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Model Railroad Control Systems

cpNode Version 2.0


cpNode Version 2.0

0.20 LBS
Calculated at checkout

Product Description


cpNode and I/O expander (IOX) boards have been updated to version 2.0. Based on customer feedback, and our design and installation experience, the changes were made to provide more efficient and flexible physical layout of some components.


 Rev 2.0 boards are 100% backward compatible with current versions. No software changes are needed.

Version 2 brings the following improvements to the proven cpNode design:

  • Board size 2.7" x 3.9", same as the IOX32 and ODX4
  • CMRInet interface connection has been made consistent with five position pads (R+, R-,T+,T-,SHLD).for 3.5mm screw terminals, .156" Molex male pins, and .100" (2.54 mm) Molex KK male pins.
  • Input/Output pads moved .2" back from edge for better DIN rail clearance. The I/O option pad area accepts standard DIP component headers with .3" and .4" pad spacing.
  • Gnd/LED Com pads aligned to .1" (2.54 mm) for a screw terminal block or male header pins
  • I2C interface connector moved to I/O side of board
  • Solder jumper pad (SM ENA) to connect port A0 to RSMC


What does a cpNode do?

cpNodes provide input and output (I/O) ports which connect to LEDs for signals, push buttons, turnout motors, block detectors, and other devices to a central computer for controlling model railroads.  cpNodes may also be used as standalone controllers for staging, crossings and interlocking plants.

  • You must provide a Bread Board Leonardo (BB-Leo) processor, available from Modern Device, use coupon code "cpnode"  (DO NOT order the header kit as headers for the BB-Leo are included in all assembled cpNode configurations.)
A cpNode has:
  • 16 I/O lines with solder pads for LED limiting resistors
  • Screw terminal blocks or headers to connect external devices - see configurations below
  • CMRInet RS-422/485 Network Interface.  CMRInet is now NMRA Layout Control Specification S9-10
  • I2C interface for adding Input/Output Expander (IOX) boards for more i/o ports
  • Optional Stall motor controller - order the "RSMC" option
  • Everything needed to control one end of a CTC siding, just add signals and detectors
  • Female headers to receive a BB-Leo (Arduino) processor available from Modern Device, use coupon code "cpnode"
  • I/O is configured in 8 bit groups, providing up to 144 lines when fully expanded with IOX16s and/or IOX32s
  • Use cpNodes as small, economical, CMRI nodes as is or customize the code to support applications requiring local intelligence
  • BB-Leo uses the Atmel Atmega32u4 processor chip, see the data sheet for electrical characteristics
  • Standard "Sketch" (Arduino program) is compatible with JMRI or traditional BASIC/Visual Basic development tools


  • The default configuration (AT) has screw terminals installed for the CMRInet and 0.100 screw terminals for the i/o, most users will want this option
  • The Remote Stall Motor Control (RS) option has screw terminals installed for the CMRInet and 0.100 screw terminals for the i/o and circuitry to drive a stall motor
  • The Male Header (MH) option has screw terminals installed for the CMRInet and 0.100 male headers installed for i/o.  The user is responsible for providing matching 8 pin x 0.100 cables
  • The No Header (NH) option has screw terminals installed for the CMRInet and no i/o connectors so the user can install his 0.100 connectors of choice contact us for a quote if you want custom assembly with your favorite connector)
  • BB-Leo (LE) Configuration is the default (AT) configuration with a BB-Leo installed, this is ideal for customers desiring a single source , especially international customers wanting to consolidate shipping

If you need a configuration which isn't listed, please contact us and we will be happy to quote you on a custom configuration


We offer the BB-Leo with headers as an option for those who want to combine shipping or have a single source solution

Use the Bare Board Option if you want to assemble your own or contact us for a custom quote for an Assembled and Tested unit using your favorite connector.



Configuration Instructions


Technical Guide

cpNode Schematic

cpNode Instructions

cpNode Build BOM

cpNode Kernel sketch for Arduino

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