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The Layout Control Node

The Layout Control Node (LCN) is the the basic hardware assembly containing the LCOS firmware. The firmware is currently available for the ATMEL 328P microprocessor. Additional microprocessor types will be supported in the future.

LCOS firmware comes in two primary variants: the MASTER Node and the CLIENT Node. Both variants use the same hardware platform; a label on the bottom of the board identifies the loaded firmware.

The Hardware

Gen 1 Layout Control Node.


The mounting holes are 3mm diameter. The best way to mount an LCN is to use M3 Nylon Standoffs with a screw post. We fasten the standoffs to the board with matching nuts, then glue the other end of the standoffs to the underside of the layout. Use CA to attach standoffs to wood or metal; foam safe adhesive for attaching to foam. When the glue is set, you can easily remove and replace the board if necessary.

In general, once installed you rarely need physical access to a client node. Nevertheless, you should locate an LCN so that you have reasonable access to it when necessary. After layout construction, the primary reason to physically access a Client Node is to apply a firmware update.

The MASTER node should be attached to your main control panel. Its USB port must be easily accessible so that you can run the Configurator. If necessary, leave a USB cable attached to the MASTER so that you can connect at will.

Powering Your LCN

General power requirements are discussed in the LCOS Layout Planning Guide.

An LCN with no peripherals attached can be powered by USB. This is useful for initially setting the radio channel and node ID on your LCNs. Thereafter, power your boards as discussed in the guide.

If possible, connect 12 volt DC to the LCN via the barrel jack; we recommend 18 ga pigtails for connecting your LCNs to the Layout Control Bus. Your can also use barrel jack adapters. Alternatively, attach wires from your LCB to the VIN and GND terminals on on the Node assembly.

Production LCNs are able to handle and share with peripherals up to 2 amps @12 volts. By using the barrel jack for power feed, you leave the VIN and GND terminals available for power sharing with other devices.

However, the +5v terminal has limited power handling capabilities. Accordingly DNIN8 and DNOU8 duinoNodes must be powered by the LCB and should not draw on +5v LCN power. PCA9685 drivers can take logic power from the +5v terminal safely.

On-Board Status LEDS

All production LCN boards have the following 4 status LEDS:

4 Standard LCN Status Indicators
  • LED1 — VIN power LED; indicates board is receiving external power through either the barrel jack or the VIN terminal.
  • LED2 — Red Status LED. On during boot and off when running normally. Works with LED3 to indicate specific error conditions. See below.
  • LED3 — Green Status LED. Off during boot, then on when running normally. Works with LED2 to indicate specific error conditions. See below.
  • LED4 — Radio Transmit LED. Comes on during radio transmit.

Adding Optional External Status LEDS

You can extend the LED2/LED3 combination to your fascia by attaching a pair of LEDS as shown below.

These LEDS convey basic information about the state of a Node, including its boot state, radio availability, and its current operation mode. Use two LEDS – one green and one red. We use a special wiring arrangement to allow one port to control both LEDS.

The two LEDS use the +5 volt pin and a ground pin on the LCN, with the middle wire connected to port A3:

For lack of better terminology, we call this a HIGH/LOW switching circuit. When A3 is LOW, the Red LED on the left lights up. When A3 is HIGH, the Green LED on the right lights up. When A3 is INACTIVE (no electrical connection) both LEDS light up at reduced brightness.

Place the LEDS at a convenient place on your fascia. If something isn’t functioning, the first step is to check the LEDS to quickly determine the state of the Node in question.

In this example, the LEDS and resistors are soldered to a 3-wire cable (servo extension cable), with shrink tubing protecting bare leads from shorts. These are standard 3mm clear lens LEDS, red on right and green on left. The red wire attaches to the +5v terminal on the LCN, and the black attaches to LCN ground. The yellow wire goes to terminal A3 on the LCN.

The LED states are as follows:

  • Both LEDS lit: LCOS is not running. During brief pre-boot, both LEDS will light but should shift to the boot state within a second or two. If both stay lit, then either the processor does not have the LCOS firmware loaded, OR the processor has failed.
  • Red LED on steady: LCOS is booting.
  • Red and Green LEDS flashing alternately at a moderate rate (5 x per second): radio failure. Make sure the radio is plugged in correctly, then reboot. If the error recurs, replace the radio. Usually a radio that was plugged in incorrectly will be damaged and must be replaced.
  • Red and Green LEDS flashing alternately slowly (1 x per second): LCOS is running in CONFIGURATION mode. Most normal normal layout functions are suspended.
  • Green LED on steady: LCOS is running in NORMAL mode.

Connecting Peripherals

A Client Node can have multiple DNIN8 boards for inputs, multiple DNOU8 boards for outputs, a PWM driver and the block occupancy detection system. Nodes should be given the peripherals they need, and the mix will vary from Node to Node.

Here is an overview of a Client Node and its connections to peripherals:

A diagram of how a Client Node connects to its peripherals. Click on the image to see full size. Some boards shown are pre-production; the production version of the Client Node has a different terminal layout. See photo below.

There a four sets of terminals for connecting peripherals:

  • On the lower left corner of the LCN, an RJ45 jack for connecting the Client Node to a DNCTA Block Sensor Interface via Cat 5e Ethernet cable. Cat 5e cable is also used to connect the DNCTA with up to 4 DNCT2B Feeder/Sensor modules. For more information see Block Occupancy Hardware Installation.
  • Above the RJ45 jack is a 3 wire terminal for DNIN8 Digital Input duinoNodes. We recommend using 3-wire servo cable for connecting duinoNodes.
  • Above that, at the top left of the board, is a 3 wire screw terminal for DNOU8 Digital Output duinoNodes. In the connection diagram there are two DNOU8 Boards, serially connected. Note that V++ is different on the boards: the board on the left is getting +12volts for V++, while the one on the right is getting +5volts for V++. Relays would be attached to the +5 volt board; lighting and other devices to the +12 volt board. Each DNOU8 board can have any voltage on V++ from 3.3 to 30 volts. The only requirement is all grounds must be tied together.
  • On the bottom row of screw terminals, SDA and SCL are used by the I2C interface. I2C is currently used only by the PCA9685. You can use the +5 volt and ground terminals here to power PCA9685 logic. WARNING: The servo terminals on the PCA9685 must draw power separately from the LCB as shown.
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