So I Got a Butterfly
Contents
1. AVRs are RISC machines reduced instruction set computers They are optimized to run fast by keeping the instruction set simple and efficient Most instructions execute in one clock cycle The clock itself can come from a variety of sources an internal R C oscillator which requires no external components crystal ceramic resonator or external clock signal The Butterfly is configured to run off the internal oscillator at a maximum speed of 8 MHz AVRs use a Harvard architecture which means the instructions being executed exist in a separate address space which usually means a different memory than the data those instructions manipulate It is actually a modified Harvard architecture because there is a specialized instruction which allows the processor to read the instruction memory flash as data And as the presence of the bootloader indicates it is possible for a running program to write data into the instruction memory The place to learn about a particular AVR model is its datasheet available free from the Atmel website as a pdf file Most datasheets will have a short summary 20 or so pages and a full datasheet possibly in excess of 400 pages and you may wish to download both for any MCU you are working with The datasheet is the mother load of information about the core and peripherals for a given AVR and is a necessary reference to keep handy while writing programs Assembly and C and other languages Oh My A mac2. The program was converted ported to WinAVR C Butterfly Tutorial C Baird Page 3 of 14 more on that later and that version is also available on the internet Reading through the code if you are interested in such things will teach you a lot about how to program the Butterfly and AVRs in general Atmel has also made the Intel hex file of the demo program available on its website You may reload it into your Butterfly to restore it to its pristine state Getting your Butterfly to do something When you apply power to your Butterfly it resets the MCU This is a design feature of the AVR line and most other embedded processors It is also possible to reset an AVR without removing and restoring power and later we will see how to add a reset button to your Butterfly Thus pulling the battery out and reinserting it causes a reset as does that initial removing of the cardboard spacer isolating the battery on a new Butterfly On a reset the ATMegal169 starts executing code in one of two places at the start of the application section of memory or at the start of the bootloader section of memory The application section of memory starts at a fixed address Ox0000 and the bootloader section can start at one of four different addresses depending on how we have set things up How do we tell it which we want There are some indicators fuses in nonvolatile memory which hold our choices If a certain fuse called BOOTRST is program
3. communications line on the Butterfly This is a standard method of computer communications initially used by almost all personal computers although USB has pretty much replaced it in recent years If your PC does not have a serial port a place to plug in an RS 232 connection you will need to buy a USB to serial converter to use the Butterfly s serial bootloader Or find a PC that does have a serial port There are other ways to program a Butterfly and we will briefly mention them later For now we will just concentrate on the preloaded serial bootloader The demo application program On the Butterfly s box is a flowchart of the demo program It is also reproduced in the Butterfly document see Resources Each white rectangle represents an activity or choice presented as a menu item on the LCD Until you get used to poking the joystick correctly you may find yourself jumping around to places in the flowchart other than where you expect As you see from the diagram you can set or read the time of day clock play some music enter text via the joystick or the serial line for display on the LCD read the temperature light sensor if present or an external voltage 0 5v and set various options When the joystick is inactive for a certain length of time the demo program puts the MCU to sleep to conserve the battery The demo program is a large and sophisticated piece of software and its C source code has been published by Atmel
4. be connected to the board for it to function right out of the box AVR Butterfly 4 4 ANR 0o FOE aoo Photo 1 The mighty Butterfly early model with LDR The Butterfly s 6 character 100 segment LCD is driven directly by the microcontroller there is no separate LCD controller on the board Other features of the Butterfly include a 5 position joystick shown on the right hand side of Photo 1 a piezo element for making noise or music depending on your tastes a 4 megabit nonvolatile dataflash memory a temperature sensor and RS 232 level converters for serial communications It can read voltages 0 5v and has a 32 KHz crystal for real time clock applications And as mentioned it can read a variable resistance where the light sensor was designed to be mounted The Butterfly s processor is an Atmel ATMegal69 8 bit RISC MCU reduced instruction set microcontroller unit powered by a 3 volt coin battery CR2450 The MCU includes 16K bytes of flash memory for program storage 1K bytes of static RAM for variable storage and 512 bytes of EEPROM for nonvolatile variable storage It has 3 timer counters an 8 channel 10 bit A D converter an analog comparator watchdog timer sleep modes and more The ATMegal169 datasheet see the Resources section details all the features As shipped the Butterfly is preloaded with a bootloader and an application demo program that shows off some of its tricks The batt
5. of numbers 1 to 6 will display Press the joystick in again and the process repeats The randomness of this program depends on how long you hold the joystick in counted to the microseconds There is no true randomness in a normal computer of course but this is a good way of faking it This program does not go to sleep so it will eventually run your Butterfly s battery down You will need to disconnect the power when you are not using it Or you can always reload the Butterfly s demo program if you wish or toggle the power to get back to the bootloader both of which do sleep Butterfly Tutorial C Baird Page 11 of 14 The Diceman Rolleth code 02000 0000 0001 0002 0003 0004 0005 0006 07 08 09 OA OB OC OD gt ie Orie Gero jaa a Won Orr EOL OFC 006025B044F04 064D024982C9A04 O0020E9F72224 01C09905C003950432C N w E0222E5AD00A94 097 O1F9 023E0022E06D002951CD025E0022E D047D0404E EBF OFEFODBFO00E8009361000027009 030 3B3 O2E03E0202 E66 9D00027000 ED0222437D 047 SEM OOZ IE CHES O5A DE ODACF1F922F 92BF 93AF935F93A591D8 1112422242394 Hil IQA eva NSIC Cis Se EEOB695A79508F437 SAIN LB AIS 064 008950F93FOE0E EOOF70000F Oo 00125 PEO FOE m H H H ERO EEE S E E S O EO Or OS O
6. the bootloader AVR Studio is pretty impatient and doesn t wait long to see the question marks from the bootloader If you aren t pressing the joystick in when you click the AVR Prog menu item AVR Studio is likely to tell you it cannot find the target board If it did not find the target board and you re pretty sure you have done things right and you passed the HyperTerminal test outlined above one possibility is that you are using a COM port that AVR Studio isn t trying This can especially happen if you are using a USB to serial converter as they sometimes assign high COM port numbers to the virtual serial port they install Look on Studio s Tools menu in the Options and increase the number of COM ports to try Butterfly Tutorial C Baird Page 8 of 14 Another trick that sometimes works is to just try it again Keep pressing the joystick in close out the nastygram about the unfound target board and click on AVR Prog menu choice again Once you see the AVRprog window click the Browse button and locate the hex file you wish to upload Ignore the Device frame and the Advanced button since you can t change the device or change the fuses using the Butterfly s bootloader With the hex file name in the textbox click the Flash frame s Program button Studio will erase program and verify the upload When you are done exit the window and AVR Studio unplug your Butterfly and it is ready to run its newly load
7. CD are you hint you shouldn t be We will assume this part worked and forge ahead Run AVR Studio It s a large program and takes a while to load Be sure your Butterfly is in the reset sleep state not running the demo You can toggle the power or choose the Jump to Bootloader option from the demo s menu While pressing the joystick in this will hurt your thumb click on AVR Prog marked Yes as shown in Photo 2 Butterfly Tutorial C Baird Page 7 of 14 File Project Build View Tools Debug Help rO Gz AVR Prog Trace Disabled recan Uber aces ICESO Selftest JTAGICE mkII Upgrade AVR ONE Upgrade AYRISP mkII Upgrade Yes AYR Dragon Upgrade STK600 Upgrade Customize Options Show Key Assignments Plug in Manager No Program AYR gt 4 FLIPS Information AVR Wireless Studio AYR Battery Studio exes Photo 2 Connecting to the serial bootloader The Program AVR selection marked No is used for ISP programming such as might be done using an STK500 It uses a completely different protocol than that expected by the Butterfly s serial bootloader The window shown in Photo 3 should appear oix r Hex file Browse Exit r Flash Verify Read EEPROM Program Verify Read Peon __ Vey a r Device ATmegal6 BOOT 7 Advanced Photo 3 AVR Studio sees
8. OS e r HHH HHH HHH H er o AO e O A a a 00250002331F04EE0140F0A95E9F701C O8F4F3950F9108954F934427063018F 43950650FBCF0295042B4F9108950F9254 1F921F9313E0012E11241A9471D015E 6EDO1F9I11F9ID0F9IND08950F930CE 00093E70007EB0093 E50000E10093E60 E80093 00 SSAA TS TTA 330B5B8381820C345C845 1 O5F8785861 E4000F910895BF93AF931F920E OF 931F9308940027001F112011F01A9 OF BCF102EBB27A0E2A20D0C90012004E O IL AL 2S Suet Lis ALCS AL AL LZ LALO ILS S AAAS B9F7002029F00024039402C000240A9 1F910F911F90AF91BF9108950605020165 EOD0A0916151211184068900028507 0522A51292B03537B797A042C547C562E16 083058805A32593 E365D35370FB4 0386088623A61393B13638BBC E0OF53 OF4 082 O7A O0C2 4C9 60D 487 8D3 ICO 0898A143C648C663E653D3F17678F8D8 lever S Syl ehS SHOES SAS AES FEOEO 083010F044E61DC0013051F068F010E E3E D16 125 amp Hj JMO E P O EE TE DAE O ey KO Ko Key eo Oe eyo ee E eyo ES eA G O Dh 021 0022 0023 0024 0025 2026 0000 C DFDOPRP RPP PEPE EP PPP RPP EP PPP PPP PP PP PPP PP PP Pep PP PE 018E 0OE10F08F4F39542 E0041610F04EE 001C048E0141629F020F441E0E10D08EF 0F395059108D04 0 ASSI D AT A A S ONT 0E8 029 423 IRONI 0169516951695C10F08F4D3950770089 DZT Gi
9. So Got a Butterfly Now What Chuck Baird avrfreaks net user name zbaird 2009 by Chuck Baird Table of contents PEG CULO a oes orada R NTA R 1 RCAWITES oio cesta ena e ede ea Slee ule aa Meta ardaee 2 The bootloader s siisii nEn A nl Ae 3 The demo application program ceeececssccecssececssececeeeeecseeeeceteeesseeeeees 3 Getting your Butterfly to do something eee eeeeceeeeeeeeesaeeneetees 4 But wait there S More oerna e SEEE E OTTEET 4 Adding some goodies to your Butterfly eeeeeecceceseeceeeeeeeteeeseteeeees 5 Programming uploading to the Butterfly eee eee eeeeeeeeeeereeeneeens 6 An AVR Studio Butterfly bootloader session eee eeeeeeeeeeneeeeeeees 7 Other programming Methods 0 eee eeeeceseeeeeceneceeeeseeeeaeessaeenseesees 9 THE AN R C00 stds tesa est E A Eaa 10 Assembly and C and other languages Oh MY uu eee eeeeeeeeeseeeeteees 10 Something to play with ci252 uks sigan gis eee aes 11 Butterfly and other resources 4 vocseecass evs sates east heroes eoeees 12 SUMMA eee e e a a a aee eah 14 Introduction This guide was written to help the novice user understand and appreciate the potential of the AVR Butterfly Atmel s demonstration and evaluation kit for their line of LCD capable 8 bit processors The term AVR allegedly means nothing more than a marketing term for the product line although it coincidentally happens to be the initials of the inventors At the time of t
10. ed program From this same programming window you can upload a hex file into EEPROM read the contents of either the flash or EEPROM memories the contents will be stored as a hex file or verify either memory against the indicated hex file Other programming methods It is unfortunate that the word programming has a dual meaning in the embedded world It means both to design and write code to perform a specific task and to upload code into the nonvolatile memory of the MCU For now we are interested in the second meaning and the first is covered briefly in a later section There is a nice tutorial by Dean Camera user name abcminiuser on the avrfreaks website see Resources that discusses the various programming methods and hardware available for programming most AVRs A serial bootloader is convenient because it doesn t require any specialized or additional hardware but it isn t used as often as some of the other methods On the Butterfly it also has the shortcoming of not being able to access the fuses and certain other parts of the MCU although this is limited by the design of the bootloader not the MCU itself ISP In System Programming is probably the most popular programming method and one that is available on the Butterfly With proper design it allows an MCU incorporated into an existing design that is in system to be programmed without removing the MCU chip from the circuit JTAG Joint Test Action Group is an
11. edded C The same is true for the other high level languages as well There are many compilers and assemblers available for the AVR line of MCUs AVR Studio mentioned earlier as a Windows AVR programming platform includes an assembler two actually and is free One of the most popular of the AVR C compilers is WinAVR a GCC port WinAVR can be configured as a plug in for AVR Studio so you can use it directly from Studio Something to play with Here is a hex file for a little program that simulates a pair of dice on the Butterfly You may highlight and copy the code right out of this pdf document then paste it into Notepad or some other word processor Clean up any extra characters like leading or trailing blanks that may have been introduced in the copy and paste Save it as an ASCII text file with a name you ll recognize perhaps dice hex Depending on which word processor you use you may find the name gets a txt extension added to it which you will probably want to remove Upload it to the Butterfly using AVR Studio Then when the Butterfly gets a reset it will once again be running the bootloader waiting for the joystick to be pressed up or in Press it up and this program will run Unfortunately this program also sits there like a lump waiting for you to press the joystick in When you do all the segments in a couple of character positions will light up while the dice are being shaken When you release the joystick a pair
12. emove the coin battery Momentary contact normally open Figure 3 Adding a reset switch Programming uploading to the Butterfly Let s assume that your BOOTRST fuse is set correctly and your Butterfly sleeps quietly until you press the joystick up Eventually you may want to try something else besides the demo application and that involves getting the bootloader to overlay the demo program with some other program perhaps one you wrote The program needs to be in a file format called Intel hex This is a method of encoding data in printable characters that are highly portable can be read by virtually all Butterfly Tutorial C Baird Page 6 of 14 computers and is the de facto standard for programming embedded MCUs All embedded compilers and assemblers generate Intel hex files as output either automatically or on request The Intel hex file for the Butterfly s demo program is available on the Atmel website so you can reload it if you wish The Butterfly s bootloader hex file is also there as well as a combined file that includes both You need a PC program to talk to the Butterfly s bootloader and pass it data and the commands needed to write that data to memory One such Windows program is AVR Studio available free from Atmel It is a very large download over 125 megabytes so if you do not have a high speed internet connection it is worth finding one and burning the installation file to a CD T
13. ery is included but has a cardboard Butterfly Tutorial C Baird Page 2 of 14 spacer which prevents battery drain prior to it reaching the end user Removing the cardboard spacer should bring your Butterfly to life although it may not appear to do anything until you press the joystick up and wake it from its nap See the section below Getting your Butterfly to do something The bootloader A bootloader is a small program that can accept input usually a ready to run program from some source and write it into the memory of the computer the bootloader is running on Typically a bootloader will either automatically or in response to some command jump to execute the new program after it writes it to memory The name comes from the phrase to lift yourself up by the bootstraps an idiom of unknown origin describing an impossibility but meaning to improve your situation by your own efforts It was borrowed by the early computer geeks to mean getting a tiny program started which progressively brings in a larger program and is the origin of the phrase to boot a computer The Butterfly comes with a preloaded serial bootloader program It also comes with a preloaded demo application a separate program The two programs reside in different parts of the ATMegal169 s flash memory The Butterfly s bootloader is called a serial bootloader because it receives its commands and code to write to memory from the serial or RS 232
14. guidelines and observe posting etiquette when posting or someone will likely toast your buns Do your homework first search the avrfreaks site and use Google and read up on your topic prior to posting I can be contacted via private message PM through avrfreaks user name zbaird I reserve the right to tell you to post your question as a new thread if I feel it is of general interest or value for the community at large or refer you to some of the resources mentioned here Another AVR user community is at http www avrbeginners net although it is primarily oriented toward assembly language programming It also has valuable tutorials examples and links An avid and esteemed avrfreak is Joe Pardue author of a couple of books on AVR programming Through his website at http www smileymicros com he has put together several bundles of projects and parts with and without books Any Butterfly you buy from him is assured to have its fuses set correctly and he stands behind what he sells and will make sure you are happy Joe is writing an ongoing series of articles on programming the Butterfly and Arduino using C They appear in Nuts and Volts a monthly magazine but he also posts past articles on his website under the name Smiley s Workshop They provide a good introduction to AVRs the Butterfly and the Arduino Other distributors of Butterflies are Digikey Arrow and Mouser in the U S and others in Europe and elsewhere tha
15. here are other programs both for Windows and other operating systems but here we will only consider AVR Studio An AVR Studio Butterfly bootloader session Here we describe how to upload program burn a new program into the Butterfly s flash memory using AVR Studio and the Butterfly s serial bootloader As mentioned you may also restore the original demo program using this technique You will need to have a copy of the Intel hex file you want to upload and be able to tell AVR Studio where it is Install AVR Studio Plug your newly added Butterfly s serial connector into your PC s serial port or your USB to serial converter You may need a straight through not a null modem cable to have enough wire length to make this connection Turn on your Butterfly You can test your Butterfly s connection by running a terminal program such as HyperTerminal configuring its serial port to a baud rate of 19200 8 data bits and either 1 or 2 stop bits When you press the Butterfly s joystick in from the sleep state not while the demo is running you should see a stream of question marks received by HyperTerminal This is the bootloader trying to connect to the host software If you cannot receive the question marks there is little use in trying to connect to AVR Studio Check your connection wiring and COM port selection and parameters Remove and reapply power to the Butterfly You are not seeing the scrolling banner on the L
16. hine language instruction can be thought of as a series of Os and 1s which when encountered by the processor cause a certain action to be taken Ultimately all computers languages result in a series of machine language instructions because they are the only things the MCU understands Assembly language is a set of mnemonics that make it easier for humans and programmers to generate those Os and 1s Usually a single line of assembly language results in a single machine language instruction Higher level languages like C C BASIC PASCAL and so on are made up of statements Each statement may result in one to perhaps dozens of machine language instructions Butterfly Tutorial C Baird Page 10 of 14 An assembler is a computer program that converts assembly language to machine language A compiler is a computer program that converts a high level language to either assembly language or machine language With most compilers you can view the assembly language output to see how it has done the translation from the high level language C is probably the most popular programming language in the embedded world A C standard does exist and all compilers adhere to it as much as possible Embedded microcontrollers however present special challenges and requirements that exist outside the standard Each compiler resolves these issues in the ways of their writers choice so there are small syntactical differences between each dialect of emb
17. his writing the Butterfly retails for about 20 in the United States We will take a look at the Butterfly board and its complement of peripherals the microcontroller that provides its smarts how to upload new programs into it and some of the documentation and support resources that are available for it We will only be able to touch the high points to get you started there is much more that we will omit but which you can discover with a little searching and digging Always remember Google is your friend If this is your first foray into the world of embedded computing enjoy the trip These small general purpose computers are ubiquitous assisting you hundreds of times a day in ways you never dream of The Butterfly will give you a glimpse into their array of capabilities Butterfly Tutorial C Baird Page 1 of 14 Features Photo 1 shows the front view of an older model Butterfly when they were shipped with a light sensor an LDR or photo resistor shown in the upper left hand corner Because of ROHS restrictions against cadmium the sensor is no longer mounted although you are certainly free to add one yourself since all the support circuitry is still included The small holes around the left and bottom edges of the board are for connecting various external circuits to the Butterfly They use 0 1 spacing so standard headers may be soldered in or wires can be soldered directly to the board However nothing external has to
18. ies to your Butterfly If you want to use the serial line to input data names into the demo application or if you want to use the Butterfly s serial bootloader to load a different program you will need to add a connector to your Butterfly This may be soldered directly on the board or you may use 0 1 headers and have the ability to unplug it when it is not in use Of course you will then need to make sure you orient it correctly when you plug it in You may also wish to make a battery power supply using two AA cells or C cells or D cells to use in place of the coin battery that comes with the Butterfly You will find that using the RS 232 interface will run your coin battery down fairly quickly If you choose to make an external power supply you may put a switch on it to provide an easy way of doing a reset and killing power when the Butterfly is not in use The sleep modes are low power but they re not zero power And if you want to go whole hog you can even add a reset pushbutton All of this is described in excruciating detail in the link labeled Appendix A on my website at http www zbaird com The Reader s Digest condensed version is shown in the following three diagrams Butterfly Tutorial C Baird Page 5 of 14 Female DB 9 Connector Rear View facing solder cups Figure 1 Adding an RS 232 connector Positive Negative Gnd Figure 2 Adding a 3v battery power supply r
19. med one way a reset jumps to the application section If it is programmed the other way a reset jumps to the bootloader section It is our responsibility to have previous loaded code at the proper address for the way we have set the fuse s Perhaps needless to say the Butterfly s serial bootloader has been preloaded into the bootloader section of memory and the demo application has been preloaded into the application section The BOOTRST fuse has been programmed to make a reset jump to and execute the bootloader or at least it should be The bootloader needs to know whether you are wanting to upload a new application or run the existing application On the Butterfly the one source of easy user input is the joystick so the bootloader waits for you to press the joystick up jump to the application or in start uploading a new application using the serial communications line If it doesn t see either joystick press within a certain amount of time it goes to sleep That is it stops executing instructions and enters a low power mode To you the casual observer this means the Butterfly just appears to sit there like a lump It will continue to sit there until you press the joystick up or in Doing either will wake it out of its sleep mode and cause it to take the appropriate action But wait there s more Let s say you press the joystick up meaning you would like to run the existing application the demo unless you have loaded so
20. mething else After some initialization that takes a second or two the demo program starts scrolling a banner message across the LCD waiting for further joystick input which navigates you through the menu structure Butterfly Tutorial C Baird Page 4 of 14 When you see the banner the bootloader is no longer executing and the demo program is in control One of the menu choices on the demo program is to jump to the bootloader and if you choose it you will execute a reset At that point the entire process starts all over from the beginning And now for the bad news If your Butterfly immediately within a second or two shows the scrolling banner on power up or reset then either the BOOTRST fuse is set incorrectly or the bootloader is missing or both In early 2009 Atmel shipped some Butterflies with the BOOTRST fuse incorrectly programmed although they were supposed to have been recalled If your fresh from the box Butterfly comes to life magically by itself and displays the banner without you pushing the joystick up you have one of these units If you have an incorrectly programmed BOOTRST fuse you may exchange your Butterfly find someone with the hardware programmer needed to fix the fuse or invest in the hardware yourself Even if you could run the serial bootloader somehow you can t it is unfortunately incapable of changing that fuse itself It takes the intervention of a Deus ex Machina to save the day Adding some good
21. other method of programming that is available on the Butterfly Originally developed for testing complex circuit boards after assembly it has been extended to allow full access and control of the processor during execution This means that for those AVRs that support JTAG the processor can be single stepped have registers and memory examined and modified breakpoints added and removed and so on while the processor is running This obviously allows interactive on chip debugging as well as programming the flash memory High voltage programming is another technique supported by most AVRs although the Butterfly is not designed to take advantage of it Butterfly Tutorial C Baird Page 9 of 14 The AVR core One of the nice things about the AVR product line is that almost all of the MCUs use the same processor core with some minor variations Individual models may vary in speed power consumption peripherals number of I O bits size of the three kinds of memories and so on but the instruction set and general programming considerations are more or less the same Once you have learned to program one AVR you know a lot about all of them There are specialty lines within the larger AVR world models that have built in USB support LCD support like the Butterfly s ATMegal69 CAN bus automotive support and so on Again other than the addition of the specialty peripherals the basics of the processors themselves are virtually identical
22. r OU Ze tn O OAC SHE CuO Sicdi 277 OLE 019F41095012301C0012B0883CF91DF9180 O0895FF EF 91LFF910895DF93CF93D0EOCCEE102FA4 476 Listing 1 Dice simulation Butterfly and other resources The Atmel website http www atmel com is the place to start for anything related to AVRs and or Atmel products Here you will find The Butterfly Quick Start Guide The Butterfly User Manual includes schematics The bootloader hex file ready to be uploaded The demo application hex file ready to be uploaded The combined bootloader and demo hex file ready to be uploaded The AVR Studio program The ATMegal169 datasheet summary and complete versions Butterfly Tutorial C Baird Page 12 of 14 Numerous application notes Other datasheets and documentation The assembly language instruction set manual And much much more Use the search feature of the website to locate these things since they could move around The search term Butterfly is a good starting place The AVR Studio help files contain a wealth of information about all sorts of things Have a look through them The AVR user community at http www avrfreaks net is another extensive resource It is very active and full of knowledgeable people who are eager to help Be sure to check out the projects and tutorial sections Of particular interest is stu_san s Newbie Start here thread in the sticky section of the AVR forum Please read the
23. t can be found with your friend Google s help At the time of Butterfly Tutorial C Baird Page 13 of 14 this writing at least a few Butterflies from these sources were being shipped with incorrectly set fuses although hopefully by the time you read this it will all be ancient history Software for development compilers assemblers programmers are available in several flavors from several sources While C and assembly language are the most common you can also program AVRs in BASIC and FORTH and probably other languages I do not know of an AVR COBOL compiler sorry AVR Studio which includes an assembler and extensive programmer support and can interface with the GCC WinAVR and ImageCraft C compilers is available free from Atmel WinAVR is free while ImageCraft and most of the other commercial C compilers have free demo or trial versions that have some time or size limitations There are many many sources of development boards for the AVR product line The Arduino line is reportedly very easy to use and is AVR based Everyone and his dog sells some specialty board built around some AVR MCU or another Atmel has a line of development boards and programmers the STK500 STK600 Dragon JTAGICE MK2 and so on Summary So have at it Of course this has been the briefest of summaries so most likely you will need to follow up by researching additional information for your topics of interest If you have never worked with embedded s
24. ystems before and you are interested in exploring programming expect the learning curve to seem a little steep at times However as the J Ching says perseverance furthers Stick with it do some reading ask some questions learn from your failures enjoy some successes and plow ahead Before you know it you will be an old pro and have the battle scars to prove it Good luck Butterfly Tutorial C Baird Page 14 of 14
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