Introduction

If a hardware is the body of a person then the program running on it is his soul. So it is so much important that to program someone's soul with so much patience so that it won't destroy his physical existence.Hardware programing is an art of integrating life into inorganic materials . I have been so much facinated about computer science since my early ages.So I consider this as interesting oppurtunity to understand the inner workings of a microcontroller . I have previous experience in arduino programing and a little experience in avr c .We learned basic structure of assembly programming in college so I also wanted to test some assembly coding in attiny 44

A microcontroller (or MCU for microcontroller unit) is a small computer on a single integrated circuit. In modern terminology, it is similar to, but less sophisticated than, a system on a chip or SoC; an SoC may include a microcontroller as one of its components. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Program memory in the form of ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips like ADC(analog to digital converter),DAC [Digital-to-Analog Converter] etc.[wiki].

These devices are in every were. We can see embedded systems in your car ,TV, Refrigerator,Phone etc

AVR is a family of microcontrollers developed by Atmel beginning in 1996. These are modified Harvard architecture 8-bit RISC single-chip microcontrollers. AVR was one of the first microcontroller families to use on-chip flash memory for program storage, as opposed to one-time programmable ROM, EPROM, or EEPROM used by other microcontrollers at the time. AVR microcontrollers find many applications as embedded systems; they are also used in the Arduino line of open source board designs.

The ATtiny44 is a high-performance, low-power Microchip AVR RISC-based CMOS 8-bit microcontroller.It combines 4KB ISP flash memory, 256-Byte EEPROM, 256B SRAM, 12 general purpose I/O lines .The ATtiny44 consistof 32 general purpose working registers, an 8-bit timer/counter with two PWM channels, a 16-bit timer/counter with two PWM channels, internal and external interrupts, an 8-channel 10-bit A/D converter and a programmable gain stage (1x, 20x) for 12 differential ADC channel pairs. It has a programmable watchdog timer with internal oscillator.The a internal calibrated oscillator and three software selectable power saving modes makes it suitable for small embedded products . By executing powerful instructions in a single clock cycle the device achieves throughputs approaching 1 MIPS per MHz .It also balance power consumption and improve processing speed.

If you want to know more about ATtiny44 just go through the datasheet

These are some basic details about the chip.

• VCC Supply voltage
• GNDGround
• Port B (PB3...PB0)Port B is a 4-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated.so we don't need to add a pull-up resistor externaly for button's and other purpose.
• RESETReset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running.a reset will just reset the programm that currently runnig .
• Port A (PA7...PA0)Port A is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). As inputs, Port A pins that are externally pulled low will source current if the pull-up resistors are activated

Arduino is an open source computer hardware and software company, project, and user community that designs and manufactures single-board microcontrollers and microcontroller kits for building digital devices and interactive objects that can sense and control objects in the physical and digital world.[wiki]

Since i have some basics in arduino i decided to try arduino first .

Since the original Arduino software doesnot support the ATtiny44. I have to add some Board directorys for adding my ATtiny44 board to my arduino enviournment

open File -> Preferences

Copy and paste the below URL in the Additional Boards Manager URLs field.

Open Tools -> Board -> Board Manager
Search for attiny and click to install the board file.

further, We need to install the operating system driver for our USBTinyISP.I usde a driver developed by Adafruit you can download that Here

So next we have to code our board in arduino .

Here is the ATTiny44 to Arduino PIN map

ATTiny44 PINs

This is the schmatic of my PCB. we have to refer our schmatic befor coding our board.

We are using the USBtiny programmer we made during the Week 5 assignment for programming our board. The ISP Programming of ATtiny 44 using six pins .These are the 6 pins.

• SCK(Serial Clock): Programming clock, generated by the In-System Programmer (Master)
• MOSI(Master Out - Slave In )Communication line from In-System Programmer (Master) to target AVR being programmed (Slave )
• MISO( Master In - Slave Out ): Communication line from target AVR (Slave) to In- System Programmer (Master)
• RST(Reset):To enable In-System Programming, the target AVR Reset must be kept active. To simplify this, the In-System Programmer should control the target AVR Reset
• GND(Ground):Common Ground

Befor uploading the program to our board.We have to tell our IDE some more things.

• From the Tools -> board -> choose ATtiny44
• From Tools -> Processor -> choose ATtiny44
• Select Tools -> clock -> External 20 MHz
• Choose Tools -> Programmer -> USBTinyISP

Remark! ATTiny44 is defaultly set to use the Internal clock .So if you are using Arduino to program it. It will not get program initially . We have to upload the Bootloader first.

Studio 7 is the integrated development platform (IDP) for developing and debugging all AVR® and SAM microcontroller applications. The Atmel Studio 7 IDP gives you a seamless and easy-to-use environment to write, build and debug your applications written in C/C++ or assembly code. It also connects seamlessly to the debuggers, programmers and development kits that support AVR® and SAM devices.

Additionally, Studio includes Atmel Gallery, an online app store that allows you to extend your development environment with plug-ins developed by Microchip as well as third-party tool and embedded software vendors. Studio 7 can also seamlessly import your Arduino sketches as C++ projects, providing a simple transition path from Makerspace to Marketplace.

To start a new project .Just open the software and choose new project .Select Gcc C Executable Project .Then select a name and click Ok .Select Our Chicp from the next window and click on the okey button.Now the enviournment is created

Next we have to add our programmer to our enviournment. Choose Tools -> External Tools -> Fill the spaces as shown below. Put this
-c usbtiny sp -p t44 -F -v -U flash:w:$(TargetDir)$(TargetName).hex:i in the argument space

Check wether the programmer is properly configured.Open tools and check wether our programmer is added.Just test it by uploading a simple code.

I tried a simple code to blink the LEDs in my board

Before starting the programming a little bit about the programming.

DDRx DDR stands for Data direction Register, basically it is an 8-bit register which determines whether one pin will be an input or output pin. If you want the pin you connected the LED to be set as output then you should give that value of that as 1 on DDRx. Example I connected my LED to PA7, hence I have to make it as out put in DDRA.Hence I give the code to set the pin PA7 as out put by writing. DDRA=0xff; This is HEX equivalent for DDRA=ob11111111 What this does is that it will set all the pins on the PA7 as output pins.

PORTx while DDRx denotes the direction of the Pin, PORT denotes the state of it. That means if I give a value 1 in the PORT register of that pin It would be set to HIGH, or 5V in case of the micro controller.

PINx register is a dynamic register whose value will be automatically updated based on the received values of the sate of all pins, so 5V to that pin will write 1 to that register.

Now lets start programming .To build the code just click build -> Build Solution or press "F7"

This is the console result.If something wrong will happen It will be displayed here.

Upload to the Chip using the programmer .Choose Tools -> USBTiny -> OK

This is the Console output.Fortunately everything happend perfectly.

This video shows the result.

Next I decided to add alittle bit of physical intraction to my board .I programmed to turn on and off the LED with respect to the status of the switch.

This is the result video.

This week we had to compare the performance and development workflow of different architecture . As part of our asignmet we tried STM32 and ARM Architecture .You can access the details in Salman's documentation.