This page contains the documentation portion of the Basic Stamp 2 program that controls the yard and industrial spur turnouts. The complete code and documentation can be downloaded using this link:  YardRoute.zip

' ======================================================================
' YardRoute.bs2                                               9-02-2003
'
' Yard Track Routing and Turnout Control
'
' This program controls the turnouts (Yx) of the yard and approach tracks
' on the D&B model railroad. Multiple keypads are positioned on the layout
' for the purpose of setting the route a train will follow. Any keypad can
' be used to set a route based upon the input of two track number values.
' The following diagrams the track and turnouts involved.
'
'                             ~
'                             | T7
'    /------------------------|\-------------------------------------\
'   /                                                                 \
'  1              \                   /     /   /   /    /   /   /     2
' /                \                 /     /   /   /    /   /   /       \
' \                 \               /     /   /   /    /   /   /        /
'  \                 14            15    6   7   8    9   10  11       /
'   \                 \           /     /   /   /    /   /   /        /
'    \   ------- 13 ---\Y18   Y15/--Y16/   /   /    /   /   /        /
'     \                 \       /     /   /   /    /   /   /        /
'      \    ---- 12 --Y17\-----/     /Y12/Y11/    /Y13/Y14/        /
'       \                           /            /           Y3   /
'     Y1 \---------Y5\-----------Y9/--- 5 ---Y10/----/Y8-------/-/ Y4
'         \   Y2      16                            16        / /
'          \-\---------\Y6------------- 4 -------Y7/---------/ /
'             \                                               /
'              \----------------------- 3 -------------------/
'
'
' Operational Requirements:
'
' All yard and approach tracks are assigned a number; 1 through 16. The
' numbered keys of the keypad correspond to the numbered tracks. A route
' is specified by keying in two track numbers. The first number entered
' is the "from" track. It is the track currently occupied by the train.
' The second number entered is the "to" track. It is the desired destin-
' ation track for the train. Once both numbers are keyed in, turnouts
' for the specified route will be set appropriately. Key combinations
' that do not correspond to a valid route will be ignored and a warning
' tone will be sounded.
'
' Keying in the same number for the "from" and "to" tracks will set the
' turnouts to route just the specified track. This is also useful for the
' following operations.
'
' Track 4 or 5: Will set all turnouts on both of these tracks to their
'               normal (straight) position.
' Track 16:     Will open the four turnouts Y5 through Y8 for a "run
'               around" operation.
'
' There are two special cases that must be handled. For a track 4 to 5 or
' track 5 to 4 request, the turnouts used are train direction dependent.
' Since the train direction is not known, the code initially sets turnouts
' 5 and 6 for track 4 to 5 and turnouts 7 and 8 for track 5 to 4. If the
' same track command is consecutively entered, the code inverts the
' settings of turnouts 5/6 and 7/8.
'
' The approach and yard tracks form a reverse loop which is electrically
' isolated from the mainline. The polarity of this loop is controlled by
' the ReverseLoop.bs2 program based upon the position of wye turnout T7
' and the train sensors associated with it. Refer to the ReverseLoop.bs2
' program for details on its operation. Since there are no reverse loops
' within the yard tracks, no power polarity control is required.
'
' Position feedback information is not used for the yard turnouts since
' no automatic turnout positioning functions are performed by this
' program. Only the turnouts for the selected route will be affected.
' The program remembers turnout positions as they are set during oper-
' ations. This information is referenced during subsequent operations
' to skip the setting of turnouts already in the proper position. No
' default turnout positions will be set or assumed at power up.
'
' To facilitate keypad entry, an indicator is positioned next to each
' keypad. This indicator will be illuminate when the first track number
' is entered. It will extinguished when the second track number is
' entered.
'
' Hardware Description:
'
' Refer to schematic page 3 for the hardware circuitry associated with
' this description.
'
' This program utilizes the Basic Stamp 2 micro controller which has 16
' I/O bit positions. External interface chips (74C922) are used to
' encode and debounce the keypads. Output multiplexors (74154) are used
' for interfacing the turnouts. Two output bit positions are assigned to
' control each turnout. See constant definitions below. The cross over
' turnouts Y5/Y6 and Y7/Y8 are wired for controlled by a single pair of
' bit positions since both turnouts must always be changed together.
'
' Turnout operational current requires that a driver circuit be used
' for each turnout coil. When a turnout is to be positioned, this program
' pulses the appropriate output bit for a nominal 200 ms. This causes the
' driver to energize the turnout coil.
'
' An output pin of the Basic Stamp is connected to a speaker and used
' to sound warning tones. A warning tone is output when an invalid route
' is specified.
'
' An output pin of the Basic Stamp is connected to a Led and used to
' indicate operation (heartbeat). Flashing indicates that the code
' is cycling in the main program loop.
'
' Two output pins of the Basic Stamp are each connected to a Led and used
' to indicate the state of entry for the track numbers on each keypad.
' ======================================================================
      

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