Embedded C welcomes you!

Содержание

• What do we need?
• AVR Studio 5
• Configuring AVR Studio 5
• Building your code
• Attention: AVR Studio 4 Users
• Using AVRDude with FreeISP
• Using eXtreme Burner AVR
• Video

Hello folks! Now that you are aware of the different port operations in AVR, we can move forward to actually code our way right through it! Since we will be using C (in fact Embedded C), the best software is the AVR Studio 5 by Atmel. The latest version is 5.1 which was updated in February 2012. The best part is that it is very interactive, user friendly, has awesome UI and unlike other compilers, it is totally free of cost. You can download it from here.

For those who do not want to register in order to download, I am posting the direct download links of the images here. Please report to me if the links are not proper, I will update them in that case.

(396MB) Contains AS5.1, ASF, AVR Toolchain (616MB) Also contains Visual Studio Shell .NET 4.0 (Download it if your system will not be connected to the internet during installation).

Those of you who like to learn how to use the AVR Simulator, you would prefer to skip this post and move on to the next.

You have been familiar with C (I presume). You have been working with normal data types and have been writing codes that run on a computer. But now, we will be using the same C (with some modifications) to run our microcontroller (MCU). The C used in embedded systems design is called Embedded C. Here, you will come across the same if, for, while, do while, case, switch, etc, but you will be introduced to newer data types (actually a modification of the existing ones), newer libraries, newer built-in functions and newer registers!

What do we need?

The following software will assist you in your work. You can download them from the links provided. We will discuss them one by one here.

– to write, simulate, debug and emulate your code – burns your hex code into the MCU – GUI for AVRDude for use with AVRISP or USBtinyISP programmers
• eXtreme Burner AVR – GUI for use with USBasp programmer

Installation

Installation of these software is pretty straightforward. You should not face any trouble in it. During the installation of AVR Studio 5, it might need to install some other stuffs before the actual installation begins. If you face any trouble in installation, you are free to drop a comment below.

AVR Studio 5

Let’s have a look at the features of AVR Studio before we proceed.

• It is an Integrated Development Environment (IDE) for AVR Software.
• It allows chip simulation and in-circuit emulation.
• It supports the whole AVR family of Microcontrollers (MCUs).
• It has easy to use User Interface (UI) and gives complete overview.
• It uses same UI for simulation and emulation.

Creating your first AVR Project

Here is a step-by-step guide regarding how to create your first AVR Project using AVR Studio 5.

• After installation, open AVR Studio 5 from Start → All Programs → Atmel AVR Tools → AVR Studio 5.0
• After opening, you will see a Start Page like this. Click on “New Project…“.

AVR Studio 5 Start Page

• Then, you will see the following dialog box. Choose AVR GCC from the ‘Installed Templates’ pane, and then choose Empty Executable Project. Now, you can give any name to it, say MyFirstProject and choose an appropriate location in your hard drive. Check Create directory for solution. Click on OK.

AVR Studio New Project

• Now, you will see the Device Selection dialog box. As you can see, AVR Studio supports all the AVR MCUs! The list is huge! Choose your device from this list. We choose ATmega32. Click OK.

AVR Studio Device Selection

AVR Studio New Project Start Screen

• Congratulations! You have successfully created your first AVR Project! Now to further proceed with it, we need to write a code, which is discussed in the next part.
• Have a look at the awesome AVR Studio IDE. Feel free to explore the software. We will discuss some of the required components as and when necessary.

Writing the code

LED Blinking Schematic

Now that you have successfully created your new project, we need to write a code in the AVR Studio Code Window. Let’s write the code for the problem statement discussed in this post. We will write the code for blinking an LED. The schematic for physical connection is given below. Please note that it’s just a schematic of the region of interest. For full schematic, view the circuit diagram of your development board.

Now most of you will copy and paste the code. But I suggest you to type the whole code. This will introduce you to a whole new feature! While typing any keyword or inbuilt function, AVR Studio 5 automatically displays a list of possible functions/keywords that you wish to type. You can select it and hit enter key. This increases your typing speed also (somehow!). Plus it also gives you greater confidence in writing the code.

Code Explained:

• #include avr/io.h is a header files which provides you with various i/o operations like DDRx, PINx, PORTx, etc.
• #include util/delay.h is a header file which provides you with inbuilt delay functions like _delay_loop_1(), _delay_loop_2(), _delay_ms(), _delay_us() , etc.
• Rest of the code is simple and straightforward. For details regarding how to use DDRx and PORTx, view this post.
• _delay_ms(xxx) provides a delay xxx milliseconds whereas _delay_us(xxx) provides a delay of xxx microseconds. There are two more types of delays which are used commonly, _delay_loop_1() and _delay_loop_2() , but to understand their concept, you need to be familiarized with timers, which we will discuss later.

Configuring AVR Studio 5

There are two things that you must configure in order to make your code run in your MCU in a better way.

• Setting up your clock frequency F_CPU
• Choosing Optimization Level

Setting up Clock Frequency F_CPU

This is a very essential step. This is because if you don’t set your clock frequency, the whole timing would go wrong. _delay_ms(500) will wait for 500ms, but it counts with respect to your clock frequency. If your F_CPU setting is wrong, it won’t wait for 500ms. It will either wait longer or for lesser time. By default, delay.h defines F_CPU=1000000UL (1MHz). UL stands for unsigned long. But this isn’t always the case. Check your development board if any crystal oscillator is present or not (across the XTAL pins). If it is present, note down the exact value of the frequency. If no, then choose either 1MHz, 2MHz, 4MHz or 8MHz depending upon the fuses set in your MCU (I expect that correct fuses must have been written. We will discuss about fuses later).

Note: You must set fuse bits for a new AVR microcontroller. These fuse bits will specify the correct clock frequency (whether to follow internal clock or external clock) and many other settings. They are set only once, and hence MUST be set correctly, or else you will render your MCU useless. To learn about fuses, view this.

Now, how to put? Well, the simplest way is to add the following code before including the header files.

You need to add it before every code you write. Or else, you can go to Project menu → MyFirstProject Properties (Alt+F7) → Toolchain → AVR/GNU C Compiler → Symbols → Add F_CPU=16000000UL to Defined Symbols.

Always check this out before compiling your code.

Optimizing your Code

You need to choose an appropriate optimization level for your code. Choosing the right optimization level will result in smaller hex file and faster compilation time. You can do it so by going to Project menu → MyFirstProject Properties (Alt+F7) → Toolchain → AVR/GNU C Compiler → Optimization → Choose -O2 as Optimization Level.

To know what optimization is, view this. For more details regarding optimization of code in AVR, visit this page. For details regarding the meanings of different optimization levels, view the GCC-GNU User Manual.

Building your code

After writing the code and configuring it, we proceed to build it. To do so, go to Build menu → Build Solution (F7). Now, it builds your AVR-GCC project. After the build process has finished, you will see the details in the Output window (below the source code window). There, you can check your memory usage and the build log. In the end, it shows Build Succeeded. If it doesn’t show, check you code once again and check whether you have configured your project properly. If still it shows Build Unsuccessful, then post your queries here, I will look into the matter.

Now, once you have built your code, a .hex file has been generated for your .c file. You can find it in the following directory

The next step is to burn this hex file into your MCU. For this, we will use avrdude. AVR Programming can also take place from within AVR Studio 5, but at present, AVR Studio 5 has support only for the current Atmel Programmers. But most of the programmers available are AVRISP, AVRISP mkII, USBtinyISP, USBasp, etc. So, we will be using avrdude.

If you use AVRISP and USBtinyISP, or want to learn how to use avrdude GUI, proceed to the next section. If you use USBasp, then skip the next section and jump over to the topic eXtreme Burner AVR.

Attention: AVR Studio 4 Users

There will be many who have previously worked with AVR Studio 4. The interface of AVR Studio 5 is a lot different than its earlier editions. Also, the AS4 project is not supported by AS5. For that, you can open AS5, go to File menu → Import → Import AVR Studio 4 Project. This converts AS4 project into AS5 solution and then opens in AS5.

Using AVRDude with FreeISP

AVRDude stands for AVR Downloader Uploader. It is a free software that comes with WinAVR package. It’s an executable program which can be run using the command prompt. To have a detailed idea of how avrdude works and how to run it using command prompt, view this page. But if you have an AVRISP programmer, we have a GUI for you! Its called FreeISP. The download link is provided at the top.

Please Note: Apart from FreeISP, there are many more GUI for avrdude, like the AVRDude-GUI, AVR8 Burn-O-Mat, etc. They all are simple to use, but I have discussed only FreeISP and eXtreme Burner here. But unlike FreeISP or eXtreme Burner, AVRDude-GUI supports all kinds of programmers supported by avrdude.

• Open FreeISP by clicking it’s icon. If an error like Error reading application settings pops up, simply click OK.

• In the window that opens, choose the paths of your avrdude.exe file and MyFirstProject.hex file. If you have an EEPROM file, choose the path, or else leave it blank. (For the above code, leave it blank).
• Choose you device and the COM port.
• Choose AVRISP as the programming hardware.
• Make sure that only ‘Program Flash’ is checked.
• IMPORTANT : Make sure that you program only flash (and EEPROM wherever necessary). DO NOT PROGRAM FUSE BITS AND LOCK BITS without any prior knowledge, or else you might end up damaging your AVR permanently.
• Click Program.

After you click program, FreeISP invokes avrdude and passes the required comments to it as per your inputs. Then avrdude reads your device and verifies your device ID and your chip signature. After that, it erases the flash and then writes the new hex file specified by you into the flash. Then it once again reads the flash in order to verify the data. And thus after all this, your code is burnt into the MCU and your MCU is ready to use! It might have already started to respond to your code… check that the LEDs must be blinking!

If programmed correctly, you should see something like this.

Now, if you use USBasp programmer, we have another awesome GUI for you, eXtreme Burner AVR !

Using eXtreme Burner AVR

Now for those who use USBasp programmer, the best GUI that I could find is the eXtreme Burner AVR. This GUI has been developed by Avinash Gupta of eXtreme Electronics, India. You can find his tutorial here. It is available for Windows XP, Windows Vista/7 (32/64 bit), Linux (Fedora 10, Ubuntu 10.10). A few screen shots (Windows) are shown below.

GUI Software for USBasp

GUI Software for USBasp Burn Progress

GUI Software for USBasp Task Complete!

So, I guess we are done regarding how to use AVR Studio 5. In the next post, we will learn to use the AVR Simulator and Debugger. Till then, you can try out various stuffs. You can connect more than one LED and create different blinking patterns! You can do whatever you want! And you can also post comments down here to let me know! 😉

Video

This is a simple demonstration of the traditional Hello World of microcontrollers LED Blinking. The video is made by Lavin Khandelwal for maxEmbedded. He has used the low cost 28 pin AVR Development Board and the USBasp AVR Programmer by eXtreme Electronics. He used the eXtreme Burner for burning the code.

If you have any kind of suggestions, clarifications, constructive criticism etc, you can post your comments below! 🙂 I will be glad to see them! Also you can grab the RSS Feeds or subscribe to my website to stay updated!

Источник: maxembedded.com