Arduino UNO FAQ

There's so many Arduino's out there, it may get a little confusing. We wanted to clarify for people some of the changes in the latest version.

NB this is just our opinion and interpretation of some of the decisions made by Arduino. We aren't associated with Arduino, and don't speak for them! If you have to get an Official Response to your Arduino question please contact them directly. Thx!

NB2 Still in progress, we're collecting common questions to answer. If you have more questions, please post them in our forums.

Arduino Timeline

But first…some history! First there was the serial Arduino (what's the name of it?) with RS232 which was not used outside of the Arduino team & friends.

The first popularly manufactured Arduino was called the NG (New Generation, like Star Trek, yknow?) The NG used the Atmega8 chip running at 16 MHz and an FT232 chip for the USB interface. The bootloader takes up 2KB of space and runs at 19200 baud.

The next version was the Diecimila. The Diecimila updated the chip from the Atmega8 to the Atmega168. The great thing here is double the space and memory (16K instead of 8K). It still ran at 16MHz. The Diecimila also added two extra header pins for 3.3V (from the FTDI chip) and the reset pin which can be handy when a shield is covering up the Reset button. The bootloader takes up 2KB of space and runs at 19200 baud. Auto-resetting was also added which makes life awesomer for everyone.

In 2009, the Duemilanove was released. This one also upgraded the chip again, to the Atmega328. Yet another doubling of space and memory! Another upgrade is now the power is automagically switched between USB and DC-jack which removed the previous jumper. This makes it easier and faster to move from programming to standalone and got rid of some confusion. The bootloader takes up 2KB of space and runs at 57600 baud.  

In 2010, we have the Uno! The Uno still uses the 328P chip and the power switcher. It has a smaller bootloader called OptiBoot (more space for users' projects) that runs at 115K. So even though the chip is the same, you get another 1.5K of extra flash space that was previously used by the bootloader. The FTDI chip has also been replaced with a atmega8u2 which allows for different kinds of USB interfaces. Finally, there's an extra 3.3V regulator (LP2985) for a better 3.3V supply. whew!

New USB Chip

So! All of the older Arduinos (NG, Diecimila and Duemilanove) have used an FTDI chip (the FT232RL) to convert the TTL serial from the Arduino chip (Atmel ATmega). This allows for printable debugging, connecting to software like PureData/Max, Processing, Python, etc. etc. It also allows updating the firmware via the serial bootloader.

The good news about the FT232RL has royalty-free drivers and pretty much just works. The bad news is that it can -only- act as a USB/Serial port. It can't act like a keyboard, mouse, disk drive, MIDI device, etc.
The Uno has changed that by exchanging the FT232RL chip with an atmega8u2 chip. There are a few things that are possible with this new chip but before we discuss that lets make it clear that by default, this chip acts identically to the FTDI chip that it replaces. It's just a USB-serial port!

One improvement in updating the chip is that, previously, Mac users needed to install FTDI drivers. The 8u2 imitates a 'generic' CDC serial device. So now, Mac users do not have to install a driver. Windows users still need to install the .INF file but luckily there are no drivers. This means there will be fewer problems with new versions of windows. There is no way to have a serial USB device that doesn't require an INF file in windows, sadly :(

The big thing that is nice about the 8u2 is that advanced users can turn it into a different kind of USB device. For example it can act like a keyboard or mouse. Or a disk driver. Or a MIDI interface, etc. Right now there are no examples of how to do this, but we hope to post some shortly.

And, finally, going with the 8u2 reduced the price of the board which made up for some of the other extras.

Why not just go with a atmega32u4?

The Arduino team has indicated they thought about this but preferred that hackability of a DIP chip.

Right now there are a few Arduino's with a 32u4 chip such as the Leonardo, Micro and Esplora

How can I change the USB firmware?

The 8u2 can be programmed by soldering a 6-pin ISP header (the R3 has the 6-pin header pre-soldered in) and using a standard AVR programmer. You can also use the bootloader (DFU) in the 8u2. On first generation Unos, you enable this by soldering the 10K resistor right underneath the board. (R2 and R3 versions of the Uno use the 16U2 and do not require the resistor!) Again, we don't have any examples or tutorials but hope to shortly.
The code for the 8u2 is based on LUFA, Dean Cameran's totally awesome USB-AVR library that has great examples and documentation. Its also completely open source.

Does the Uno use a resonator or a crystal for the processor clock?

The FT232RL had an internal oscillator whereas the 8u2 does not. That means there is a 16mhz crystal next to the 8u2 to allow it to keep up with precise USB timing.

On the other hand, the Atmega328p chip that is the core processor in the Arduino now has a 16mhz ceramic resonator. Ceramic resonators are slightly less precise than crystals but we have been assured that this one was specified and works quite well.

So the Arduino is not as precise, timing-wise?

The short answer is: yes. The long answer is that most things that people are doing with Arduino do not rely on 20ppm precision timing where 100ppm would fail. For people who want long term precise timekeeping we suggest going with a TCXO (temperature compensation crystal oscillator) - but you would know if you needed that.

Why not have one 16Mhz crystal shared between both?

Good question, technically you can. However, in practice the board did not make it through FCC certification with one crystal (long traces with fast squarewaves = lots of noise).

OK well lets say I don't care about that...

You can absolutely connect the CLKO out the crystal from the '8u2 to the '328p but you're on your own as we don't think there will be any tutorials about that.

Whats with the FCC logo on the back?

Arduino is now FCC certified! That means that the board by itself passes FCC certification for electromagnetic emissions. It does not mean that your project is FCC certified. The moment you change the Arduino, it's no longer FCC certified (although we'd like some back-up documentation on this).
It is also, still, CE certified for Europeans.

A new Bootloader?

There's a new bootloader. It works just like the old one - being an STK500-protocol compatible but its a quarter of the size! Down from 2K, the new bootloader is a tiny 512b. This gives you more space for your project code! Yay! It's also faster - 115K instead of 57.6k so you'll be uploading code in 3 seconds.

The Bad News is that you must make sure to select Uno in the Boards menu!!! If you don't things will be confusing because the bootloader speed is wrong, and you won't get that extra 1.5K!

Overall, its a good direction, and the chips can be used in older Arduinos just fine (so you can upgrade your Diecimila or Duemilanove to the Uno by simply replacing the chip).

For more detailed information about the bootloader, such as source code, please visit the Optiboot project page.

Why not just use the '8u2 as a programmer?

While it is possible that the 8u2 could act as a full ISP programmer there are a few reasons why its good that it isn't.
  1. Giving beginners access to a full ISP programmer will result in bricked chips. There's no risk of messing up the Arduino chip beyond recognition if it's just being bootloaded
  2. Having the chip act only as a USB/serial passthrough simplifies the firmware so that the chip has only one function instead of having to have it do double duty as programmer -and- serial interface (think about it, its not easy)
  3. Backwards compatibility - the Arduino chips can still be programmed with FTDI breakout boards or cables, making it easy for people to breadboard or make clones.

How does the new '8u2 affect Arduino-derivatives?

Every USB device needs to have a unique product id and vendor id. Vendor IDs (VID) are sold to companies and Product IDs (PID) are chosen by that company. So for example FTDI owns VID #0403 and they give their chips ID's between #0000 and #FFFF (65,536 different PIDs) Older Ardiuno's used FTDI's VID/PID as that is part of the deal when you purchase their chips. Because the Uno does not use an FTDI chip anymore, the Arduino team had to purchase a USB Vendor ID (VID). Every Arduino product will now have their own PID starting with the Uno (#0001).

If you want to make your own Arduino-compatible board, you have a few choices:
  1. Don't use an 8u2, go with an FTDI chip instead that comes with a VID
  2. If you're planning to make more than one board for your personal use, you will have to purchase a VID from USB IF for a one time $2000 fee
  3. If you're making a single board for your own experimentation, you can pick a VID/PID that doesn't interfere with any devices on your computer and substitute those in
  4. You can purchase licenses for single VID/PID pairs from companies that develop USB devices (we dont have any specific links at the moment)
However, you can't use the Arduino VID when distributing your own Arduino-compatibles! If the cost of a VID is too much for you, simply go with an FTDI chip, K?

I tried to find a place to buy some '8u2s and couldnt locate any!

Yep, there is a worldwide shortage of Atmel parts right now. Even the chip used in the Arduino core (Atmega328P) is really hard to get. This happens after recesssions. We hope that these and other Atmel chips will show up again in places like digikey soon. Till then, keep searching on findchips.com!

So does this mean there may be an Arduino shortage?

Probably not. The Arduino team buys chips in the 10's of thousands, directly from Atmel. They probably get priority over distributors because of this. We're assuming the team bought enough to last for a while.

Did the Arduino team move from the FTDI chip to the '8u2 to screw over derivative-makers?

While the appearance of a hard-to-get chip coupled with the VID/PID mishegas may seem to be a little annoying, we don't think that means that the Arduino team is being malicious or attempting to make life difficult for people who make derivatives. The move to an '8u2 makes the Arduino more powerful, and easy to use as there are fewer drivers to install. While there is a shortage now, there will eventually be plenty of chips on the market.

Some people in the Arduino forum have thought of forming a group that would purchase a VID for Arduinites to use in personal projects. This is a pretty good idea and its probably the best way to avoid VID/PID conflicts. Between 65,536 projects, that comes to under a nickel per PID.

And of course, because they didn't get rid of the bootloader system, you can always just use an FTDI chip.

Are Shields still going to work?

All previous shields should still work perfectly fine as the header spacing is the same, the core chip is the same and the location of parts is the same. In fact, some should work better because the 3V supply has been upgraded (see next point).

Will enclosures, plates, etc still work?

Yup! The Uno is physicially the same size and layout as previous Arduinos. The mounting holes are in the same location. There is an additional mounting hole as well, now.

More 3.3v power!

One sad thing about older boards is that they had a 3.3v power supply but it was really just whatever the FTDI chip's internal 3.3v regulator could give. You -could- get 50mA out of it, maybe. But high power stuff like XBees, SD cards, some fast ADC or DACs could easily drag down the FTDI chip and reset the USB connection. The Uno solves this problem by adding a new 3.3V regulator the LP2985 which can easily provide 150mA.

The LP2985 is a very high quality regulator, and will work great for powering stuff and as a nice solid 1% analog reference.

Why is the Arduino chip running at 16MHz when it can run at 20MHz?

This is a common question. The reason is that the first Arduino used the Atmega8 which could not run faster than 16Mhz. As the chip has been upgraded they wanted to make the boards speed compatible. Arduino is also not really intended for fast-processing (its only 8-bit anyways) so the chips are running at 16MHz.

Is it still Open source hardware and software?

Yes! The Uno is still available under a Creative commons license. You can get the latest schematics and layouts over at the Arduino website.

UNO R2 and R3

During fall of 2011, the Arduino team revealed that there will be a new minor revision of the classic Arduino, the "UNO R3" (revision 3). A lot of people have asked us about the R3 so here is everything we know so far.
  1. The UNO R3 is not available to resellers until December 1st or so. Really! Nobody has them until then!
  2. The UNO R3 is backwards compatible with the UNO - same driver, same uploading, same look
There are a few changes in the UNO, here is what they are:
  1. The USB controller chip has moved from an atmega8u2 (8K flash) to an atmega16u2 (16K flash). This does not mean that you have more flash or RAM for your sketches this upgrade is for the USB interface chip only. In theory this will mean that it will be easier to have low level USB interfaces such as MIDI/Joystick/Keyboard available. However these are only theoretical at this time, there is no example code or firmware which will actually do this.
  2. There are three more breakout pins on the PCB, next to the AREF pin there is are two I2C pins (SDA/SCL) - this is a duplication of the Analog 4 and 5 pins. There is not an extra I2C interface or anything, its just that they made a copy of those pins there for future shields since the I2C pins are in a different place on Mega. There is also an IOREF pin which is next to the Reset pin - this is to let shields know what the running I/O pin voltage is on the board (for the UNO, its 5V). Again, this is a duplication of the power pin, it does not add voltage level shifting to the UNO.
  3. The RESET button has moved to be next to the USB connector, this makes it easier to press when a shield is on top.
Here is what didn't change in the UNO:
  1. Processor size and speed - its the same ATMega328P running at 16MHz that we've had since the Duemilanove. Your code will not run faster or better on the R3
  2. Same number of pins - no extra pins are added EVEN THOUGH THERE ARE MORE BREAKOUTS (see above!)
  3. Board size and shape - same size as before
  4. Shield compatibility - Every shield that works and plugs into the UNO R1/R2 should be able to work fine with the R3
  5. Driver - the driver is the same
  6. Upload speed - same upload speed and technique
If you want to get up an Arduino R3 now, visit the adafruit store and pick up a board or pack!

Arduino Libraries

Need Help Installing a Library?

Check out our super-detailed tutorial for all operating systems here:
http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use

What is a library?

Libraries are great places, and not yet illegal in the United States! If you ever need to learn how to do something, like say fix a motorcycle, you can go to your local library and take out a book. Sure you could buy the book but the library is nice because as a resource you can get the book whenever you need it, keeping your house uncluttered.

Software Libraries are very similar. We already studied what a procedure is, in lesson 3: a procedure is a list of things to do. A library is a big collection of procedures, where all the procedures are related! If you, say, want to control a motor, you may want to find a Motor Control Library: a collection of procedures that have already been written for you that you can use without having to do the dirty work of learning the nuances of motors.

For example, this is the Serial Library, which allows the Arduino to send data back to the computer:

Using Libraries

One of the best features of the Arduino project is the ability to add on pre-crafted libraries that add hardware support. There's tons of them, and you can pick and choose which to install. They're only loaded in when the sketch you're working on needs them, so for the most part you can download and stash them for future use.

Sketches will often depend on libraries, you can see what they are by looking at the top of the sketch. If you see something like:
#include <FatReader.h>
That means that you'll need a library called FatReader or a library that contains the file FatReader. If you dont have it installed you'll get an error:

What's in a library?

A library is a folder with some files in it, the files will end in .cpp (C++ code file) and .h (C++ header file).
There may also be some .o files. The .o files are C++ compiled Objects. If you end up working on the library and modifying it, be sure to delete the .o files as that will force the Arduino IDE to recompile the modified .cpp's into fresh .o's.

Two optional files you may see are keywords.txt (this is a hints file to tell the Arduino IDE how to colorize your sketch and examples folder, which may have some handy test-sketches. These will show up under the File→Examples→Library dropdown.

It's important to remember!

The structure of the library folder is very important! The .c and .h files must be in the 'lowest level' of folders. For example, you cant have Arduino/libraries/WaveHC/WaveHC/file.c or Arduino/libraries/MyLibraries/WaveHC/file.c - it must be Arduino/libraries/WaveHC/file.c

How to install libraries

In Arduino v16 and earlier, libraries were stored in the ArduinoInstallDirectory/hardware/libraries folder, which also contained all the built-in libraries (like Wire and Serial).

In v17 and up, the user libraries are now stored in the ArduinoSketchDirectory/libraries folder. You may need to make the libraries sub-folder the first time. However, the good thing about this is you wont have to move & reinstall your libraries every time you upgrade the software.

For example, here is how it looks when NewSoftSerial is installed in Windows (of course your username will be different).
On a Mac, your arduino sketch folder is likely going to be called Documents/arduino so create a NEW FOLDER inside that called libraries and place the uncompressed library folder inside of that.

Check that the Documents/arduino/libraries/MyNewLibary folder contains the .cpp and .h files.

After you're done, restart the Arduino IDE.

Bootloader

This is some advanced bootloader tweaks - 99% of Arduino users should not mess with their bootloader! Only for the wild at heart!

Bootloader for the Atmega328

Here is the package for a 'fixed up' ATmega328 bootloader. To program it you may need to change the Makefile's ISPTOOL, etc definitions. The commands are make adaboot328; make TARGET=adaboot328 isp328 (I couldn't get the default 'isp' target to work so I made a new one).

This version has a few fixes: first it integrates the 'no-wait' and 'no-hang' fixes below. It also fixes the annoying "missing signature bytes" bug that freaks out avrdude when programming without the IDE. I also repaired the EEPROM code so that now you can upload and download the EEPROM memory as well as flash. Finally, theres a 'upload feedback' using the LED, for arduino clones that don't have TX/RX leds.

Please note that the fuses are different for this chip because of the extended memory!

"No-Wait" Bootloader

Here's a bootloader hack that will automatically start the sketch after it has been uploaded and will also only start the bootloader when the reset button is pressed (so when you plug in power it will go straight to the sketch).

Copy the following lines:
ch = MCUSR;
    MCUSR = 0;

    WDTCSR |= _BV(WDCE) | _BV(WDE);
    WDTCSR = 0;

    // Check if the WDT was used to reset, in which case we dont bootload and skip straight to the code. woot.
    if (! (ch &  _BV(EXTRF))) // if its a not an external reset...
      app_start();  // skip bootloader
And paste them as shown:
/* main program starts here */
int main(void)
{
    uint8_t ch,ch2;
    uint16_t w;

    ch = MCUSR;
    MCUSR = 0;

    WDTCSR |= _BV(WDCE) | _BV(WDE);
    WDTCSR = 0;

    // Check if the WDT was used to reset, in which case we dont bootload and skip straight to the code. woot.
    if (! (ch &  _BV(EXTRF))) // if its a not an external reset...
      app_start();  // skip bootloader

    /* set pin direction for bootloader pin and enable pullup */
    /* for ATmega128, two pins need to be initialized */
Now, in the same way, copy the following code:
// autoreset via watchdog (sneaky!)
	  WDTCSR = _BV(WDE);
	  while (1); // 16 ms
And paste it here:
/* Leave programming mode  */
	else if(ch=='Q') {
	  nothing_response();

	  // autoreset via watchdog (sneaky!)
	  WDTCSR = _BV(WDE);
	  while (1); // 16 ms
	}
	/* Erase device, don't care as we will erase one page at a time anyway.  */
	else if(ch=='R') {
	    nothing_response();
	}
You can also just grab the source code and compiled hex file here.

It will work in NG or Diecimila Arduinos.

No-Hang Bootloader

If you are using a Diecimila with auto-reset you may be frustrated when your communications program accidentally triggers the bootloader. Here is a quick hack to make the bootloader quit if it doesn't receive a '0' character first (which would indicate the Arduino software is trying to talk to it.

Copy the following line:
uint8_t firstchar = 0;
And paste:
/* main program starts here */
int main(void)
{
    uint8_t ch,ch2;
    uint16_t w;
    uint8_t firstchar = 0;
Copy:
firstchar = 1; // we got an appropriate bootloader instruction
Paste:
/* Hello is anyone home ? */ 
	if(ch=='0') {
	  firstchar = 1; // we got an appropriate bootloader instruction
	  nothing_response();
Then paste this below the above code:
} else if (firstchar == 0) {
	  // the first character we got is not '0', lets bail!
	  // autoreset via watchdog (sneaky!)
	  WDTCSR = _BV(WDE);
	  while (1); // 16 ms
	}
You can also just replace the last two lines with app_start()

Upload Sketches with AVRDUDE

The bootloader is an 'stk500'-compatible, which means you can use good ol' AVRDUDE to program the arduino.

Just plug in the USB cable, then press the reset just before you start avrdude. If you need an avrdude tutorial, check out this page.
  • Use -b 19200 to set the baud rate to 19200
  • The device signature reads dont seem to work so you'll want to use -F
  • The programmer type is avrisp
  • The device type is -p m168
  • The port is whatever the FTDI chip shows up as

Upgrade

Introduction

The 'brains' of the Arduino is a microcontroller called an ATmega. It is a product line from ATMEL (a Norweigen chip company). Just like Intel & AMD release new & better chips each year, so does Atmel. The first versions of the Arduino (up to the NG) used an ATmega8 - a chip with 8K of flash memory and 1K of RAM. Then Atmel released the ATmega168, a drop-in replacement with 16K of flash and 1K of RAM - a really big improvement! Now there is the ATmega328 with 32K of flash and 2K of RAM.

Updating and replacing your Arduino is easy and painless and costs only a few dollars. Your sketches will work just as before but with a little more breathing room.

In order to perform this upgrade you will have to either purchase a preprogrammed chip or program it yourself with a AVR programmer or by 'bitbanging' it.

Replace the Chip

First, gently pry the Arduino microcontroller from its socket using a small flat screwdriver or similar. Try to make sure the pins dont get bent. Put it in a safe place. Preferably in an anti-static bag.
Next, prepare the new chip. The pins of ICs are a little skewed when they come from the factory, so they need to be bent in just a tiny bit, to be parallel. Grip the chip from the ends and use a table.
Finally, replace the old chip, lining up all the pins and making sure that the notch in the chip matches the notch in the socket!

Download an Arduino IDE with ATmega328 compatibility

Version 13 and up of the Arduino software supports the 328!

If you purchased a chip from Adafruit that shipped before Feb 5, 2009 the chip will have the baudrate set at 19200 (same as the older Arduinos). After Feb 5 the upgrade chips were changed to 57600 baud rate (3 times faster!) in order to be compatible with new Arduinos. If you have a 19200 baud rate chip you will have difficulty uploading. Simply quit the Arduino application and edit the file in the hardware folder named boards.txt and change the line from:
atmega328.upload.speed=57600
to:
atmega328.upload.speed=19200
If you're having problems please try BOTH just in case!

3.3V Conversion

Introduction

All official Arduinos run on 5 volts, which for a long time was the 'standard' voltage for hobbyist electronics and microcontrollers. But now the coolest new sensors, displays and chips are 3.3V and are not 5V compatible. For example, XBee radios, and SD cards and acellerometers all run on 3.3V logic and power. If you tried to connect to them with 5V you could damage the internals of the accessory.

We use chips like the CD4050 to do level conversion but if you are using a lot of 3.3V devices, maybe you're just better off upgrading the entire Arduino to run from 3.3V!

To do that, we will replace the regulator so that the DC barrel jack goes to a 3.3v type regulator, not a 5V. And then reconfigure the 5V usb power line so it goes through the regulator as well.

Replace the Regulator

The default regulator is a 5.0V type, but we want 3.3V out, so we'll need to replace it. We'll use a 1117-3.3V (there are a few manufacturers of 1117 regulators, just like the 7805 is made by many factories) regulator in a TO-252-3 package. It looks like this:
You can get these from any electronics component shop, for example here is the digikey link.

To start, we'll need to remove the old regulator. The easiest way to do that is to first clip the two legs.
Then you'll need to heat the tab up to get it liquid so you can lift off the old part. Although it may seem counter intuitive, its best to add some solder to the tab, melt it on with your iron, this will improve the heat conduction since the tab is so large.
Clean up the tabs and remove any clipped parts still stuck on.
Now line up the new 3.3V regulator, and solder the tab first, use plenty of solder and be patient, the tab acts like a heat sink.
Then do the two legs.

Replacing the Fuse

The next part is a little tricky, the USB jack gives us exactly 5V already, and normally that is tied to the output of the voltage regulator (essentially, its got a little circuitry that connects it when the DC jack is not powered).

The easiest way to make the USB 5V also go through the regulator is to remove the fuse and solder a diode from the USB output to the regulator input.

You can use any power diode, a 1N4001 is perfect and only a few pennies.

The trade off is now there is no 500 mA fuse for the USB jack. The good news is that computers will have their own fuses on the USB connector (inside the computer) so its not likely you will destroy your PC. But be aware that you're losing a little safety.

Heat the fuse with your soldering iron, again adding solder may help thermal conductivity. Since the fuse is very conductive you can probably just heat one side for a while and both ends will melt.
Clip the diode short and bend the leads over. Solder the side without a stripe (anode) to the old fuse pad, nearest the board edge. Solder the striped end (cathode) to the right hand leg of the regulator.

The Arduino will still automatically select whichever power plug is giving you more power.
That's it! You are now 3.3V powered. This is a little lower than the power/frequency specification for the AVR chips since they ought to have about 3.6V to run 16Mhz but its probably not going to be an issue since AVRs can be overclocked a little.

Arduino Hacks

Bumpers

Having the conductive traces touch your table is not so great, you can protect your Arduino by adding bumpers to the bottom.
You can buy these from McMaster Carr part no. 95495K66 (in large quantities) or Adafruit

Free up some RAM

If you're working on a project that needs a lot of memory, you can free up 100 more bytes (10% of the RAM on an ATmega168!) by lessening the serial receive buffer. By default its 128 bytes, which is quite a bit!

Open up hardware/cores/arduino (or cores/arduino) directory, and edit the file named wiring_serial.c or HardwareSerial.cpp

Near the top is a #define RX_BUFFER_SIZE 128, which means 128 bytes are used for the buffer. You can change this to 32 (or even 16!). If you have almost no serial input, make it as low as you'd like as long as its > 0.
You can also save another 2 bytes by changing rx_buffer_head and rx_buffer_tail from int to uint8_t

ArduinoISP

Introduction

A lot of people start learning about microcontrollers with an Arduino but then want to build their own projects without having to sacrifice their dev board. Or maybe they want to make their own Arduino variant, that is compatible with the IDE. Either way, a common problem is how to burn the bootloader onto the fresh AVR chip. Since AVRs come blank, they need to be set up to be Arduino IDE compatible but to do that you need an AVR programmer (like the USBtinyISP).

The good news is that you can burn bootloader using your existing Arduino with only a little bit of work. There's even a minitutorial on the arduino.cc site.

This tutorial is an extention of that tutorial. First we'll show how you can make a permanent bootloader-burner by soldering a 28-pin ZIF socket to a proto shield and use the PWM output line of the Arduino to generate a clock. This will let you 'rescue' many chips that have been set to the wrong type of oscillator, or change ones that are set from external oscillator (most Arduino bootloaders) to internal (such as the lilypad).

Parts

You will need…If you bought the kit from Adafruit, you'll have an extra few items such as a Piezo beeper, LEDs, buttons, etc. that you can use for the Standalone version of this project, just ignore them for now!

Assemble

First up, place the ZIF socket on the proto shield like so:
Solder all 28 pins for a solid connection!
Solder the following wires to the ZIF socket
  • Pin 1 to digital 10 - Blue Don't forget to bend the wire over underneath to connect to the ZIF socket pin when soldering!!!
  • Pin 7 to 5V - Red
  • Pin 8 to Ground - Black
  • Pin 9 to digital 9 - Gray
  • Pin 17 to digital 11 - Brown
  • Pin 18 to digital 12 - Orange
  • Pin 19 to digital 13 - Yellow
  • Pin 20 to +5V - Red
  • Pin 22 to Ground - Black
Follow the protoshield tutorial to solder in the Red LED into LED1 position, Green LED into LED2 position. Also solder in the two 1.0K resistors next to the LEDs. We'll use the LEDs as indicators. Then solder a wire from the LED2 breakout (white) to analog 0 and a wire from LED1 breakout (white) to digital 8.
Finally, you'll need to solder on the header to allow the shield to be placed on, break the 0.1" male header and place it into the Arduino sockets. Then place the shield above on top to solder it in place.

Load the Code

Time to load the sketch! Grab the code from our Github repository and paste it into a new sketch. Then upload it to the Arduino.
We have a report that this procedure does not work with Arduino 1.5.2. Use the latest mainstream Arduino release instead!
Plug the shield on top, lift the latch, pop in the chip and then lower the latch. Make sure the chip orientation is like so (so with the lever on the left side you can read the text):
With the USB cable still plugged in (and the same Serial port selected as before) Select Tools→Burn Bootloader→w/Arduino as ISP
On newer versions of the Arduino IDE, select Arduino as ISP from the Tools→Programmer menu, then select Burn Bootloader from the Tools menu.
The Green LED will be on during the programming, when its done you'll see this message and the LED will turn off.
Thats it! Don't forget, you can burn a few different kinds of bootloaders, such as Uno, Duemilanove, Lilypad so depending on your situation you may want to use one over the other.

Bonus! Using with AVRdude

You can use ArduinoISP from the command line very easily, with AVRdude which is the standard program used to program AVRs by running:
avrdude -c arduino -p atmega328 -P COMPORT -b 19200 -U flash:w:filetoburn.hex
Instead of atmega328 you can also program atmega8 atmega88 atmega48 atmega168, etc.