ICOM ID-51 home-made Data cable

Before jumping into the electronics, make sure you have the following tools and parts:

As far as the USB to TTL adapter is concerned, I tested using 2 different ones and both worked just fine. One however was a little more convenient during the debugging phase as it should blink a red led when data was send and blink a green led when data was received. The 2 adapters I used are:

The main motivation for using one or another is how well it will be supported by your OS. I am using MacOS, some adapters require no drivers, some others require drivers but once installed, it works fine. Some USB/TTL adapters also come with a 3.3V/5V switch which can be useful (not in our case), some offers a RX and a TX LED which can be useful for debugging and visualizing whether you are sending/receiving data.

If you run into issues with those adapters, do check your cables first. I have had countless issues using bad/wrong cables such as cables made for charging only…​

Communication with the Radio via cables does require some settings to be set on the radio itself. More on that below but keep that in mind if your radio plays dead …​ I am talking from experience here :)

One of the issue I ran into is an issue that Florian mentioned in his blog post: the 2.5mm jack. I did not expec any issue with that but I was wrong…​ My 2.5mm jack was cute and tiny and I really thought it was a good fit…​ yet it was too big and did not allow proper contact.

It is nearly impossible to check without actually testing the connection so let’s do that first.

We can use CI-V to check that we can receive data from the radio via the data cable. If that test fails, there is no need to go further and the problem needs to be fixed first.

In the ID-51, enable CI-V via data cable in the settings:

We will test in a second but from now on, the radio should be sending CI-V commands via the data cable when you change the frequency for instance. You do not need to transnmit RF for those tests.

First we will test the connection between the radio and the MAX3232. Make sure all the connections are properly soldered and that there is no shorts.

Since the MAX3232 drawws its power from the USB/TTL adapter, make sure you plug this USB/TTL adapter to your computer.

Plug an oscillo or a voltmeter to GND and the cable connected to the RING of the 2.5mm plug. Now, when you change the frequency on the radio, you should see some data coming out of the radio.

If that’s the case, congrats, your connections look good so far.

Notice that we get a RS232 signal from the radio (-5V/+5V). This signal is not TTL (0/+5V). This is an important finding that is confirmed on page 52 of the service manual of the ID-51.

The kudos go to Florian for spotting the J4 connector. The schematics shows the usage of a MAX3221 IC so we know what kind of signal is expected. If you wonder about the voltage limits of the RS232 signal that are acceptable, you may refer to the technical specs of the MAX3221 and you will see that both RIN (±25) and DOUT (±13.2) accept a rather high voltage range.

For this test, the 2.5mm plug does not need to be plugged into the radio. I would even recommend not plugging it so we check what signal we generate before sending it to the radio !

To check whether we are sending data properly, we need to check that: - we do send a TTL signal (0/+~5V) to the MAX3232 - we converts the TTL signal to RS232 (-5V/+5V). We will see that our MAX3232 actually generates a signal that is between -9.80V and +9.80V which is well within the acceptable range of the receiver MAX3221.

This can be done by probing the GND and TX pins of the USB/TTL adapter.

You can use Coolterm on MacOS or some equivalent on Windows. The settings do not matter much so keep it simple with a low Baudrate such as 9600bps for instance. Here are my Cooolterm settings as reference:

Here is the TTL signal generated by the USB/TTL adapter:

As a test, I simply typed the letter 'a' in Coolterm. The TTL signal is a 0/+3.3V signal. This may vary, depending on the USB/TTL adapter you are using.

Now let’s check the signal after conversion to RS232:

We get a signal that is between -9.80V and +9.80V. This is well within the acceptable range of the receiver MAX3221. It is good to see that we are still decoding the letter 'a' :)

This is our final test. Now we need to insert the plug into the radio (make sure the radio still on …​).

In the CS-51 PLUS software, you can now try to read the radio configuration.

It will then show:

You can now try cloning the radio. It will take a few minutes. After cloning your radio, it will reboot.

The following post is about devices that cannot be operated without a proper license. Please make sure you are allowed to use the devices you are building cables for. Check the regulations in your country and make sure you have the proper licenses.

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