From cbfsb!att!linac!uwm.edu!wupost!cs.utexas.edu!usc!rpi!clarkson!news Wed Oct 16 17:22:51 EDT 1991 Article: 9051 of rec.radio.amateur.misc Path: cbfsb!att!linac!uwm.edu!wupost!cs.utexas.edu!usc!rpi!clarkson!news From: bray@cheetah.ece.clarkson.edu (David Bray) Newsgroups: rec.radio.amateur.misc Subject: Re: IC-735 Request Message-ID: <1991Oct16.141405.9942@news.clarkson.edu> Date: 16 Oct 91 14:14:05 GMT References: <1991Oct15.134207.6539@news.clarkson.edu> Sender: news@news.clarkson.edu Organization: Clarkson University Lines: 107 Nntp-Posting-Host: cheetah.ece.clarkson.edu >From article <1991Oct15.134207.6539@news.clarkson.edu>, by bray@cheetah.ece.clarkson.edu (David Bray): > GOODWIN%SMCVAX.BITNET@mitvma.mit.edu (Dave Goodwin) writes: > >> Having just purchased an ICOM-735 transceiver, I'm interested in finding out >> if anyone has devised the necessary interface between a PC and the rig's >> serial control port? I know Icom makes one, and though I haven't checked the >> price yet I'm sure it will be ridiculously out of line. Thanks. > OK Here is the design -- ICOM Radio/RS232 interface which meets RS232 specifications. *------------------------------------------------------------------------* * This circuit has no expressed or implied warranty of any kind. * * It works very well for my IC-735 and with three different computers. * * It has not been used on any other Icom radio but should be compatible * * with a number of other desktop models. * * BUT * * !! USE IT AT YOUR OWN RISK !! * * D. W. Bray, K2LMG -- Clarkson University * *------------------------------------------------------------------------* This design uses a chip designed to produce both the + and - voltages required by RS232 from a single +5 volts, and incorporates two receiving and transmitting inverters which meet the RS232 specifications. The only other chip needed is a buffer which allows its output to be driven from another source. A circuit drawing is presented below. In words, the implementation is: ICL232 Chip -- Pin 14 is output to RS232 Pin 3; Pin 13 is input from RS232 Pin 2; Pin 11 is tied to 7417 Pin 2 and to a 270 ohm resistor, the other resistor connection is tied to +5V; Pin 12 is tied to 7417 Pin 3. ICL232 Chip -- Capacitors. C3 + lead is tied to Pin 2, C3 - lead is tied to +5V; C1 + lead is tied to Pin 1, C1 - lead to Pin 3; C2 + lead is tied to Pin 4, C2 - lead tied to Pin 5; C4 + lead tied to GND, and C4 - lead tied to Pin 6. ICL232 Chip -- VCC is Pin 16 which is tied to +5V. GND Pin is 15 which is tied to ground. All leads not mentioned should be open. 7417 Chip -- Pins 2 and 3 are tied as discussed above. Pins 1 and 4 are connected together and to the center pin of a 1/8" plug for connection to an Icom radio. 7417 Chip -- VCC is Pin 14 which is tied to +5V. GND is Pin 7 which is tied to ground. All leads not mentioned should be open. The ICL232 chip uses an internal oscillator to create the +- voltages by voltage doublers (which require C1 and C2). Pin 2 is a +10V source, Pin 6 is a -10V source (but are not connect to anything is this design). The Transmitters (Tx) and Receivers (Rx) meet RS232 specifications. One source of the ICL232 is: DigiKey Corp., Thief River Falls, MN 56701-0677 -- 1-800-344-4539. Price approximately $4.80. The 7417 is an open collector buffer chip. This allows a buffer output to be driven from another source, and is compatible with the Icom IC-735 internal pull-up circuit. Designs which use 1488/1489 chips, where the Icom input/output lead is tied to a buffer output (in a similar manner to this circuit), violate chip specifications. In this diagram "+" means "cross", that is, no connection; '*' means connection. .----------. --------------- | .---+-| 1 16 |---- +5V | +| | | | +| C1 --- --| 2 +10V 15 |----- GND C3 --- --- | | --- | | Tx Out 14 |------> RS232 Pin 3 .---> RS232 Pin 7 | ------| 3 | | +5V .-----| 4 Rx In 13 |------< RS232 Pin 2 GND +| | | C2 --- | Rx Out 12 |-----. +5V --- | | | | | | Tx In 11 |--. | R ------| 5 | | | | .------------| 6 -10V 10 | ---+---* ----------- | | 7 | | | .----| 1 14 |--- +5V C4 --- | 8 9 | | -----+----| 2 13 | --- --------------- ---------+----| 3 12 | +| ICL232 *----| 4 11 | GND | | 5 10 | | | 6 9 | C1, C2, C3, C4 = 47 uF | .-| 7 8 | R = 270 ohms | | ----------- | GND 7417 Optional Regulator | ----<> ICOM-Radio ------------- | | 13.8V >-*--| IN OUT |----> +5V | | | C5 --- | | C5 = 0.1 uF --- | | *--| Common | In words: Tie 13.8V to the Input Pin and to a | ------------- 0.1 uF capacitor connected to ground. GND 7805 Tie the Common regulator pin to ground. The Output Pin is +5V. ****************************** D. W. Bray, K2LMG -- Clarkson University -- Potsdam, NY