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Understanding the patch system
Most 'downstream' E-blocks include a patch
system that gives you flexibility in the connec-
tions that are made between the upstream
and downstream E-blocks. The patch system
has two parts: link blocks that dictate whether
the default connections are used or whether
the patch system is used, and the
patch connectors themselves.
Looking at the graphic of the sensors
board in Figure 11:
For this board when the link blocks
are in the default (top) position then
the default wiring is chosen. Default
wiring is optimized for ease of con-
nection between upstream and down-
stream boards for the PICmicro range
of processors. For example the Tx and
Rx lines of the PICmicro are usually
on bits 6 and 7 respectively, so you
will find that the default connections
on downstream boards communica-
tions boards (e.g.RS232 board)
are for bits 6 and 7.
For the Sensor board shown above the
default connections are as follows:
•
Bit 0 LDR (Light Dependant Resistor)
•
Bit 1 RV1 (Resistor-Variable 1)
•
Bit 2 Digital sensors out
•
Bit 3 Analogue sensor
•
Bit 4 Digital sensor in
The bits 0 to 4 have been chosen
because on many devices in the
PICmicro range the A/D inputs are on
bits 0 to 4 of the port.
If you wanted to use another proces-
sor that needed the LDR input on
bit 3 then you would change the link
from the 'default' position to the
'patch' position (bottom) and use a
small jumper wire to make the con-
nection between the LDR output and
bit 3 of the D-type as shown in Figure
13 below. You can see the new block diagram
equivalent in figure 14.
• Get the circuit you want
This technique allows you to get the exact
circuit you want. If you need to copy another
circuit using E-blocks hardware you should
6
Fig 11 - A sensor board
Fig 12 - Sensor board block diagram
Fig 13 - A sensor board in patch mode
Fig 14 - Patched sensor board diagram
find that the patch system allows you to develop
it. Note that the turned pin connectors
on the patch system are compatible with
special prototyping leads: these are a little
more expensive than single strand wire - but
they will last longer and will not break off in
your prototype board or patch connectors.
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