GENERAL
INTEREST
36
Elektor Electronics
11/2002
Even shortly after the introduction of EEDTS
Pro, it was evident that some users needed to
be able to control the system without using a
PC. One of the most frequently asked ques-
tions was whether the earlier EEDTS keypad
could also be adapted to be used with the
system and whether a keypad control would
be coming. Another question that arose with
regard to stand-alone operation of the con-
troller was whether the ‘fixed’ addresses of
the manual controllers could be changed
without having to use a PC.
You might think that it shouldn’t be so dif-
ficult to add these functions to the controller,
but as can be seen from the old EEDTS
address programmers and keypad circuit,
such circuitry uses quite a few processor I/O
lines or special I/O components.
That leads to another problem: practically
all of the I/O lines of the EEDTS Pro controller
are already in use, and the few that are not
used are not routed to external connectors.
The question was thus whether it was nev-
ertheless possible to implement the above-
mentioned functions within the current con-
cept.
The solution was found in the S88 bus.
This controller interface, which is quite busy
collecting return data via the track when PC
control is used, has precious little to do in
stand-alone operation. That forms a good
argument for using it for our purposes, with
the additional advantage that absolutely no
changes are necessary on the main controller
circuit board. At the same time, we
immediately gain access to 64 8-bit
input channels, which is more than
sufficient for our plans.
Starting up in stand-alone
mode
The controller cannot decide on its
own whether stand-alone or normal
operation is desired. Its preference is
for normal operation, in which all 64
EEDTS return signallers (or 32
Märklin S88 modules) are seen as
return signallers (with addresses
1–64) that can be queried via the PC.
However, if the F0 key of manual
controller 1 is held pressed while the
main controller is started up or reset,
the interpretation of the S88 bus
changes as follows:
– the first 32 (8-bit) modules are
Stand-Alone
EEDTS Pro
with controller addressing circuit
By S. van de Vries
Not every user of the EEDTS Pro system needs to control his model
trains using a PC. This article describes how the system can be used
stand-alone and what is required. We also present a deluxe address
programming circuit for your manual controllers.
Summary of Contents for EPROM
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