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Part 2: Interfacing and Configuring
Logic Level Shifting and Conditioning Circuit
The following circuit diagram is of a Logic Level shifting and conditioning circuit. This circuit should be
used if you are making your own parameter cable and are using a laptop computer with 3.3 V output parallel
ports.
U1:A
U1:B
U1:D
U1:C
HCT125
HCT125
HCT125
HCT125
2
1
14
4
5
7
13
12
11
10
8
9
6
3
2
R1
100
+5V
R2
49.9
P2: 8
CLK
+5V
P2: 4
P2: 7
P2: 10
P2: 6
P2: 5
CS
MOSI
MISO
+5 VDC
GND
5
6
10
7
4
8
3
4
19
DB25: 2
DB25: 3
DB25: 4
DB25: 19
DB25: 15
15
C3
330pF
R9
100K
R10
100K
R4
49.9
R6
49.9
C4
330pF
R3
100
R5
100
C5
330pF
R11
100K
+5V
R12
100K
+5V
R8
4.9K
R7
49.9
+5V
C1
C2
.1µF
1µF
25V
+
Figure 2.4.2: Logic Level Shifting and Conditioning Circuit
NOTE: If making your own
parameter setup cable, be
advised the 3.3V output
parallel ports on some
laptop PC’s may not be sufficient
to communicate with the device
without use of a logic level shifting
and conditioning Interface.