‘ARDUINO UNO’ Desires Conversation With IC-7700, For Amplifier and Tuner Control Fun


Jeff  VE1ZAC                   April 30, 2011


I thought I was making my shack  and rig more convenient and more efficient for DXing and contesting. For unsound financial and ‘need’ reasons, a nice new solid state amp to replace my venerable homebrew 600 watt amp seemed like the perfect spring ham project.

The Ameritron ALS-1300 caught my eye and I decided to give one a whirl. While I was at it, it seemed like a perfectly good idea to order a high power auto tuner to go with it, and an MFJ-998 joined the procession. After dealing with the problems of ordering from MFJ’s factory supply chain, I was told by a nice lady at Ameritron that most of their inventory is carried by dealers. It took 2 months to discover that.  One day later, DX Engineering had one shipped to me !


A nice feature of solid state amps is the ‘no-tune’ power mosfet PA design, although you have to load it with a pretty darned good match. So, a decent matching device is a necessity around my shack. The 998 is an auto-tuner and advertised as having a built in radio interface.. oh boy ! It also can control the rig –amp key line to insure the amp is put in standby on a tuning cycle. This radio interface, and the band switch adapter I ordered for the amp should allow seamless interfacing with the IC-7700 or other rig I might want to hook up to it. Right ? Wrong ! Nothing is that simple, as we all know.


Problem number 1

The MFJ radio interface is the well known, ultra reliable and ubiquitous AH-3/4 interface that is included with every Icom HF ham transceiver since the bronze age. Except… the IC7700 and 7800. Some Icom marketing genius ( probably a committee with a locked down QA process) decided that the external tuner interface would no longer be required with these rigs. I can’t even guess what twisted logic produced that one. But, we 7700 and 7800 owners don’t have it  … no easy remote tuner hook up for this interface.


What is this interface anyway?  When a properly interfaced remote tuner is plugged into the port on any other Icom HF rig.. the rig’s software detects it and causes a new set of commands to be run when the rig’s TUNE button is engaged. Normally, the rig goes to low power, switched to AM, calls the remote tuner to engage, accepts a TX command from the remote tuner, and allows the tuner to do it’s tune cycle. When that is done, the tuner tells the transceiver to go back to receive, go back to whatever mode it was in, and put power back where it was.  It’s actually about 6 steps. And it works beautifully.


One the other hand, I have an interface plug and a radio with no interface. So.. how do I join these guys ?


The DXLab Commander Solution

Dave Bernstein’s Commander (which is an integral part of my station) has a very workable method of creating macros to attach to custom push buttons in the Commander window. I spent quite a bit of time working with this and pestering Dave into helping out. As usual, he sends along the relevant info when you need it. I hope he finds this entertaining. I would probably find it irritating.  I started out with the belief that I could deal with the tuners need to control the TX process. The only hope was to use the LPT port which can work with some Commander macro commands. But after spending many hours fooling with this I had to give it up. One problem was the laptop I use for a station computer. Like most laptops today, there is no LPT port. And the USB-LPT adapters for printers do not allow “Bit-banging” the data lines that you can do with an old fashioned embedded LPT port. I did find a PCIexpress card LPT adapter that did work after a fashion, but you couldn’t control a bit well enough for the tuner needs. I abandoned that idea. I did, however, create a couple of little macros that would do the job and work with the tuner without the radio interface. But you have to be careful to take the amp offline first.

I made 4 macros:


1) Set the rig up for amplifier use. Low power, CW, Ant4 ( which is where I drive the amp), turn auto tuner off, turn tuner start off.

2) Do all of 1) and do a timed  AM, low power TX.

3)  Do all of 2), but deal with a split VFO mode. In this case, I swap VFO’s, turn split off, do the tune, and put it back.

4) Revert rig back to regular ( non amp) CW mode.


NOTE: I only use CW, so I didn’t bother with any SSB interaction, but one could easily do that.


This worked pretty well, but you have to be careful. However, I still wanted the full auto deal and looked for another solution. Actually, it’s one I had in the wings anyway.


Yup, it’s time for an Arduino to hook-up with an Icom !


The ARDUINO Solution

If you don’t know what this is, GOOGLE it, and be amazed. This is the hottest little development board around and is perfect for gazillions of amateur radio projects. And dead easy to use. And cheap! The programming environment is open source and java based and runs on anything. There are hundreds of websites and learning opportunities on line, so I won’t re-invent the wheel here. I have used them for a couple of other projects and for a couple of work related projects and find they are everything advertised, and more. The basic board has everything you need on board including 14 digital I/O pins, a hardwired serial port, programmable serial ports if you need them, 6 A/D  I/O ports… etc, etc. It self powers from  USB port to your computer, and when done, you just plug it into whatever DC source over 5Volts you have around. It boots on power up. And anytime you want, you just plug a USB cable back in for tweaking code, monitoring things, etc.

The Arduino homepage:  http://www.arduino.cc/


This is the popular ‘UNO’. It can store 32K of program and data in it’s EEPROM.


They run around $30,  and can be had from many sources. I like SparkFun Electronics and CanaKits for Arduino supplies. If you get one to play with, it is a really good idea to get at least one of the little experimenters ‘Shields’ that plug into the top of the board and allow quick experimenting. (You will see one in my setup a little further along.)


Writing Code: Caveat Emptor.. I am not a professional coder. I can do what I need to do and have written code in various languages and platforms for the last 35 years, but ‘I ain’t no expert’. I am sure almost anybody could do this better than me. But, I have included the project code at the end, if you want to wander through it. Arduino language is almost like C++.


Some requirements for the code:

  1. Receive data  and transmit Icom commands from/to the IC7700 via the CI-V serial buss line, at 19200 baud. (√…. Means this is done)
  2. Transmit  whatever Icom command is needed from a command table in the code. (√)
  3. Test the rig for split VFO’s (√)
  4. Work with the tuner to start the tune cycle and receive and forward the 998 tuner TX command to the IC-7700 as needed. (√)
  5. Auto setup the rig to work with the amp as required. (√)
  6. Wait for a Tune cycle call from a manual pushbutton located near the tuner. (√)
  7. Provide a little panel feedback through a red and green LED. (√)
  8. Allow easy access for software tweaks and changes (√)
  9. Provide a delayed power up function on the tuner interface line, to simulate a real radio being attached. (√)
  10. Power from the amp/tuner combo. ( more on this in text) (√)
  11. Organize auto band changes to the amp from the IC700 (not done yet, more in text)
  12. Operate reliably (!)  ( probably not there yet, although it does work. There are a few odd occurrences with the tuner occasionally, that need some tweaking, nothing that is dangerous though.)


OK, I got through the requirements list and used about 15% of the space in the EEPROM.  You can look at the code at the end, if you are adventurous. I have some half baked comments in the code, but they need updating as well. You will see a lot of rem’d (// prefix) lines involving printing. These allow important variable to be displayed on the Arduino serial port monitor when you have a computer hooked up, and are for debugging. They aren’t need for normal operation, so they are turned into comments.

Sending commands to the IC-7700 is straightforward. Reading data from the rig is the trickier operation.



I put everything in a small die cast box that allowed two cover screws on the amp to be used to hold it in place. I also tapped into the 12 volt DC supply in the amp to provide external 1 amp PTC fused power for the tuner and for this device. It all comes alive when you turn the amp on. Amp is ready to roll in about 8 seconds.. pretty cool for a fast QRO when needed.




I only had a black push button in the shop.. an unfortunate choice for  photographing. It will look better with a label. The box on the right houses the device. Too bad MFJ and Ameritron didn’t select a common width for these two products.. they would stack a lot better.  I suspect they are often used together. I put some extra stick on feet on the tuner so it sits on top fine.


Looks kind of like an InookChook, don’t you think ?


The ARDUINO – CIV circuit

This needed a bit of thinking. The Arduino is a 5 volt supply circuit. And the serial pins are also 5V+ to 0 V levels. The CI-V interface should be fairly straightforward and I discovered an article where an open gate buffer was used for this purpose. I didn’t have any TTL or LS devices around like that, but did have a SN7405N which is a hex inverter with open gates. This should work fine, but you need two inverters in series to get a buffer  with no inversion function. No problem. Open gates require a pull up resistor. Unfortunately the 1 K resistor I used on the gate output going to the Arduino also caused some USB problems. The Arduino shares the USB port on the ATMega386 processor chip with a USB FTDI chip. The 1K resistor pulled the port too high for USB downloads. No problem, I added a switch in the line which is only needed when you download new code. Normally it is left closed. SN7407 and SN7417 are open gate buffers, or you could use pretty much any LS or other variant of these things.

I also paid a lot of attention to RF filtering on everything going in and out of the box. So far, no RF feedback problems. Here are some construction pictures and the schematic of the interface:

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The Arduino with a Spark Fun experimenter shield





The back with the interconnections. The molex connector is a surplus computer power connector modified to look like the Icom AH-3 plug.


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On the side of the rig.


The schematic:

And, the operating position with everything buttoned up





What’s left?

The auto band switching.. that’s what. The amp came with a little interface that actually does decode the IC band data from an auxiliary connector on the back of the rig. Problem is… it disables the amp standby switch for some reason. I was pretty disappointed with that. I think it is essential to have that switch. I notice Phil Silas has a mod for that on his web site and that might be the solution. Or, I could add code to the Arduino to read the band switch and control the amp. Both can be done. I will probably try the amp interface modification first, and if that doesn’t work out, then go to the Arduino code.



The code:  Here it is.. read it and weep !

If you decide you want to play with this, email me and I will send you the file. Or I might post it in the file section for either the IC7700 Yahoo group or the DXLab Yahoo group if Dave Bernstein thinks it is OK to do that. If you are the code type but don’t have experience with the Arduino, have a quick look at the website for the Arduino wiki reference.. it gives a basic overview of what’s going on.


//the AH-4 tuner function for Icom CI-V and MFJ 998 control

//commands work with Icom interface enabled in 998 tuner

//and Icom CI-V line with Arduino processor

//reads key line from tuner

//controls start line and radio Tx and Rx


// define the pins we need for interfacing

//LED is to show STARTTUNE running

// Use a delay when turning split on and off before proceeding as rig

//is slow to respond

#define TUNEBUTTON 8/ / the PB on unit to start process

#define LEDKEY 13/ / LED pin,

#define LEDTUNE 12/ / LED pin,

#define KEY 9/ / t u n e r t x switch, normally high off

#define TUNESTART 10/ / S tart on tuner cable, normally high off

#define TUNEPOWER 11/ / delayed response to simulate radio


// These are all the command arrays needed

//array elements are DEC versions of HEX command

// add more as needed and transmit in byte array loop

int tx[8] = {254,254,110,224,28,00,01,253}; // turn tx on

int rx[8] = {254,254,110,224,28,00,00,253}; //goto receive

int dis[8] = {254,254,110,224,28,01,00,253};/ / disable tuner

int toff[10] = {254,254,110,224,26,5,0,113,0,253}; // disable tuner auto

int lp[9] = {254,254,110,224,20,10,0,101,253}; // set rig to low power

int amlp[9] = {254,254,110,224,20,10,0,144,253};// set at 80 for AM

int am[7] = {254,254,110,224,6,2,253};/ / AM mode

int cw[7] ={254,254,110,224,6,3,253};/ / CW mode

int ant4[7] ={254,254,110,224,18,3,253};/ / use ant 4 position for amp

int hp[9] = {254,254,110,224,20,10,2,85,253}; //back to high power

int tun[8] ={254,254,110,224,28,1,1,253};/ / e n able tuner

int ton[10] = {254,254,110,224,26,5,0,113,1,253};/ / e n able tuner auto

int splitoff[7] = {254,254,110,224,15,00,253};

int spliton[7]= {254,254,110,224,15,01,253};

int swapab[7]={254,254,110,224,07,176,253};/ / swap VFO A and B

int split;// split indicator, 1 or 0

int splitmarker;

int buffcall[6] = {254,254,110,224,15,253};/ / command 0F buffer

int buffget[7] ; // the receive buffer

// some control variables

int i;

int incoming;

int value;

int value2;

int valuekey;

int old_value = 0;

// This loop run once on start up to set up things

void setup() {



pinMode (KEY,INPUT);





digitalWrite(TUNEPOWER,LOW); // delay showing +V line on tuner for 5 seconds



digitalWrite(TUNESTART, HIGH); // be sure TUNESTART pin is high

digitalWrite(LEDKEY, LOW);

digitalWrite(LEDTUNE, LOW);



void loop() {

//start the split detector here



for (i=0; i<6; i++) {

Serial.print(buffcall[i],BYTE); //send command to ask for split, 0F


//delay(5); // give a delay from radio to respond


if (Serial.available() >0) {

incoming = Serial.read();

if (incoming == 254) {/ / 1st byte is an FE look for an FE to start

goto start; }

goto next; }


//Serial.println(" ");


for ( i=0;i<6;i++) {/ / g et next 6 bytes

if(Serial.available() >0) {

buffget[i]=Serial.read(); // load buffget with next 6 characters

delay(2);} //delay 2 ms if true.time for buffer fill

} / / OK, got new 6 byte buffget array

if (buffget[3] == 15){ // check to see if 4th char is 15

goto next1; }/ / 0 F detected , go to next1

goto listen;/ / wrong array, get another



//Serial.print (" split present = "); // We have an array

// Serial.print(buffget[3]); // print the 0F , or 15 to be sure

if(buffget[5] == 253 ){ //look for an FD at end of array

goto maybe; } // if fd detected, goto maybe

goto listen;/ / wrong command



//Serial.print(" maybe split= "); //have an array that should have a 15 in it

//Serial.print(buffget[4]); // print the split data

if(buffget[4]== 0) {


goto finish; }

if (buffget[4] == 1) {


goto finish;}

goto next;/ / not valid split status.. go again



//Serial.print(" finish = ");

//for( i=0;i<6; i++) { // buffer will be missing first FE

//Serial.print(buffget[i],DEC); // print out entire buffer

//Serial.print(" "); }

Serial.println(" ");

Serial.print(" Split status is ");


// now wait for tune button


//digitalWrite(TUNESTART, HIGH);



value = digitalRead(TUNEBUTTON);


if ((value ==HIGH) && (old_value ==L OW)) {/ / wait for TUNEBUTTON to push


if(i > 1000){/ / if nothing happens in 1 sec, check split again

goto listen; }

goto wait5 ;


old_value = value;

//Serial.println(" start button pushed");

// decide on what to do about split

if(split == 0) {

splitmarker = 0; //no split, carry on

goto vfogo;}/ / s p lit must be off

// split must be on, turn off

// first, swap VFO's

splitmarker = 1; // use this marker to keep tabs on what the split should be

for( i=0; i<7; i++){/ / s wap VFO's

Serial.print(swapab[i],BYTE); }

for( i=0; i<7; i++){/ / t urn split off for tune routine

Serial.print(splitoff[i],BYTE); }

delay(100); // takes a while for the radio to execute split

// beggiining of the vfo routine


for( i=0; i<8; i++) {

Serial.print (dis[i],BYTE); } //disable tuner


for(int i=0; i<10; i++) {

Serial.print (toff[i],BYTE); }/ / d isable auto tuner feature


for(i=0; i<7; i++) {

Serial.print (ant4[i],BYTE); }/ / a nt 4 select


for(i=0; i<7; i++) {

Serial.print (am[i],BYTE); }/ / A M mode


for(i=0; i<9; i++) {

Serial.print (amlp[i],BYTE); }/ / AM LP


digitalWrite (TUNESTART,LOW); // start the tuner cycle, take TUNESTART pi

digitalWrite (LEDTUNE, HIGH); // Turn on LED during tune cycle

//Serial.println(" tuner started");


digitalWrite (TUNESTART,HIGH); // stop the tuner cycle, take TUNESTART pi



valuekey = digitalRead(KEY);

if (valuekey == HIGH) {

goto keyon;

}/ / w a i t f o r t u n e r t o s t a rt

//start transmission

//Serial.println("tuner says start");

digitalWrite(LEDKEY, HIGH); //Flash the KEY LED

for(i=0; i<8; i++) {

Serial.print (tx[i],BYTE); } //transmit on


value2 = digitalRead(KEY); // wait for cycle to finish

if (value2 == LOW) {

goto keyoff; }

//Serial.println("OK done");

digitalWrite(LEDKEY, LOW); //turn KEY LED off

for( i=0; i<8; i++) {

Serial.print (rx[i],BYTE); } //transmit OFF


for(i=0; i<7; i++) {

Serial.print (cw[i],BYTE); } //back to CW


for(i=0; i<9; i++) {

Serial.print (lp[i],BYTE); } //lp power

//Serial.println("... cycle complete");

//check split marker

if(splitmarker == 0){

goto done; }

for(i=0;i<7;i++) {

Serial.print(spliton[i],BYTE); } // put split back in place


// swap VFO's back

for( i=0; i<7; i++){/ / s wap VFO's

Serial.print(swapab[i],BYTE); }


// Turn off TUNE LED


digitalWrite (LEDTUNE, LOW);

split = 0;


goto listen;