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Understanding the patch system
Most 'downstream' E-blocks include a patch
system that gives you flexibility in the
connections 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 1:
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 connection between upstream
and downstream 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
communications 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 Dependent 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 processor 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
connection between the LDR output and bit
3 of the D-type as shown in Figure 3. You
can see the new block diagram equivalent
in Figure 4.
• 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
find that the patch system allows you to de-
velop it. Note that the turned pin connectors
6
Figure 1 - a sensor board
Figure 2 - sensor board block diagram
Figure 3 - a sensor board in patch mode
Figure 4 - patched sensor board diagram
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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