Hardware Support: XpressNet - Lenz Feedback Bus Addressing

On Lenz systems, feedback from input devices is handled by the Feedback Bus. The input available from the feedback bus is provided by the Lenz LR100 and LR101 Feedback Encoders, or Lenz accessory decoders which provide feedback capabilities (the LS100 for example).

Adding an item to the table

When you add an item to one of the tables, many times you only have to fill in the numbers to have JMRI construct the complete system name.
Here's a summary, split up for outputs (eg. Turnouts) and inputs (eg. Sensors):

In/Out	Entry	Meaning	makes System Name	Minimum	Maximum
in	3	Feedback module 1, input 3	XS3	1	1024
in	99:3	Feedback module 99, input 3	XS787	1	1024
out	3	Turnout 3	XT3	1	1024

Addressing Accessory Decoders with XpressNet in JMRI

Each accessory decoder is addressed by giving it an address in the address space allocated by the NMRA for accessory decoders. This allows accessory decoder addresses from 1 to 1024.

In JMRI's tools, you can prefix the address with XT to tell system the decoder is accessed via an XpressNet based system. If you only have an XpressNet based system configured, you can just use the address, and the programs will automatically assign an XT prefix for you.

On the Feedback bus, accessory decoders are allowed to occupy addresses from 1 to 64. Since the feedback equiped decoders Lenz provides actually include 4 accessory decoders, this limited address space actually corresponds to accessory decoder address 1 to 256.

To calculate what feedback device Addresses one of your accessory decoders resides at, round up to the next multiple of 4, and divide that number by 4.

For example, if you have an accessory decoder with address 121, the next multiple of 4 is 124. 124 divided by 4 is 31, so this decoder is included with feedback address 31.

Feedback from accessory decoders is handled automatically by the turnout tools included with JMRI. If the turnout is equiped with feedback, the Turnout Tool, Turnout Table, or a control panel will not update the turnout's status until a response from the feedback bus indicates the turnout has been thrown.

Status for decoders that do not report feedback is handled by waiting for a response message before changing the decoder's status.

Addressing Lenz Feedback Bus Sensors in JMRI

The Lenz LR100 and LR101 Feedback Encoders are allowed to have feedback addresses from 1 to 128. Lenz Recommends starting at address 65 and going up to avoid conflicts with turnouts providing feedback.

NOTE: the LR100 actually has 16 inputs, and does take up two addresses.

Each feedback encoder includes 8 inputs. These inputs are either either On or Off. Each input is numbered from 1 to 8 on the Feedback Encoder.

To determine what feedback address is being reported by the device, you need to know the address of the feedback encoder, and which input you are using. See Lenz's documentation for determining how to program the Feedback Encoder's Address. This can be done with the encoder in place on the layout.

To calculate the address of a sensor, subtract 1 from the Feedback Encoder's address, multiply that result by 8, and then add the input number you are using.

For Example, if you are using contact 3 on a Feedback Encoder with address 99, 99 - 1 = 98. 98*8=784. 784+3=787. The feedback address you will use is 787.

In the hardware address field of the "Add Sensor" pane you can enter in the encoder address, followed by the contact separated by a ":"
So for a sensor on feedback encoder address 99, contact 3 you would enter 99:3

In JMRI's tools, you can prefix the address with "XS" to tell the program the Sensor is accessed via an XpressNet based system. If you only have an XpressNet system connection configured, you can just enter the address, and the programs will automatically assign an "XS" prefix for you.

Back to the XpressNet Help page

Paul Bender
paul.bender@acm.org