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I'm trying to DIY about a dozen BlinkSticks (discontinued, Adafruit) pictured here

discontinued BlinkStick

I'm thinking to use a Digispark ATTINY85 to control a single RGB LED to show the status of some program running under Linux. Here is the proto board I have my eye on:

Digispark ATTINY85

I could either use a single individually addressable RGB LED with a built-in WS281X controller

RGB data LED

or a plain RGB LED with each color pin connected to a GPIO pin on the TINY85.

Plain RGB LED

This is my first Arduino project, so I'm not familiar with the best way to approach this project. I'm trying to keep the part count low as well so the serial data approach is appealing too. Has anyone done this before and can explain their setup?

Prior work I've found for the simple control approach:

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enter image description here

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    The blinkstick schematics are available: blinkstick.com/help/schematics
    – Craig
    Oct 8, 2018 at 17:35
  • A plain rgb led needs resistors and with the same resistors one color is brighter than an other color. So you have to tune the resistors or the pwm in the code. A rgb led with built-in controller is easier to get a certain color, and the controller has often more than 8 bits so very dim values are no problem. However, you need a library which uses flash and ram which is very limited for a attiny85. The best option is a atmega328p with a rgb led with built-in controller. Everything else is looking for trouble.
    – Jot
    Oct 8, 2018 at 17:42

1 Answer 1

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The newest blinkstick uses an addressable led, while the Adafruit kit appears to use a regular 4 pin RGB led. These are easier to get.

The digispark and the blinkstick are almost identical, but they use different pins for the USB connection. So to use the firmware for the blinkstick on the digispark, you need to change the pin numbers in usbconfig.h

#define USB_CFG_DMINUS_BIT      3
#define USB_CFG_DPLUS_BIT       2

PS. the pin numbers in usbconfig.h don't seem to match the schematic, so I'm not sure what's going on

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  • This is a good observation. Thanks for taking the time. I'll assemble the project with the ATTINY85 board I've found and the WS2812 LED plus the capacitor, then adjust the firmware as you indicated and report back how it works. Thanks again.
    – Drakes
    Oct 8, 2018 at 21:38
  • I don't think you need the capacitor. Best of luck.
    – Gerben
    Oct 9, 2018 at 12:18

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