Using STASH to remember where locos are parked

STASH is used for scenarios where it is helpful to relate a loco id to where it is parked. For example a fiddle yard may have 10 tracks and it's much easier for the operator to select a train to depart by using the track number, or pressing a button relating to that track, rather than by knowing the loco id which may be difficult to see.

Automated yard parking can use the stash to determine which tracks are empty without the need for block occupancy detectors.

Note that a negative locoid may be stashed to indicate that the loco will operate with inverted direction. For example a loco facing backwards, with the INVERT_DRECTION state may be stashed by exrail and the invert state will be restored along with the loco id when using the PICKUP_STASH. CLEAR_ANY_STASH will clear all references to the loco regardless of direction.

The following Stash commands are available:

EXRAIL command	Serial protocol	function
STASH(s)	<JM s locoid>	Save the current loco id in the stash array element s.
CLEAR_STASH(s)	<JM s 0>	Sets stash array element s to zero.
CLEAR_ALL_STASH	<JM CLEAR ALL>	sets all stash entries to zero
CLEAR_ANY_STASH	<JM CLEAR ANY locoid>	removes current loco from all stash elements
PICKUP_STASH(s)	N/A	sets current loco to stash element s
IFSTASH(s)	N/A	True if stash element s is not zero
IFSTASHED_HERE(s)	N/A	True if stash element s contains the current tasks loco
N/A	<JM>	query all stashes (returns <jM s loco> where loco is not zero)
N/A	<JM stash>	Query loco in stash (returns <jM s loco>)

Notes: An automatic parking script can run through the various tracks and find one which has no stashed loco, then set the route and drive into the track. Once stopped, the locoid can be stashed against that track.

If the operator wants to drive away a loco manually by loco id, an automation can search the tracks for that stashed loco id using IFSTASHED_HERE(trackid) so it can set the turnouts to exit the yard from that track.