Introduction

This page is just a small collection of other CI-V interfaces that can be readily built and used. On the Digital Modes page, I have a drawing for the CI-V interface that I built and use. So I won't be including it here.

Other RS-232 to CI-V Interfaces
RS-232 SignalState
-3 to -25 Volts1
+3 to +25 Volts0
RS-232 ControlState
-3 to -25 VoltsOff
+3 to +25 VoltsOn
CI-V SignalState
> 2.0 Volts1
< 0.8 Volts0
DTE Signal Source
"Computer End"
DB25DB9Signal
81DCD
32RXD
23TXD
204DTR
75GND
66DSR
47RTS
58CTS
229RI

Since my original build, I have come across several other interfaces that would probably work as well as the one I built. Of course, eveyone lists a disclaimer, including myself, that the circuit works fine for them, but doesn't come with any liabilities or guarantees. I am not going to say much about each one, except for a few notes. Where possible, I provided links to the original web page.

The IO connector labeled CIV I/O, in the diagrams below, is a 3.5mm Phone Jack. To connect to the radio's CI-V input, use a shielded cable with a 3.5mm Phone Plug at each end. You could also eliminage one Phone Jack and one Phone Plug and tie the open end of a cable directly to the circuit. The other end of that cable would then have a 3.5mm Phone Plug.

None of the circuits should be picky about the transistors used. You should be able to use a 2N2222, 2N3904, or any other generic switching transistor.

Some of the circuits use a DB9 connector and others use a DB25. The signal lines, including ground, will be on different pins. Note that the RxD and TxD signals on the DB9 connector are swapped on the DB25 connector.

OK2WY Bare Bones Interface
OK2WY Bare Bones Interface
1
2
3
4
5
6
7
8
9
RS-232
DB-9
D1
1N914
+
C1
10µF/16V
R1
10KΩ
D2
1N9148
Q1
BC337
R2
4.7KΩ
R3
4.7KΩ
R4
4.7KΩ
Q2
BC337
CIV I/O
Added Circuitry for PTT
5
7
RS-232
DB-9
R5
4.7KΩ
R6
4.7KΩ
D3
1N914
Q3
BC337
D4
1N914
PTT
GND

On the left is a Bare Bones circuit by OK2WY. While this circuit doesn't conform exactly to the RS-232 specification, it does work well and has the advantage of being easily constructed inside a 9 pin D-type shell. The circuit is powered by DTR (pin4). This interface has been successfully used directly from a Serial Port and from a USB to Serial Port Converter Cable. If a PTT function is required from the COM port, pin 7 (RTS) can be used to provide this facility.

OK2WY with Input Changes
1
2
3
4
5
6
7
8
9
RS-232
DB-9
D1
1N914
+
C1
10µF/16V
R1
10KΩ
D2
1N9148
Q1
2N2222
R2
4.7KΩ
R3
4.7KΩ
R4
4.7KΩ
Q2
2N2222
CIV I/O

This circuit on the right is also used by David Aldridge, G3VGR. It is almost exactly the same as the interface above, by OK2WY. The only difference is that Pin 7 (RTS) and 8 (CTS) are tied together. And the power connections have changed, tying pins 1 (DCD), 4 (DTR), and 6 (DSR) together (Anode of D1).

You might also note that 2N2222 transistors are used in place of the BC337s. The transistor type is non-critical.

Super Simple RS-232 to CI-V Interface
RS-232 to CI-V Interface, by G3MCS
1
2
3
4
5
6
7
8
9
RS-232
DB-9
R1
10K
R2
47K
R3
47K
Q1
BC172
Q2
BC172
Q3
BC172
CIV I/O
CW Key

This is a super simple RS-232 to CI-V interface from Bill Hawthorne, G3MCS. Its made with three NPN transistors and three resistors. If you don't want the CW Keying interface, you can eliminate one transistor (Q3), one resistor (R3) and the associated output connector for keying. The circuit takes the RS-232 unidirectional RX and TX signals and combines them into a two wire bidirectional open collector bus. The circuit can easily be built directely into a RS-232 DB9 or DB25 shell.

Note that the original circuit used a DB25 connector. I changed it to a DB9 so that it is consistent with the other drawings on this page.

The transistor types are non-critical. A BC547B, 2N3904, or 2N2222 would probably work fine. The cable for CI-V communications, from the interface to the radio, should be shielded cable. Shielded audio cable should work fine, but a short piece of thin flexible coax might work even better.

Isolated RS-232 to CI-V Interface by Gary Dion N4TXI
Isolated RS-232 to CI-V Interface, by Gary Dion, N4TXI
DB9
7
RTS
4
DTR
2
RxD
3
TxD
5
GND
D1
1N4148
D2
1N4148
R1
10K
R2
2.2K
R3
3.9K
R4
2.2K
R5
100K
R6
2.7K
+
C1
1 uF
+8V
1
2
4
5
6
4N28
U1
1
2
4
5
6
4N28
U2
Q1
2N3904
CIV I/O

There are even simpler designs available, such as this opto-isolated model by Gary Dion N4TXI:

In situations like field day, when rig grounding may be questionalble, this interface is a good option

This design draws an average of less than 0.5 mA. The power supply can be taken from either the ACC connector or the microphone jack.

ICL232 RS-232 to CIV Interface
RS-232
to
CIV Interface
C1+
C1-
VS+
C2+
C2-
VS-
TTL - RS232
T1
T1
T2
T2
R1
R1
R2
R2
1
3
2
4
5
6
11
14
10
7
12
13
9
8
ILC232
U1
VCC
GND
U1 - ILC232
16
15
+
C1
47uF
+
C2
47uF
+
C3
47uF
+5V
+
C4
47uF
1
2
3
4
5
6
7
8
9
RS-232
DB-9
1
2
SN7417
U2-A
R1
270Ω
+
5
V
3
4
SN7417
U2-B
J1
ICOM CIV

The drawing on the right is a RS-232 to CIV Interface. It uses a ILC232 chip which is capable of producing its own "+" and "-" RS-232 voltages. These internal voltages are used with the transmit and receive buffers. T1 and T2 accepts TTL level signals and output RS-232 level signals. T3 and T4 accept RS-232 level signals and output TTL level signals.

While a ILC232 IC is used, the same functionality can be had under other names (e.g. MAX232).

This design is difficult to associate with any particular person. The data sheets for this device, and the MAX232, provide all of the information you need to implement the interface. I have even come across this same design done in ASCII text.

The circuit is meant to run from a 5 VDC power supply. If you are using a higher voltage, like 9V or 13.8V, you will need to add a three therminal regulator. Something like the ML7805, and a few capacitors, will work fine.