Package jmri.jmrix.dcc4pc

Class Dcc4PcBlockLocos

java.lang.Object

jmri.jmrix.dcc4pc.Dcc4PcBlockLocos

public class Dcc4PcBlockLocos
extends Object

Works out which locomotives are in which block from Raw encoding packets.

Channel 1 is a broadcast: every decoder in a block sends its address in the same time slot, so with two locos the ADR_LOW halves collide into invalid codes. Channel 2 is only used by the decoder the DCC packet was addressed to, so a valid channel 2 reply on an input right after a packet to address X means X is in that block. A clean ADR_HIGH + ADR_LOW pair on channel 1 is also accepted, which covers a lone loco the command station isn't addressing.

A loco stays in a block until the block reads unoccupied, or until it has been seen in another block and not in this one for MOVE_MILLIS. There is no plain timeout: a stopped decoder can go many seconds without a channel 2 reply.

A loco that is still present and heard again is reported as a refresh, at most every REFRESH_MILLIS, so its "last seen" time keeps up without flooding the GUI.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Dcc4PcBlockLocos.Change	A loco added to or removed from a block, or heard again in it.

Field Summary

Fields

Modifier and Type	Field	Description
static final long	HEARD_PROVES_OCCUPIED_MILLIS	RailCom from a loco on an input proves the input is occupied, whatever the debounced state says.
(package private) static final int	INVALID
static final int	LONG	Added to an address to mark it as a long (14-bit) address.
static final long	MOVE_MILLIS	How long a loco seen elsewhere keeps its old block, to allow for bridging a gap.
static final long	REFRESH_MILLIS	Shortest time between refreshes for a loco that stays in a block.
(package private) static final int	SPECIAL	ACK, NACK or BUSY.

Constructor Summary

Constructors

Constructor	Description
Dcc4PcBlockLocos(int[] inputs)

Method Summary

Modifier and Type	Method	Description
(package private) static int	address(int high, int low)	Combine channel 1 ADR_HIGH and ADR_LOW payloads (RCN-217 5.2.1).
List<Dcc4PcBlockLocos.Change>	apply(Dcc4PcRawDecoder.Packet p, int[] states, long now)	Apply one decoded packet.
void	clear()	Forget everything, as after a resync: the next packets rebuild it.
(package private) static int	decode(int b)
(package private) static boolean	hasValidReply(int[] ch2)	True if channel 2 holds at least one well-formed datagram or an ACK/NACK/BUSY.
(package private) static String	hex(int[] bytes)
List<Integer>	locos(int input)
static int	mobileAddress(int[] dcc)	The locomotive address a DCC packet is sent to.
static String	name(int address)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MOVE_MILLIS

public static final long MOVE_MILLIS

How long a loco seen elsewhere keeps its old block, to allow for bridging a gap.

See Also:

• Constant Field Values

REFRESH_MILLIS

public static final long REFRESH_MILLIS

Shortest time between refreshes for a loco that stays in a block.

See Also:

• Constant Field Values

HEARD_PROVES_OCCUPIED_MILLIS

public static final long HEARD_PROVES_OCCUPIED_MILLIS

RailCom from a loco on an input proves the input is occupied, whatever the debounced state says. The debounced state lags the raw one (a block becomes occupied after 2 packets, and unoccupied only after 300 ms), so a loco entering a block can be heard before its block reads occupied. An unoccupied reading therefore only removes locos not heard on that input for this long, which matches the unoccupied hold in the sensor manager: a block that has really been empty that long has had no RailCom.

See Also:

• Constant Field Values

LONG

public static final int LONG

Added to an address to mark it as a long (14-bit) address.

See Also:

• Constant Field Values

INVALID

static final int INVALID

See Also:

• Constant Field Values

SPECIAL

static final int SPECIAL

ACK, NACK or BUSY.

See Also:

• Constant Field Values

Constructor Details

Dcc4PcBlockLocos

public Dcc4PcBlockLocos(int[] inputs)

Parameters:

inputs - the enabled inputs, numbered from 1, in the decoder's order

Method Details

locos

public List<Integer> locos(int input)

Parameters:

input - input number, from 1

Returns:

the locos in that block, in the order they were first seen

clear

public void clear()

Forget everything, as after a resync: the next packets rebuild it.

apply

public List<Dcc4PcBlockLocos.Change> apply(Dcc4PcRawDecoder.Packet p,
 int[] states,
 long now)

Apply one decoded packet.

Parameters:

p - the packet

states - the input states to use, debounced, in the decoder's order

now - the time, in milliseconds

Returns:

what changed

name

public static String name(int address)

Parameters:

address - an address as used here

Returns:

it as text, such as "9328(L)" or "3(S)"

mobileAddress

public static int mobileAddress(int[] dcc)

The locomotive address a DCC packet is sent to.

Parameters:

dcc - the packet bytes, without the error byte or with it

Returns:

the address, with LONG added for a long address, or -1 for a broadcast, idle, accessory or malformed packet

address

static int address(int high,
 int low)

Combine channel 1 ADR_HIGH and ADR_LOW payloads (RCN-217 5.2.1).

Returns:

the address, with LONG added for a long address, or -1 if ADR_HIGH isn't a valid address pattern

hasValidReply

static boolean hasValidReply(int[] ch2)

True if channel 2 holds at least one well-formed datagram or an ACK/NACK/BUSY.

hex

static String hex(int[] bytes)

Returns:

the bytes as hex, for the log

decode

static int decode(int b)

Returns:

the six-bit value of a 4-of-8 code, SPECIAL or INVALID