ProTrak^[TM]
(for MS W98, W95, NT4.0, 2000, ME, XP)

The Grapevine^[TM]  

Description, Message Format and Protocols

• Simple electronics: plug and click connections, pre-assembled boards
• Complete! Software includes the knowledge you want for prototype signaling!
• Affordable! Lowest cost system available
• Fast to install! Have your signals working over the weekend.
• Open, non-proprietary format.  Use these Grapevine Network commands to write your own software

• The Grapevine is a serial network, using the RS-422 electrical specification.
  • This allows long transmission lines (thousands of feet).
  • It can be used in a noisy electrical environment (a model railroad).
  • Transmission is presently at 38,400 baud
  • The basic message is 4 bytes: address + data + address + parity.
  • One serial port on your computer is used for each Grapevine loop of up to 127 nodes.
  • A Grapevine Node is a board with a microprocessor that:
    • decodes addresses for incoming messages
    • converts voltage levels from devices to messages
    • encodes addresses and data for outgoing messages (detectors)
    • includes code to drive analog and digital fastclocks.
    • includes code to run highway crossing flashers and gates
    • includes code to generate DCC packets
    • includes code to address an ordinary printer.
    • Special dedicated nodes are used for the Working Weighscale.
  • Each Grapevine Node has its own unique address, which is can be re-programmed from ProTrak (or your software).
  • Additional Grapevine circuits can be added, using additional serial ports on the host computer(s).
  • Other computers can be attached to the Grapevine, however a dedicated conventional LAN is recommended for multiple computer systems.
• The Grapevine system includes other hardware:
  • driver board that controls multiple aspect signals (red, green, yellow, off, flashing red, flashing green, flashing yellow).  Can drive
    • searchlight signals with bi-color leds
    • 3-led color signals
    • Pennsy and CPL signals
    • semaphores (special board)
  • driver board can drive switch machine motors
  • detectors optimized for DCC (but also can be used for Railcommand)
    • eight-detectors per board, connects to Node serial port 
    • up to 3 Advanced Serial Detectors (ASD) can be daisy-chained per Node
    • up to 16 "parallel/analog" detector inputs per Node
  • a Working Weighscale
  • digital display board, for a digital fastclock or a hotbox axle counter display
• The Grapevine system also can control, or receive data from:
  • relays
  • on/off switches
  • infrared (IR) spot detectors
  • any other device that needs a logic signal
• Each Grapevine Node can:
  • drive 48 signal leds
  • receive data from 24 serial detectors and 16 "parallel/analog"detectors
  giving you the ability to control up to 6048 signal heads and 5080 detectors on each serial port.
  • be configured to drive various combinations of leds, switchmotors and detectors.
• The Grapevine uses a very simple data transmission protocol.
  • The nodes are daisy-chained along the Grapevine so that every node receives all the messages.
    • Bytes are examined and if destined for that node are extracted and acted upon by the node.
    • Otherwise bytes are sent to the next node.
    • Outbound (e.g. detector) messages are added into the data stream by each node.
    This is very similar in concept to the original AppleTalk network and to the MIDI standard for electronic music.
  • Data collisions are avoided by specifying that any program activity on each node must occur within 520 us, the time it takes to transmit or receive one byte (plus start and stop bits).
    Note: ProTrak/Grapevine microcontroller programs are 100% interrupt driven which largely removes the 520 us limitation, except for the interrupt handlers themselves.
  • Messages are sent out over the Grapevine in two serial bytes.
  • The first byte is the address of the Grapevine node that the message is for.
  • The second byte contains the data that is
    • interpreted by the node.
    • sent by the node
  • The third and fourth bytes contain parity information (to confirm message integrity)
  • Multi-byte messages possible
• Electrical
  • The cabling between nodes is standard 6-wire phone cable.
  • The Grapevine nodes use RJ-12 plugs and sockets.
  • The outer 2 wires are ground.
  • The inner 4 wires, in 2 pairs, carry the RS422 signal.
• It is that simple!

The Grapevine is an open system.  We publish the Grapevine Network formats to make it an open system so as to encourage development of other Grapevine hardware and software by independent third parties.  The purpose of this note is to disclose enough information so that you can:

• make your own Grapevine devices.
• write your own Grapevine controller data acquisition software.

• Grapevine message format protocol page 1
• Grapevine message format protocol page 2
• Grapevine message format protocol page 3
• Grapevine message format protocol page 4
• Grapevine message format protocol page 5
• Grapevine message format protocol page 6

This page last modified: March 27th 2005