NX-3300 Trying to build DIY programming/accessory cable

[LynxVortex]

Hi guys, I recently got a Kenwood NX-3300, and I’m working on a small personal project. I also have NX-800 and NX-820 radios, and I’m trying to build a custom cable/system to link them together and make them behave like a small network. The radio(nx-3300) programs are perfectly fine with the original KPG-36X cable, so I know the radio itself is okay
Now I’m trying to access the radio through the accessory connector directly, using jumper wires (TXD, RXD, GND) and a CP2102 USB-TTL adapter, but I get absolutely no communication. What makes it even more confusing is that I’m seeing weird voltage levels on the pins

TXD pin sits at about 5.49 V
RXD pin sits at about 3.19 V

So this clearly doesn’t look like a simple 3.3 V TTL UART. This makes me think that the KPG-36X cable is not just a basic USB-TTL cable, and that there is some extra electronics or some kind of enable/handshake going on. I’m not looking for software, I’m just trying to understand the hardware interface.
My questions:

Does anyone know what’s actually inside the KPG-36X? (I found one on the Internet, figure 8 in the photos. It looked like a simple UART and USB converter circuit to me.)
Is there some extra pin or signal needed to put the radio into programming/accessory mode?
Has anyone here ever built a DIY KPG-36X?
If yes, what was the trick that made it work?
Also, I’ve seen some third-party cables that seem to only use 3 pins and just a USB cable. How do those work?
Any info, measurements, or experience would be really appreciated. Thanks!

 

[kd4efm]

Mobile relay is only available on the nx5000 mobile. Best not to use the portable like that, and be careful, you could blow the usb chip and that's not warranty repairs if that happens.

The use of the TXD RXD like that is not like you think. Hence why mobile relay is only in the nx5000, and not the 3000.

 

[LynxVortex]

Mobile relay is only available on the nx5000 mobile. Best not to use the portable like that, and be careful, you could blow the usb chip and that's not warranty repairs if that happens.

The use of the TXD RXD like that is not like you think. Hence why mobile relay is only in the nx5000, and not the 3000.

Thanks! And I understand the warning.
I think there’s a small misunderstanding about what I’m trying to do.
I’m not trying to use the NX-3300 as a relay feature. I’m simply sending data to the radio and reading data back. This already works in my tests when I use the KPG-36X cable.
Now I just want to make my own cable that behaves the same way.
With the original cable, the PC detects it and the radio starts receiving commands. With a direct CP2102 USB-TTL connection to TXD/RXD/GND, nothing happens.
So it looks like the KPG-36X is doing more than just USB-to-UART.
Do you know what extra signal or condition is needed to make the radio enter that mode?

 

[AM909]

Maybe counterfeit/bad CP2102 or driver problem? Miklor is a good resource:

Cables & Drivers - Prolific & FTDI

Cables & Drivers - Prolific & FTDI

www.miklor.com

 

[kd4efm]

Thanks! And I understand the warning.
I think there’s a small misunderstanding about what I’m trying to do.
I’m not trying to use the NX-3300 as a relay feature. I’m simply sending data to the radio and reading data back. This already works in my tests when I use the KPG-36X cable.
Now I just want to make my own cable that behaves the same way.
With the original cable, the PC detects it and the radio starts receiving commands. With a direct CP2102 USB-TTL connection to TXD/RXD/GND, nothing happens.
So it looks like the KPG-36X is doing more than just USB-to-UART.
Do you know what extra signal or condition is needed to make the radio enter that mode?

I cannot share the document because it is marked CONFIDENTAL

Now that being said, I can walk you through what I DO when I am using D-RATS and Transparent Mode. NXDN Data mode to send files and text messages.

The kenwood NX line is capable of data send and receive like you mention, but you did not tell me you trying to do it voice/data, or just data.

Now, using my radio for demonstration, and not the actual document, tell me this is what you are doing.






FROM THE HELP FILE:




The other question I have, is why not Bluetooth IF you have BTSPP installed? (must have this option in order for it to work)

So, with this training aid, I can only opinionate the functions with what you are trying to accomplish with out divulging who this is for or other Intellectual Properties you may have in place.
I can only guide you along as a mentor to better your communications technician field experience.

 

[kd4efm]

Now, I probably went way off in left field, but that's okay.
I take it you're trying to reinvent the wheel of programming cables and make something like BLUEMAX49ERS cable for your self.

The NX3k and 5K are USB Native, just like the Viking series.
Have you tried just making the connection via USB rather than constructing another cable?

By the way, the KPG-236UM is USB native OEM cable the works with the NX-3k, 5k, VP-x000 radios.

 

[AM909]

The NX3k and 5K are USB Native, just like the Viking series.
Have you tried just making the connection via USB rather than constructing another cable?

This here is probably the answer. For example, for use with the NX-5k mobiles, I built a simple backup for my KPG-46 by changing the "B" end of a regular USB A-B cable to an RJ45. No level or protocol translation required.

 

[LynxVortex]

Now, I probably went way off in left field, but that's okay.
I take it you're trying to reinvent the wheel of programming cables and make something like BLUEMAX49ERS cable for your self.

The NX3k and 5K are USB Native, just like the Viking series.
Have you tried just making the connection via USB rather than constructing another cable?

By the way, the KPG-236UM is USB native OEM cable the works with the NX-3k, 5k, VP-x000 radios.

Sorry for the late reply.
I checked a few documents, and what you said makes sense. The data part probably shows as None because I only have the radio itself. I couldn’t get the KPG-D3 yet.
I’m not trying to do anything fancy; I just want basic data transfer (J-Commands)
I haven’t tried a direct USB connection yet, but I’ll test that next and report back with the results.
Thanks for the clarification about the case