E15

RTB_E15

This E15 module implements a 12 channel WS2811 emulator with compatible bus timing to drive multiplex (charlieplexing) LEDs. The E15 may be cascaded with regular WS28xx chips. The number of LEDs attached is automatically detected (0-12). The LED voltage is fixed to 5V. The intended use is to drive Multiplex Signals on Model Railway layouts via the WS28xx bus.

Note: The E15 is nearly identical to the RTB_E13, but only allows fixed LED voltage.

<img src=supplemental/images/E15_main.jpg>

The decoder has the following features,

• Protocol
  • WS2811 compatible timing
• LED ports
  • 0..12 LEDs (auto detecting)
  • Charlieplexing (Multiplexing) output
  • 256 step PWM (300Hz)
  • LED voltage fixed to 5V (see also RTB_E13)
  • gamma correction (optional)
• firmware update via V24 debug interface

Hardware

My current PCB layout uses SMD footprints with 0.5mm pitch and 0603 parts. Reflow soldering is my recommendation, but with some experience handsoldering is also possible.

<img src=supplemental/images/E15_top_connect.jpg>

PCB

• 2-layer PCB, FR4, 1.6mm
• CPU: AVR64DA32
• BUS: WS28xx
• LED: Charlieplexing

Kicad

Schematic | Layout | BOM | Gerber

Firmware

Filename structure: { pcb }{ code }{ version }.hex

Example: E15F0001.hex

UPDI

The fuse settings as well as the P-code (E15Pxxxx.hex) has to be installed by using UPDI.

Debug Interface

Subsequent code updates can be done via the built-in serial debug interface.

Software

The LED intensity values for the individual LEDs need to be transmitted over the bus, with N being the number of configured LEDs.

Byte order:     {led_0} ... {led_N}

Images

<img src=supplemental/images/E15_samples.jpg width=260> <img src=supplemental/images/E15_usecase.jpg width=260>

This project is intended for hobby use only and is distributed in accordance with the Apache License 2.0 agreement.