RTB_D98

This is a opendcc forum project

The hard and software is based on the D16 motor decoder. It implements a double-sided NEM-651 function decoder for use with DCC infrastructure. The hardware provides

• 10 auxiliary output ports
• up to 32 WS281x neo pixels

Note: this repo is currently under construction and will be completed soon. (Feb 20, 2026)

See also

• RTB_D16 - NEM651

User Guides

• User Guide - DE
• User Guide - EN

The decoder has the following features,

• NEM-651 connector
• DCC
  • DCC-A automatic logon
  • DCC-R protocol extension
  • Service Mode Programming
• Railcom
  • Channel 1/2
  • POM, xPOM, Long_1
  • DYN: QoS, Track-voltage, AUX-current, Temp, East/West
• double sided
• Dimension: 13 x 9 mm
• 5-20V track voltage
• heartbeat LED
• adjustable max AUX current (default 500mA)
• over temp protection
• Function output
  • LV/LR/AUX1/AUX2 open drain
  • AUX3/AUX4/AUX5/AUX6/AUX7/AUX8 logic level (5V)
  • LV/LR/AUX1/AUX2/AUX3/AUX4 (dimmable, 1.4kHz)
  • WS281x: up to 32 WS28xx neo pixels
• optional external buffer capacitor (max. 1500uF)
• <10mA idle power consumption
• Firmware update over main tracks via DCC-R protocol

Hardware

The current PCB layout uses SMD footprints with 0.5mm pitch and mainly 0402 parts. Reflow soldering is recommended, handsoldering nearly impossible.

PCB

• 6-layer PCB, FR4, 13 x 9 x 0.8mm (double sided)
• CPU: AVR64DA32
• Connector: NEM-651 (or solder)

Kicad

Schematic | Layout | Gerber

Dependency

🟡 Requires my Kicad project library RTB_SamacSys in the same directory tree.

Firmware

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

Example: D98F0001.hex

	Description
pcb	Name of matching hardware (D98)
code	Type of code contained (R=rom, B=bootloader, F=flash, U=bld update, P=UPDI factory code)
version	Release version (####)

Firmware files

Images

top	bottom

YouTube

Some YouTubes to see the D98 decoder in action.

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