Desklight panel

ATTiny10-powered WS2812 desklight

Controller firmware and hardware for a very simple desklight that has a button and a digital encoder for color/brightness selection.

Controls a strip of WS2812 RGB LEDs which could e.g. be mounted at the bottom edge of your desktop monitor facing down towards the desk surface.

(Above: bottom side of v1.0 PCB)

Authors

David R. Piegdon dgit@piegdon.de

License

All files in this repository are released unter the GNU General Public License Version 3 or later. This includes the schematic, the routed PCB and the firmware as well as the documentation and accompanying materials. See the file COPYING for more information.

Device interface

The rotary encoder has a button and can be rotated in both directions. The button cycles through different modes. In each mode you change a different variable by rotating the encoder:

• Mode 1: change brightness

• Mode 2: change color

• Mode 3: change number of enabled LEDs

• Mode 4: change starting position of enabled LEDs

Pressing the button for more than half a second resets all values to their defaults.

Firmware

You probably have to use a recent AVR-GCC Version for compilation. Version 5.4.0 is good, 7.3.0 yields even better results. As the ATTiny10 is very space-constrained, older gcc versions may not optimize well enough to meet the space-constrains with the current feature set.

If you want to change the number of lights in the firmware, please do so in ws2812.h. If you know what you are doing, you can also change the assignment to light_count in the firmware files (in ws2812_init(), calca_init(), if you don't want to recompile.)

Note that with the current master branch firmware you can use up to 126 LEDs. The actual constraint is something like lightcount <= max_value(int8_t)-1.

Firmware Changelog

v1.0

Supports four modes (brightness/color/enable-count/start-pos), should support 63 LEDs. Required GCC 7.3.0 or similar to fit size-constraints.

v1.1

Improved binary size. Now supports building with GCC 5.4.0.

v1.2

Support up to 126 LEDs.

v1.3

Fixed rotary dial directions to be consistent across modes.

v1.4

Fixed WS2812 timings to properly work with all LEDs. Allow LIGHT_COUNT to be overriden via CXXFLAGS.

master

(no more changes)

Hardware

You can find a Kicad-based schematic in the hardware directory.

The firmware is written for an Atmel ATTiny10. The latest version does not use the ADC anymore, so an ATTiny9 should do fine, too.

Connect a 5V 1500mA (or better 2000mA) power supply for a strip with 34 LEDs.

Hardware Errata

v1.0

Version 1.0 of hardware is fully functional and works perfectly fine. However, a few changes might be useful when doing another revision:

• Schematic: Remove comment on questionable 1K resistor value. 1K resistors between uC and encoder are ok. Comment in schematic was already removed shortly after tag v1.0, as already can be seen in released PDF schematic of v1.0.

• Schematic/BOM: Create a BOM. Well, maybe just specify the kind of rotary encoder. (Look for EC11 digital encoder on your favourite cheap chinese parts supplier)

• PCB: Increase drill size for power lines on P2 and P3, so power cables can be soldered directly to PCB easily.

• PCB: Mark RESET pin of TPI so it can be found easily when re-flashing a uC.

• PCB: Mark TPI interface as "TPI".