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Arduino, Hardware, Software

USB Configurable Arduino DDC Servo & Accessory Decoder – ArCoMoRa 2 – Configure an On Off Accessory

Now that we installed the Windows software (see previous video) and uploaded the MARDEC sketch to a DCCnext or to an Arduino, we can start to configure the 16 available ports to do what we want them to do.

The video shows an example of how to configure an on/off accessory on port 1 that switches via DCC address 8.

The next vodeo will show a double flashing light and control of a solenoid junction with a double one shot.

Read on below the video …



MARDEC has two modes of operation:

  • Configuration mode is where we enter commands to match output ports with DCC addresses and enter all the parameters needed with that output, like the accessory type or the servo min/max angles. The Arduino is connected to our PC or laptop via USB. When we enter the E (Exit) command , we switch to normal mode.
  • Normal operation mode is where the output ports are controlled via DCC addresses. USB connection is not needed in this mode. If we want to change the configuration we can reconnect USB and enter the C (Config) command to switch to config mode.


To configure a port as an accessory, follow these steps:

  1. If in Normal mode, type C to enter Config mode
  2. Type P and enter the port number we connected the accessory to
  3. Enter the DCC address we want this accessory to have
  4. Type 1 to make this port an Accessory
  5. Type M and enter the mode we want this port to have (see list below)
  6. Enter additional parameters if asked
  7. Type Enter to exit and store this port configuration
  8. Type P to configure another port, or …
  9. Type E to exit config mode and enter normal DCC operation mode

The following accessory modes are available:

  1. steady on / off, single port
  2. steady on / off, with an inverted buddy port
  3. one shot pulse, single port
  4. one shot pulse, with a buddy port, e.g. to switch solenoid junctions
  5. flash with separate on- and off times, single port
  6. flash, with an inverted buddy port
  7. PWM (analog) output, with a fade in and fade out
  8. flicker (uses PWM)
  9. random flash (seconds)
  10. random flash (milliseconds)


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About RudyB



One thought on “USB Configurable Arduino DDC Servo & Accessory Decoder – ArCoMoRa 2 – Configure an On Off Accessory

  1. Hello Rudy. Thanks for making these great tutorials. They are so informative and have helped me develop more of an understanding of basic electronics. I have a newbie question for you; can you explain to me how the DCC Next is wired up?
    The DCC signal from a controller (I use an ECOS) plugs into the blue connector bottom left corner, there is no positive or negative with these two wires, they can go in either slot, correct?
    The blue connector bottom right, can have 9 to16V AC or DC, this supplies the power to DCC Next via the “internal” jumper when in the normal mode, therefore it needs to be connected to a power source, correct?
    The blue connector top right 5V DC, is used when connecting servos, not needed if I want to test LEDs as you did in the video, correct?
    The green connector top left 5V DC for Input or Output. When and how do I use this?
    I connected the positive leg of a LED to a resistor and connected the other end of the resistor to port 5 of the DCC next. The negative leg of the LED goes to ground, but which ground?
    In your video the yellow wire goes from the LED to port 1, where does your black wire go to?
    Thanks again, and looking forward to your reply.


    Posted by Kai Grambart | December 18, 2020, 06:23

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