'Hello world' with an AVR

“Hello World” with an AVR by Vijay Raju ([email protected]) Universal Embedded Solutions Introduction: A simple program which puts the words “Hello World” on the screen is almost always the starting point for programmers learning a new language. For an embedded systems designer the equivalent to “Hello World” is a simple program to blink a set of LEDs connected to a port of microcontroller. This simple program not only allows a designer to get started with preprogramming a new controller but it also behaves as a simple check to test if all the hardware is operational. This document describes how to control a set of LEDs connected to a port of an AVR microcontroller using an EVK01 microcontroller kit with code written in assembly and in C. A section on how to achieve the same task with a bread board will be added later. The EVK01: The EVK01 is a complete microcontroller evaluation kit with all the hardware and software necessary to try our “Hello Word” program. The following are the required tools that the EVK01 provides: Basic hardware with a microcontroller, power supply, crystal and LEDs. A In-System Programmer An assembler, a compiler and in-system programming software.

Assembling Assembly: Atmel provides a free assembler and IDE for the AVR series called AVR Studio. AVR Studio is can be found on the EVK01 CD under the “Software” tab or can be downloaded from the Atmel website. Simply launch the installer and follow the simple on-screen instructions to install AVR Studio on your PC. Once the installation process has completed successfully, launch AVR Studio from the “Start” menu. Create a new project by choosing “Project->New Project” if the new project window is not already open.

Choose AVR Assembler in the project type and type in “Hello world” as your project name and initial file name. Make sure the “Create Initial File” and “Create Folder” check boxes are ticked. Choose a convenient location for you project and then click “Next”. In the “Choose Debug Platform and Device” dialog box that appears next choose the debug platform as AVR Simulator and the device as AT90S8515. Click the “Finish” button to dismiss the dialog box and open the “Hello World” project with the “Hello World.asm” file.

Now its time to fill in some code into “Hello World.asm”. Consider the following piece of code: ;********************************************************************** ;* ;* Title : AVR LEDs Upcount Sample Code ;* Version : 1.0 ;* Last updated : May 01 2003 ;* Target : AT90S8515 ;* File : LEDs Upcount.asm ;* Author(s) : Vijay Raju ;* Universal Embedded Solutions ;* ;* ;* DESCRIPTION ;* Does an Upcount on the LEDs connected to PORTA ;********************************************************************** ;**** includes **** .include "8515def.inc" ; This file provides definitions for the 8515 registers

;******************************* ;* Global Register Definitions * ;******************************* .def .def .def .def

temp Delay Delay2 Delay3

= = = =

r16 r17 r18 r19

;********************************************************************** ;* ;* RESET routine. ;* ;********************************************************************** RESET: ser temp out DDRA, temp

;Set a register ;Set Data Direction of PORTA to output

dec temp out PORTA, temp

;Upcount register ;Send register to Port

loop:

;********************************************************************** ;* ;* Provide a delay. ;* ;********************************************************************** ldi Delay3, 0x05

DLY: dec Delay brne DLY dec Delay2 brne DLY dec Delay3 brne DLY ;********************************************************************** ;* ;* Infinite Loop ;* ;********************************************************************** rjmp loop ;**********************************************************************

Type out or copy this code into “Hello World.asm” and save it using “File->Save”. Assemble (Build) this code by selecting “Project -> Build”. Once the build is complete check the Output window for the build results. The output window will read as shown below if the build was successful and “Hello World.hex” was created

The code can now be simulated by choosing “Project -> Build and Run”. Use the “Debug” menu to control program execution and the I/O view to visualize the ports, registers and other parameters.

Compiling C Code: WINAVR is an open source installer which provides a variety of open source tools including a C cross-compiler for the AVR. The WINAVR installer is available in the software section of the EVK01 CD or can be downloaded from the WINAVR project page. WINAVR makes setting up the AVR cross-compiler tool chain a breeze. Simply launch the installer and answer a few simple questions and the installer will do the rest and set up all the tools including the compiler, assemble linker, an IDE and much more. Launch Programmer’s Notepad, the IDE provided by WINAVR from the start menu when the installation is complete. Create a new project by choosing “File->New>Project” and specifying a project name in the “Project Location” dialog box. Let’s call the project “HelloWorld” in the folder “Hello World in C”. Next create a new file using “File->New->C/C++ file”. Copy or rewrite the following code into the new file you just created.

//********************************************************************* // // File Name : 'HelloWorld.C' // Title : LED Upcount // Author : Vijay Raju // Created : 22/3/2004 // Revised : // Version : 1.0 // Target MCU : Atmel AVR series // Editor Tabs : 4 // // Description : Code to do an Upcount on LEDs connected to PORTA // // This code is distributed under the GNU Public License // which can be found at http://www.gnu.org/licenses/gpl.txt // //********************************************************************* #include int main(void) { unsigned char x = 0; unsigned char a,b,c,d; //Set PortA to output DDRA = 0xFF; //infinite loop for(;;) { //Send x to PORTA PORTA = x; //Increment x x++; //Provide a delay //The optimizer may decide that this loop is useless //because it seems to do nothing. Disable the optimizer in //the makefile. i.e. dont have -O flag. for(a=0;aSave”. Now the code is all set to be compiled. Choose the “[WINAVR] Make All” option from the tools menu to compile the code.

The output window will show the following when the code compiles successfully and a “HelloWorld.hex” will be created. -------- begin -------avr-gcc (GCC) 3.3.2 Copyright (C) 2003 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiling: HelloWorld.c avr-gcc -c -mmcu=at90s8515 -I. -g -O0 -funsigned-char -funsignedbitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,adhlns=HelloWorld.lst -std=gnu99 -Wp,-M,-MP,-MT,HelloWorld.o,MF,.dep/HelloWorld.o.d HelloWorld.c -o HelloWorld.o HelloWorld.c: In function `main': HelloWorld.c:25: warning: unused variable `a' Linking: HelloWorld.elf avr-gcc -mmcu=at90s8515 -I. -g -O0 -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,adhlns=HelloWorld.o -std=gnu99 -Wp,-M,-MP,-MT,HelloWorld.o,MF,.dep/HelloWorld.elf.d HelloWorld.o --output HelloWorld.elf -Wl,Map=HelloWorld.map,--cref -lm Creating load file for Flash: HelloWorld.hex avr-objcopy -O ihex -R .eeprom HelloWorld.elf HelloWorld.hex Creating load file for EEPROM: HelloWorld.eep avr-objcopy -j .eeprom --set-section-flags=.eeprom="alloc,load" \ --change-section-lma .eeprom=0 -O ihex HelloWorld.elf HelloWorld.eep Creating Extended Listing: HelloWorld.lss avr-objdump -h -S HelloWorld.elf > HelloWorld.lss Creating Symbol Table: HelloWorld.sym avr-nm -n HelloWorld.elf > HelloWorld.sym Size after: HelloWorld.elf : section size addr .text 152 0 .data 0 8388704 .bss 0 8388704 .noinit 0 8388704 .eeprom 0 8454144 .stab 804 0 .stabstr 1400 0 Total 2356 Errors: none -------- end -------> Process Exit Code: 0

AVR Studio 4.08 can be used to simulate the compiled code. To do this an Extended COFF (Common Object File Format) file has to be created. WINAVR provides a utility produce an ExtCoff file and this utility can be called on from Programmer’s Notepad using the makefile. To do this, open the options window using “Tools->Options”. Move to the “Tools” section using the navigation pane of the window. In the “Scheme” dropdown box choose “(None – Global Tools)”. Click the “Add” button to bring up the “New Tool” dialog box. Fill in the following parameters to create a new “[WINAVR] Make ExtCoff” tool:

Click the “OK” button to create the new tool and dismiss the “New Tool” dialog box and then click “OK” again to dismiss the “Options” window. To run the ExtCoff utility choose the “[WINAVR] Make ExtCoff” from the “Tools” menu. The following output will appear in the output window and a “HelloWorld.cof” file will be created: > "make.exe" extcoff Converting to AVR Extended COFF: HelloWorld.cof avr-objcopy --debugging --change-section-address .data-0x800000 -change-section-address .bss-0x800000 --change-section-address .noinit0x800000 --change-section-address .eeprom-0x810000 -O coff-ext-avr HelloWorld.elf HelloWorld.cof Discarding local symbol outside any compilation unit: .do_copy_data_start

Discarding local symbol outside any compilation unit: .do_copy_data_loop Discarding local symbol outside any compilation unit: .do_clear_bss_start Discarding local symbol outside any compilation unit: .do_clear_bss_loop > Process Exit Code: 0

Now that the Extended COFF file is created, launch AVR Studio using the windows “Start” Menu. Choose “File->Open File…” to bring up the “Open’ Dialog box. Navigate to the “Hello World in C” directory and open the “HelloWorld.cof” file that you just created. AVR Studio will automatically create a new project with the object files and the sources and open an I/O view. Use the “Debug” menu to control the program execution and simulate the code.

Programming the chip Once you have verified that the code is running correctly with the simulator, it is now ready to be burnt into the FLASH memory of the chip. Connect the dongle provided with the kit to the parallel port and connect the programming cable (long 10-core ribbon cable) between the dongle and the connector

marked ISP on the EVK01 board. Next connect the adapter provided with the kit to the socket marked POWER and plug it into a normal wall socket. Power on the EVK01 by pressing the switch marked POWER. The red POWER LED should now glow. Begin by installing PonyProg, the programming software on the CD. You can find the PonyProg installer in the software section of the EVK01 CD or on the PonyProg Website. To install PonyProg simply launch the installer and follow the simple on screen instructions. When the installation is complete, launch PonyProg from the windows “Start” menu. When you run PonyProg for the first time you will be prompted to run the “Interface setup” and “Calibration”. To calibrate PonyProg© choose “Setup->Calibration” and follow the on-screen instructions. To setup PonyProg© for programming, choose “Setup>Interface Setup” and select the following options in the dialog box that appears: Select “Parallel”, “Avr ISP I/O” and “LPT1”

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Make sure that all the check boxes in the “Polarity of Control lines” section are not ticked, so that none of the control lines are inverted.

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Press the “Probe” button at the bottom of the dialog box. PonyProg© will check for the dongle and should display a “Test Ok” message.

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Select Ok to close the “Interface Setup” dialog box.

On the toolbar in the main window choose “AVR Micro” and “AT90S8515” in the device selection drop boxes.

Use “File->Open Device File” to load your assembled Intel Hex file “Hello World.hex” into the PonyProg buffer. Use the “Command->Erase” first to erase any existing program on the chip. Now program the FLASH on the chip with “Command -> Write Program (FLASH)”. An automatic verification of the data is performed by PonyProg.

Executing the code: The code begins executing immediately after the programming is done and PonyProg releases the RESET pin of the processor. To see the LEDs blink simply connect one of the I/O cables (shorter 10-core ribbon cable) between connectors marked PORTA and LEDS on the EVK. EEKS! I don’t own an EVK01: Coming Soon…