Picture of Digispark DIY: The smallest USB Arduino
Digispark is an ATtiny85 based microcontroller development board come with USB interface. Coding is similar to Arduino, and it use the familiar Arduino IDE for development.

Digispark is copyrighted by Digistump LLC ( and the full license is here:

Support for the Arduino IDE 1.0+ (OSX/Win/Linux)
Power via USB or External Source - 5v or 7-35v (automatic selection)
On-board 500ma 5V Regulator
Built-in USB (and serial debugging)
6 I/O Pins (2 are used for USB only if your program actively communicates over USB, otherwise you can use all 6 even if you are programming via USB)
8k Flash Memory (about 6k after bootloader)
I2C and SPI (vis USI)
PWM on 3 pins (more possible with Software PWM)
ADC on 4 pins
Power LED and Test/Status LED (on Pin0)
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Step 1: Prerequisite

Picture of Prerequisite
AVRISP MKII In-System Programmer
ATTINY85 Microcontroller
2 x 3.6V zener diode
2 x 68 ohm resistor
1 x 1.5K resistor
USB cable (get from broken mouse or keyboard)
Some wires

Step 2: Burning bootloader to ATTINY85

Picture of Burning bootloader to ATTINY85
Like Arduino, Digispark require a bootloader to be running on ATTINY85. The bootloader will occupied 2KB flash memory.

Download bootloader
1. Download Micronucleus bootloader for ATTINY85
2. Extract the file ( to any folder
3. You can find the bootloader file at micronucleus-t85-master\firmware\releases folder
4. Use micronucleus-1.06.hex for the bootloader

Burning bootloader to ATTINY85
You must use the correct fuses bit for the bootloader

Extended: 0xFE
High: 0xDD
Low: 0xE1

Note: The above fuse bit will not enable reset as I/O, so you can have only 5 I/O instead of 6 I/O. I'm still try to figure out on how to set it to 6 I/O

I'm using AVRISP MKII In System Programmer and AVR Studio software for burning bootloader.

Step 3: Installing Digispark USB driver

Digispark use USB to communicate with computer, so your computer must install Digispark USB driver
1. Download Arduino for Digispark which come with USB driver
2. Extract the file (  to any folder
3. Execute DigisparkArduino-Win32\DigisparkWindowsDriver\InstallDriver.exe to start installing the USB driver

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bobricius1 year ago

Hi, I think that I have much smaller arduino than you

dan3008 bobricius11 months ago

Only just... I'm working on an even smaller one, if it works, It'll litterally fit inside a usb plug lol

how's that goin?

Apart from accidentally shorting my data wires on the first attempt (lucky it wasnt power...)its worked like a dream :)

uses SMD components. The difficult bit is pulling out the reamaming IO pins without shorting stuff...

Once I've got it working, I'll share the instructable :)

lzu bobricius10 months ago

I'm the Ardulink creator. Ardulink is a java open source library that can control and coordinate several Arduino boards.If you are interested in have PicoDuino supported by Ardulink, please contact me and send to me a board. I've already made a test with a Digispark.

MisterED.corp4 months ago


just wanted to thank you and throw in a pic of my attempt :)

the upper one is a usbTinyISP and the lower one the Digispark. I added a capacitor (10uF i think, but just used the next one laying around) to get usb-connection to work.

2014-10-12 17.33.28.jpg
smching (author) 7 months ago

Once you use Burn Bootloader, you can never program that chip again using an ISP programmer.,1051.0....

nvillalba smching7 months ago
Well! No problem! Thanks for warning me
nvillalba7 months ago
Can you explain this process whit arduino as ISP instead AVRISP mkII
Jaywalker19817 months ago

Would it work, If I connect P3 and P4 directly to USB+ and USB- on my micro USB connector?

What are the potential downsides of not using the zenor diode and the pull-up resistors for Level converting? Would my communication still work without those two? Could it fry my processor or the usb port on my host device?

smching (author)  Jaywalker19817 months ago

It wouldn't work without the Zener didoe & the pull-up resistor.

The USB power uses 5V, but the dataline (USB+ & USB-) uses only 3.6V for high, attempt to fed 5V from ATTiny85 to computer will cause the communication failed.

jemamena7 months ago

Has anyone tried to use an ATtiny84 instead with usb capabilities? It would be very helpful

smching (author)  jemamena7 months ago

Please check with Digispark Pro

jemamena smching7 months ago

What chip uses the Digispark Pro? I am actually more interested in making the ATtiny84 usb like the first Digispark

smching (author)  jemamena7 months ago
smching (author)  jemamena7 months ago

At first I thought it is ATtiny84 because it is discussing in the post related to ATTiny84:

By comparison the pin configuration and specification, I think it must be ATTiny167.

jmpm46191 year ago
Hello what can i do with this board perform?
smching (author)  jmpm46191 year ago

Digispark has 6 digital outputs, you can control LED, relays. It has 3 PWM outputs, you can control motor and fade the LED. It has 4 Analog inputs and can be connect to sensors.

Please refer to Digispark project forum for more details:,2.0.html?PHPSESSID=rmkknm79gl308nsk4tmhr4g9i6

DraakUSA smching8 months ago

Select the fuse RSTDISBL. That disables the reset function of the pin, and enables it as I/O. Note, you will need an HVSP to reset the fuse (or reprogram the AVR) after you do that.

PD, is there a way to communicate between the uC and the computer via the integrated USB?

You could try with my java library Ardulink. I've developed a connection for Digispark. It works also if some messages get lost.

smching (author)  Emiliano Valencia1 year ago
Communicate between Digispark & computer is not easy via USB. You can refer to Debugging with the Digispark

 would suggest to sending the data as keyboard keystrokes using the digispark keyboard emulation, it is very simple and easy. Otherwise you can use Softserial

zhaoyu35171 year ago


dan30081 year ago

Silly question. Whats the purpose of the 2 zener diodes?

I'm guessing its to stop a back flow from gnd to the data pins (or visa versa)?



smching (author)  dan30081 year ago

The host(computer) sends 0V(0.8V min.) for a low level and 3.3V(3.6V max.) for a high level.

The zener diode acts as the level convertor, the 3.6V zener diodes yield 3.3V in conjuction with an 1.5K resistor.

Ah i see. Thanks for that :) my electronics knowledge is a bit rusty lol

Ploopy1 year ago


Could you upload the fritzing file (.fzz)?

smching (author)  Ploopy1 year ago

dan30081 year ago

Just ordered myself 10 ATtiny84's to make these :D (well, one for a usb programmer, the rest for this) I cant wait to be able to develop USB devices and similar without the hefty pricetag of the arduino...

one set of fuses that will let the rest pin be used for io is
Low: 0xe1
High: 0x5d
Extended: 0xff

But I've not tested it yet, so cant guarantee it

letnic1 year ago
I get a "USB device not recognized" message. I try with 1,8k and 1,2k on D- and on D+ and all on work. My 2 zener are two 1n4729.
letnic letnic1 year ago
i miss spell, "all not work". I have no idea why it don't work
smching (author)  letnic1 year ago
Reverse the D+ and D- may cause "USB device not recognized" too.

I'm also facing "USB device not recognzed" when using an ordinary USB mouse cable,

Please use a good quality USB cable. The USB cable must be as short as possible.
smching (author)  letnic1 year ago
Thank you for sharing
koogar1 year ago
FUSEOPT_t85_DISABLERESET = -U lfuse:w:0xe1:m -U efuse:w:0xfe:m -U hfuse:w:0x5d:m

Use High fuse 5D this was taken from the digispark bootloader make file


ziggalo1 year ago
I plugged in my digispark and instead of the wizard popping up, I get a "USB device not recognized" message. Any ideas?
smching (author)  ziggalo1 year ago
Did you reverse the USB signals (D+ and D-)? Get the lowest wattage zener diodes you can.

Read here for more details.
Dr B1 year ago
Thank you smching. I did as you suggested. The sketches uploaded onto the Digispark ONLY on ONE computer running OSX 10.7. It still did not work on two other computers running OSX 10.4 and 10.6 (both of these were Intel Core Duo's running at 1.83 GHz). The one running OSX 10.6 gave a different error message than the one that I listed, above: Cannot run program "/Applications/DigisparkArduino-MacOSX-1.0.4-May19/DigisparkArduino-MacOSX-1.0.4-May19/": error=86, Bad CPU type in executable
at java.lang.ProcessBuilder.start(
at java.lang.Runtime.exec(
at java.lang.Runtime.exec(
Caused by: error=86, Bad CPU type in executable
at java.lang.UNIXProcess.forkAndExec(Native Method)
at java.lang.UNIXProcess.(
at java.lang.ProcessImpl.start(
at java.lang.ProcessBuilder.start(
... 10 more

Apparently the DIgispark IDE has a problem with the "Bad CPU type" (in two of the computers?).
Are these CPU chips too old to be compatible with the Digispark IDE?

FYI, the blog did not let me insert this message into the reply box because it asked for the two code words to be entered, but a brown box to do so did not appear under the reply box.
smching (author)  Dr B1 year ago
I only use MS Windows, I may not able to help you on this problem.
Anyway you can post your question to Disispark forum,4.0.html
Dr B1 year ago
Your website gives the most complete description and set of procedures for Digispark in one single location that I have yet seen. I am very new to Digispark and am confused by the bootloader part. I thought that Digispark came 1) with its own ATTiny85 hardwired on the board 2) pre-programmed, in that when inserted into USB port (Mac OSX 10.4) the LED flashed on and off @ 1Hz (if using the RGB LED shield, it flashes red, blue then green).
I cannot download either the Digispark "Start" or the "RGB" sketch because it will not compile (an therefore will not download). It gives the following error message:
dyld: unknown required load command 0x80000022
avr-gcc: Internal error: Trace/BCP trap program ld
Please assist me in correcting this situation. Thanks.
smching (author)  Dr B1 year ago
You must configure your Didispark software (Arduino IDE)
From the Tools menu select Board→Digispark (Tiny Core)

You need to your programmer to Digispark if you want to upload sketch
From the Tools menu select Programmer→Digispark

Refer to Digistump Wiki for more details:
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