Use a $1 ATTiny to drive addressable RGB LEDs

Arduinos are wonderful and easy to work with, but there are some projects where you need a microcontroller, or want to add some interactivity but don't really want to dedicate a $20-30 board!

At a little over $1/each (less in bulk) the ATTiny85 is a great chip for the job: it has 6 I/O pins and is capable of 16Mhz with minimal external components, is enough to work with many sensors, even drive popular addressable LEDs like Adafruit's NeoPixels, WS2811 strips.

The setup process is a little technical, but not too scary I promise, and you can use the familiar Arduino programming environment.

What you'll need:

* An ATTiny (this tutorial uses the ATTiny85-20PU)
* a USB ISP AVR Programmer (My tutorial uses this one)
* a breadboard
* some jumpers or wires (color coded wires are really helpful)
* a computer with the latest Arduino software installed (if you don't already have it, download here)
* a 5V wall wart (Old cell phone power suppliers work wonderfully, double check them for a 5V output. If you need one, these are plentiful at thrift shops!)
* 5V Addressable LEDs (this tutorial assumes use of 3-wire WS2811/WS2812)

Very helpful:

* .10 uF capacitor
* 1 low value resistor (ex 47, 100, 220 Ohm)
* A plain 1-color LED for testing

If you're looking for addressable RGB LEDs try Adafruit's Neopixel line or WS2811. They come in strips, pixels, segments, modules of many varieties. Working with 5V (as opposed to 12V) will be easier for this tutorial, so that's what I recommend!

You can try this sample code if you want to use your ATTiny with lights and a push button or touch sensor!
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stmarco4 months ago

Thanks for this instructable, i was trying it on my own but my ATtiny was not working at the correct speed, thanks to the flashing of the bootloader everything works now :)

danasf (author)  stmarco4 months ago

Wonderful to hear!

nomuse6 months ago

Did you have to burn fuses to set the ATtiny85 at 16MHz? I thought it came out of the box at 8MHz.

danasf (author)  nomuse6 months ago

I believe the fuses are set at 1MHz by default but I could be wrong. You can use the tiny at either 8MHz or 16MHz to drive the pixels, when I published this the library was only compatible at 16.

nomuse danasf6 months ago
Thanks -- this helped a lot.

I updated my ATtiny defs file with the latest version, then ran "Burn Bootloader" from the Arduino IDE whilst connected to my "naked" ATtiny85 via the same Adafruit ISP you are using.

Success, appears to be running at 8kHz, and I have a whopping 8K of program space in order to control my 4 neopixels.
mexx047 months ago

I can't compile the sketch for ATTiny85, maybe Adafruit has change something.

I have errors like:

C:\arduino-1.0.5\libraries\Adafruit_NeoPixel/Adafruit_NeoPixel.h:47: error: expected `)' before 'n'

danasf (author)  mexx047 months ago

Is your ATTiny set at 8Mhz or 16Mhz? Try the other clock value if you haven't already. Set the value, burn bootloader, upload?

If that doesn't fix it, this old fork of NeoPixel library was designed for (Tiny based) Digispark, what I used before support was added to the main branch.

mexx04 danasf7 months ago

It did not matter what frequency I had set, it did not even want compile.
Now I can compile the Blink and strandtest.ino example, but get the following error in the attiny_pixel_switch.ino:
arduino-1.0.5/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/lib/avr25/crttn85.o In function `__vector_default ':
(. vectors +0 x8): relocation truncated to fit: R_AVR_13_PCREL against symbol `__vector_4 'defined in section text.__vector_4 in core.a (

arduino-1.0.5/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/lib/avr25/crttn85.o:(.init9+0x0): relocation truncated to fit: R_AVR_13_PCREL against symbol `main 'defined in section text.main in core.a (main.cpp.o).

Perhaps you could create me one. BIN file for 50 LEDs? Thank you.

danasf (author)  mexx047 months ago

Oh this is the dreaded attiny and sketch >4k problem! See this forum post, for files/solutions to fix it:

And here's a .hex for 50 LEDs

mexx04 danasf7 months ago

Thank you for all!

The patch solved my compiling problem.

MiketheChap10 months ago
I've been working on this for awhile. The thing that throws me here is this statement under the Step 4, the Blink Test: "Connect a simple LED, the positive end to digital pin 4 on the ATTiny and the negative to ground." From the chip pin description picture, it looks like Pin 4 IS the Ground. 
It's just me being an idiot, I know, but could you clarify?
danasf (author)  MiketheChap10 months ago
Hey Mike, sorry, you're right, that is a little confusing!

Digital Pin 4 is Pin 3 on the IC (Ground is pin 4 of the IC).
MiketheChap danasf10 months ago
Thanks for the update!
When driving large strips only share ground and data having power crossed can make more noise and make the attiny pll even more unstable then it is. Using a real clock and not the pll can increase the number of lights you can drive by a little bit thanks to a more stable signal.
How many LEDs do you think I can stably drive without adding a quartz crystal? I currently have a NeoPixel 64 LED grid being controlled by an Uno. I would like to shrink the project down using an ATtiny.