I sell on Tindie

...Some kits are also available at ebay

tinyUSBboard in SMT

tinyUSBboard - the DIY AVR (VUSB) board

Arduino compatible without extra programmer and/or FTDI chip (USB<->serial) needed! Plus exchangeable bootloader!
Usable to construct your own (V-)USB devices like keyboards, mouses or your own protocols.

New! bootloaders version v0.97.1 available !

New! default "selftest" firmwares available, overdue a looong time!

New! exclusive GitHub repository for tinyUSBboard online !

New! Section about constructing the rev.4 SMT board !

New! Section about the bootloader with API !

New! related Contents and new Arduino Boarddescriptions for tinyUSBboard !

News! Finally tinyUSBboard revision 4 is available in SMT: Lots of stuff coming up soon! (survey)

News! Programm AVR firmware in C or ASM without installing any software or driver: avrstick - tinyUSBboards successor !

Do you have some ideas for further example firmwares - or even completed ones already? Please send them to me.


VISITOR SURVEY: Please answer the tinyUSBboard rev.4 poll

Introduction - What is tinyUSBboard?

TinyUSBboard is an Arduino compatible, minimalistic and cheap AVR microprocessor board with USB interface and simple "do it yourself" capability.
It utilizes directly features of USB without FTDI chip and/or any USB to serial converter. It can be programmed via assembler, C, Arduino or of course BASCOM.
All its components you need to construct it are universal and available nearly everywhere - no special PCB needed.
It is well suited for beginners to learn AVR microcontroller programming and/or it can be used on solderless breadboards very simple to do various projects.
For example using some firmware provided on this site turns it into a programming hardware for blank AVR microcontrollers, which can be used to produce further tinyUSBboards for family members, friends or collegues...

While normal handling with microcontrolling units (MCUs) needs additional equipment, tinyUSBboard only needs a Mac-, Windows- or Linux computer with a single free USB socket.

The board (see photo and layout) in form of a regular stick (approx. 2.5cm x 8.0cm) uses an ATmega8-16PU MCU, clocked at 16MHz.
This IC allows up to 8kib of programmed code within its flash-memory.
It also has additional 512byte persistent electronical eraseable memory (EEPROM) and 1kib volatile memory RAM.
(For further features see its datasheet in the datasheet-section).

Of course it is possible to use tinyUSBboard with other microcontrollers (for example ATmega328), too. For details contact me.

Three of the MCUs pins (PIN2, PIN12 and PIN13) are actually used for the USB interface.
This feature and using the latest, preflashed bootloader "USBaspLoader" (https://github.com/baerwolf/USBaspLoader) allows convenient and fast programming via USB, again and again:
Just press (keep pressed) the program-button and reset (or powerup) the stick.
The bootloader, emulating an usbasp-programming hardware, will take over and allows (re)programming the MCU.
(Once started, of course, the prog-button can be released. Any repeated press (or "reset") then will exit the bootloader.)

Furthermore, there are five LEDs on the board. One LED indicates the power supply via USB.
The other four (red) LEDs are connected to and can be controlled via the IO of the microcontroller (PB0, PB1, PD3 and PD5).
If in any circumstances only the direct contacts of the controller are required, LEDs can be disconnected permanently.

The bootloader occupies 2 of the 8 kib of flash memory.

go to: the top of this page

Advantages against other AVR VUSB boards

Althought there are lots of AVR boards available, tinyUSBboard has because of its special design and the complete revised sourcecode of USBaspLoader some unique advantages against other AVR VUSB boards. A list with the most outstanding ones is collected here.

Hardware advantages:

Software advantages:

In case you have some comments to this section (more advantages? disadvantages?) please share them with me.

go to: the top of this page

Pictures, schematics and layouts:

First revision






go to: the top of this page

Revision 2:






go to: the top of this page

Revision 3:

Revision 3 will swap connections of PD6 and PD7 in order to enable even more functions of the MCU.


If you experiencing instabilities during operation (ATmega8A, ATmega328p?) put some capacitor with 0.1uF or more somewhere near the microcontroller between Vcc and GND. (For example between PIN 7 and PIN 8)













(Using as USBasp programmer: White cable is optional 4MHz rectangular clock.)

go to: the top of this page

Revision 4 in SMT:

Revision 4 is 100% compatible to its predecessor revision 3. You CAN use revision 3 firm-/software.
However, the schematic has been pimped (even they are mostly identical).
The new schematic also is available in PDF or EAGLE (tinyusbboard.sch, tinyusbboard.brd) formats.


















go to: the top of this page

List of components

Rev4 surface-mounting technology (SMT) components

TinyUSBboard now also is available on an even smaller PCB.
It looks prettier, is faster to build and it is better for massproduction.
It is also cheaper, more robust and might be useful in other (kickstarter?-)projects as the center logic board.
If you are interested, please contact me...

The components are listed in blocks of recommended construction order. Total value should be less than $5.



Per board you basically will need:

Rev4 surface-mounting technology (SMT) soldering manual

At the moment there is no official manual for soldering the board. (It is not ready, yet.)
However there is already a lot of stuff from betatesters and fans in the net.
During construction this might help you:

go to: the top of this page

Rev3 through-hole technology (THT) component

In case you need some parts to build your own tinyUSBboard or you are unsure about sth., contact me...
The components are listed in blocks of recommended construction order. Total value should be less than $6.



If you want to build your own board(s) you may want to check out my construction-part kits available on ebay.
You also can contact me to trade a construction kit for bitcoins.
Usually the price for a Revision 3 kit will be around 0.07BTC including shipment within Germany.

Per board you basically will need:

For soldering you may also need about 0.75m to 0.85m of (1mm in diameter) Sn60Pb40 solder wire, which is however not seen as a component here.
If you experiencing instabilities during operation (ATmega8A, ATmega328p?) put some capacitor with 0.1uF or more somewhere near the microcontroller between Vcc and GND. (For example between PIN 7 and PIN 8)

go to: the top of this page

Useful addons for tinyUSBboard

Even tinyUSBboard can be used standalone with just one USB-capable computer necessary, you might want to extend playing with it.
Some useful first-step hardware addons are collected here:

For further suggestion please contact me.

go to: the top of this page

Chicken or the egg (How to get the bootloader into the AVR)

Some people contacted and pointed out to me, that there is always the same "chicken or egg" issue with these kind of DIY boards.

Since real beginners don't have any equipment (i.e. a programming hardware) nor an already working board (which they could use as a programming hardware), how can they program the microcontroller to build their own board for the first time?

In this section I would like to present and collect ideas to handle this issue. Please contact me me, if you want to contribute to this list or just have remarks to it.

  1. If you already have for example some working tinyUSBboard, you can program and use it as an USBasp programming hardware

  2. The most easiest way to get your first controller programmed: Ask friends, go to local university or order a preprogrammed controller. For this purpose I try to offer (see here) an ebay auction. However this option may be not practical, esp. the last one outside of Germany.

  3. Even if there is not any equipment available. One thing nearly always is at the users disposal: Computers often (esp. the old ones) are equipped with some serial or parallel interface. ("COM" or "LPT" as windows users like to call them.)
    In such cases you could build and use a PONYPROG (
    But be careful the circuit may not be safe for your computer - it better should be an old one! And you really should just use it in rare cases. (For example just for building your tinyUSB board)

    Since USB emulators for such serial/parallel interfaces mostly do not work with ponyprog and you may only have a new or mobile computer, this option may also be unsatisfying.

  4. USB HUB ISP - Use an USB hub for ISProgramming by switching ports on and off.

  5. Sound Programmer (only GERMAN, also 1 and 2)
    I know there are bootloaders out there, which allow the AVR being programmed with sounds (from ADC input pin).
    THIS IS NOT SUCH A THING! (Because needing an installed bootloader wouldn't solve the chicken/egg problem.)
    This Trick lets your soundcard generate MOSI (right channel) and CLOCK (left channel) signals for true ISP programming.

  6. Also with a computer and maybe some simple transistors (and photo resistors or photo transistors) available, you could interface the computers keyboard LEDs (num-, caps-, and scroll-lock) as SCK, MOSI and RESET lines (to you AVR microcontroller). Even if your default keyboard has no LEDs or simply is too expensive to be "interfaced", you simply can plugin any further keyboard suitable for this purpose. (Since most operating systems broadcast the LED state to every keyboard connected.)
    You now just need to implement a program doing the ISP via flashing the keyboards LEDs. It may be slow - but it should do the job.

  7. Hardcore DIY

go to: the top of this page

Some interesting material

go to: the top of this page

Related projects

go to: the top of this page


go to: the top of this page

The bootloader

Althought tinyUSBboard has a variaty of different (and exchangeable) bootloaders, its default one is USBaspLoader.

In normal mode the bootloader simply starts up the firmware, the user programmed into the AVR last time using the program-mode.

Additionally the bootloader implements some API, which can be used for example to write-access the flash from inside your own firmware.
This also makes it possible to provide migration- and update-firmwares (an application-section-firmware which exchanges the bootloader during its own execution).
With migration firmwares the bootloader can be either exchanged with some complete other bootloader:
For example switch out the default USBaspLoader bootloader with some other ones.
Or the bootloader can be exchanged with some other version of itself - this way the user always can maintain recent patchlevel and feature set.

By pressing the PROG button (effectively putting PD6 to GND) during a reset or power-up, the program-mode will be entered:
There the bootloader impersonates an USBasp programmer and makes all the different memories and data of the AVR available for your programming tool.


Bootloaders used on tinyUSBboard implement specific code, allowing normal firmwares to utilize some of the bootloaders functionality.

This way you can enable your firmware to do things (like writing to the flash), which normally is impossible due to hardware restriction.
The API also enables you to interact with the bootloader via software.

Get the tinyUSBboard API from GitHub

go to: the top of this page


go to: the top of this page

USBaspLoader updates specifically for tinyUSBboard

In normal mode of operation the bootloader (USBaspLoader) protects itself from being overwritten due normal uploads.
In order to update your tinyUSBboard's bootloader you first have to upload a special "updater"-firmware.
This procedure is exactly the same as uploading a normal firmware.

After the "updater" is uploaded, the bootloader has to be exitted to start the just programmed firmware. (Replug or reset the board.)
When the "updater" takes over control (LED on PD5 flashes), it first checks the current installed bootloader with the one contained within the "updater".
If both are identical, no writing is performed and it stops working by signalling "operation complete" (LED on PB0 flashes, too).
If there are differences it starts overwriting the existing bootloader with the new one. WARNING: In this phase the board should not be disconnected from power until it signalls "success" by flashing the LED on PB0.(LED on PB1 only flashes when update was done).

The procedure can be repeated some times (since the updater checks before write), until the updater haven't done any change anymore and it only signalls completition with LEDs PB0 and PD5. (PB1 will not flash).
After this it is save to upload (and overwrite the "updater" with) new firmwares by the user...

In order to protect the bootloader on tinyUSBboard from wrong "updates", which do not meet the necessary conditions (PIN layout, clock ...etc...), since version v0.9 it uses a magic value. This magic will prevent the old bootloader from being replaced by some inappropriate one (which results in loosing access to the board).

Revision 3 and newer

ATmega328P version

Revision 2 and older

go to: the top of this page

Upgrade old boards to revision 3 (experimental)

This section describes how you can patch your old tinyUSBboard into a revision three board in only a few steps.
Roughly spoken there are four major milestones to do:

Soldering is required for the hardware part (step three). Of course the board needs to be switched off during the process.

Basically you first unsolder the cables end at PD7 for the PROGRAM button.
Then you disconnect the corresponding pin header from microcontrollers PIN (PD7). (This ensures an important safety measure: The future USB (D-) line must not be accessable on the outside (i.e. on a breadboard)).
Now also disconnect PIN PD6 from its inner USB D- connection rail. Connect the MCUs PIN PD6 with its corresponding pin header.

Extend the inner USB D- rail and connect it to MCUs PD7. (Its pin header stays disconnected!)
Solder the cable to MCUs PD6, which already should be connected to its pin header.

Done! Now you need to continue with step four...

Finally you may want to install a revision 3 update to get recent bootloader.

go to: the top of this page

Other controllers for revision 3 (and newer)

Revision 3 will swap connections of PD6 and PD7 in order to enable even more functions of the MCU.
(It is possible to use the internal analogous comperator module)
If you experiencing instabilities during operation (ATmega8A, ATmega328p?) put some capacitor with 0.1uF or more somewhere near the microcontroller between Vcc and GND. (For example between PIN 7 and PIN 8)


Other default- and bootloader firmwares only are provided for revision 3.
Most of them are still inofficial and need further testing.
If not noted otherwise, example binaries/hexfiles are always compiled for ATmega8.

An arduino hardware description also is available for ATmega8 and ATmega328P only.

  1. USBaspLoader version v0.97.1      (For Updates: Please ensure how updating works!!)

  2. !! BUG !! USBaspLoader version v0.97

  3. !! BUG !! USBaspLoader version v0.96.2 or older

go to: the top of this page

Programming in C (or assembler)

In order to program appropriate firmwares for tinyUSBboard, you can choose out of many programming languages.
If you want to use famous C language you might want to do this via open source avr-libc and its chain of tools.

Since the toolchain just generates the binary-data, you still need a piece of software to bring it into the MCU.
Because there are some major differences between the available platforms, the following subsections will explain some tools doing the job...

If you want to have some empty skeleton to start with your firmware, you might want to look at my avrskeleton at github.
(Just define environment variable "AVR8TOOLCHAINBINDIR" with the PATH to your toolchain binaries and the Makefile will do everything else.)

In case you want to see/experiment or just play with AVR assembler you can try out this.


Atmel offers directly two precompiled avr-libc toolchain versions for linux.
One LZMA recompressed version for 32bit systems is available here, and another for 64bit here.
At your raspberry pi (using raspbian), you can use this build.

For flashing the data into tinyUSBboard you can use AVRDUDE.
(avrdude -c usbasp -p atmega8 -D -U flash:w:main.hex)


For using tinyUSBboard with Windows, you first have to install some usb-drivers.

A good programming software I recommend as graphical replacement for avrdude is KhazamaAVRProgrammer (link).

Even there is also an avr-libc port (avr8-gnu-toolchain-installer- available for Windows, you might try out Atmels AVR Studio

Since the new toolchain avr8-gnu-toolchain-installer- is without an installer and thus harder to setup/use, you might want to use older avr-toolchain-installer- available from the mirrors instead.


Using tinyUSBboard with Mac is completly untested. For reports I would be very thankful.

Under Mac you can try (use?) CrossPack for AVR Development.
It runs on Mac OS X 10.6 or higher and promises to be similar to AVR Studio on Windows.

go to: the top of this page

Programming in Arduino

"Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments."

How you can download the appropriate arduino-ide version for you will be explained in the following subsections.
Before you can start using arduino-ide after downloading and extracting it, you have to extend the list of know boards to arduino.

Therefore all you need to do is to extract this zip-file (or this tgz) into your arduino directory.
This is the new and recommended way to use tinyUSBboard within arduino IDE.
Please only use stable mainline Arduino IDE version 1.x.. (Download URLs are below.)
Borddescriptions in Arduino 1.5 aren't final and only available as a draft at the moment.

The old way was to copy this text below into "/arduino-####/hardware/arduino/boards.txt".
(Or to use this patch.)

Please also note the different PIN-names (compared to the datasheet) in arduino. (See more)


Arduino for Windows

Here you can download the arduino-ide for windows.

Arduino for Linux

Arduino for Linux is available in two versions: One for 32bit systems, and another for recent 64bit technology.

Arduino for Mac

Arduino for Mac OS X

go to: the top of this page


For the moment all arduino and avr-libc toolchain files are mirrored within an GMX mediacenter. HERE

go to: the top of this page


In case you have any problems/trouble and/or need some help,
in case you have remarks or you want to participate tinyUSBboard-project,
in case you need some parts to build your own tinyUSBboard,
you can contact Stephan Bärwolf via:

If you want to use PGP, my key-id is 0xFB9B12DB.
The corresponding fingerprint must be: 2252 B41E 12DF 41AD 476F 7F36 084A 0911 FB9B 12DB

go to: the top of this page

last change: 2015-01-02T23:00Z