16 and compared the fuse addresses. For the fuse address I can look up in Internet: Engbedded is a homepage for calculating fuse address.
Then I downloaded 'hello_world_c' from fabacademy' homepage, modified it, too, and put it in the same folder. I opend Terminal, changed to my folder and run 'make' See below the report:

set fuses

This 'make'advice created o-, hex- and elf- files. See below how I connected my board and my programmer to my computer:


Problems with programming

But I got quiete some problems with programming LED and button on my hello board. Sometimes it worked out sometimes my computer couldn´t find usb device. I´ve checked all connections again and again. I did some logic analysings and found out that may be my soldered resonator is not working exactly. But Tobias our instructor said if you measure the resonator the measuring instrument can cause distractions. Later on I´ve realised together with Daniele , our Guru from Kamp-Lintfort that 1. my programmer has only one opened jumper and not two. That means my programmer gets power through my Hello_board, and 2. my TTL Kabel is a replica and my Mac has problems to find its device or get confused with the address. I odered a new one.

Blinking LED

I took the blinking LED C-programm from Marcel and made some changes: instead of writing ten times: 'LED on' and 'LED off' I programmed an if-clause with a counter. Then I created a new folder. I copied a Makefile into this folder and run 'make' on Terminal. Afterwards, I connected my boards to my computer and wrote 'make flash'. Now, the blinking programm was flashed on the hello-board. See below:


LED blinking text for downloading:


As I´ve got so much trouble with my device connections and my knowledge about programming and electronics is still small, I decided to start each project very low and easy with Arduino. I wrote a sketch with the help of examples in Arduino and testet it with an Arduino Uno and a breadboard, too, as seen below:


Then I connected my programmer to my computer, I did not connect my Hello_Board to my computer because of the above mentioned problems. See below:


The aim was to press a button on my hello_board and the led on my hello_board is blinking in pre-defined speed and amount. Arduino Program for my Hello_board:

Arduino for my Hello Led


For this I need my original FTDI cable, I´m still waiting for. In between I developed the program for the arduino board, as seen below, this worked out: Arduino for Breadboard

Then I wrote a sketch for my hello_board, included the SoftwareSerial package, see below:

Arduino for my Hello_Echo

As I still couldn´t test it on my Mac, I tested it together with Danieles Linux operation system:

Arduino for my Hello_Echo

To fill up my hello_echo feature T´ve tried the same setting, with an original ftdi cabel and adapted hello-echo-44 c program.. The cheap one I´ve bought before is not suitable for Mac as written in its Datasheets. I took the Makefile for my Atmega328p and adapted it to Attiny44. Then I took the hello_echo_file from the fabacademy's tutorial page and included stdio libary. I programmed my hello board with my programmer and then I opened Arduino´s Monitor. I copied the plain c-file in an Arduino window, after adapted all settings in Tool (Board: Attiny 44; Prozessor: Attiny44; Port device: usb-serial-ALO24B6; Programmer as usual: usbtiny. I compiled it and then uploaded the echo file. After opening Serial Monitor I printed the letters. As you can see below, there was a mismatch first with the baudrate:

plane plane

I set the monitor on 9600 Baudrate, this didn´t work out. Then I switched to 115200 baud.

plane plane

I set the lfuse as recommended on 0x5E and changed the baudrate as above and it worked out.


Enclosed are two files, a Makefile for Attiny44 and hello_ech44.c, as I mentioned before, adapted from FabAcademy's tutorials.

Makefile for Attiny44
hello_echo44.c. You can test it directly on a serial port terminal application like Coolterm for Mac or copy it to Arduino. In Arduino you have to include <stdio.h> library.