VX-8 data cable
by trixter on Sep.16, 2009, under Yaesu VX-8r
I finally got my CT-M11 cable today, and started trying to build a data cable for it. I discovered that cloning does indeed go over the RS-232 data pins. This means that I will be writing a tool to load the memory the way that RT systems does it (although I will give the software away for free 
Additionally I pulled out the multimeter and decided to try to map the 5 pins the GPS uses. It appears that one of the 5 is never used, without pulling apart the GPS I will not be able to easily see why it is even there. It *might* be used if you have the hand mic that takes the GPS, as I do not have one of those I cannot say for sure.
The pinout of the connector is as follows:
This is as you are looking at the radio, and not as you are looking at the cable.
Pins 1, 3, 7 are not connected through the CM-136 GPS adapter.
If you look at the top of the GPS adapter, without the GPS module installed, you will see two rows of 7 contacts. If you hold it so that what goes on the backside of the radio is on top you will see something simialr to this:
1 2 3 4 5 6 7 8 9 10 11 12 13 14On the top row (back side of the radio):
5 – 3.3v
6 – GPS Rxd
7 – GNDOn the bottom row (front side of the radio):
13 – GPS Txd
14 – not connected although there is a pin from the GPS for here
I think that if you wanted to just do serial, making a small board that fits in there would not be difficult, or you could wire up a CM-T11 cable just as easily.
I should have my CM-T11 cable working in the near future, it will let me connect it to a TNC, do cloning, and experiment to see if there are hidden commands. I think it is incredibly silly that Yaesu did not give you the capability to control the TNC built in via serial.
Thinking about this logically, the radio is an embedded computer. It runs software, that software can talk to the TNC and has an APRS stack built in. That software can also talk to the serial port, for cloning, to poll the GPS, etc. It would not be that difficult to have it read data from the serial port and either relay it bit for bit or have some special protocol that lets you send data using the integrated APRS/X.25 stack.
For all I know there are undocumented commands to tell the radio to send data out the TNC, I know Yaesu claims there are not, but that just means they do not want to support that feature, not that it doesnot exist.
October 9th, 2009 on 2:21 pm
Near as I’ve heard the radio actually does not have a TNC built in, the speakermike does… Thus there is no tnc if you connect the radio directly to your computer.
October 9th, 2009 on 4:07 pm
To be absolutely clear, the TNC is in the radio, the speaker mic is just that, along with a pass through of the 3.3v, ground and serial pins for the gps module which may optionally sit on top of the speaker mic. Anyone who claims the TNC is in the speaker mic is wrong.
If you do not believe me, and why should you, go to a ham store and ask to see a VX8. Make sure the gps and speaker mic are not connected. Turn it on, set VFO-B to 144.39, turn APRS on (1200bps will probably be best). If there is APRS acitivity in your area you will be able to see it in the APRS menus. This will let you confirm for yourself where the TNC is and not just take my word for it, and it will let you feel confident in no longer spreading false rumors. You will have to enter a callsign for the APRS stuff to work (although I think it has a default one … that is bad m’kay?) you may have to manually enter some GPS coordinates (it caches the last GPS data it got, if it never had any it will probably be all zeros and it may require some change from that location although technically that is a valid location).
For the record I do not have the speaker mic, I do have the gps, but APRS works without that (obviously you have to manually enter your coordinates). I am able to send and receive messages between my laptop running xastir and my VX8 (using a separate radio of course). I am able to read everyone elses traffic as well.
I do not know who started that rumor, I have seen it too, and the people that were saying it largely were saying it before the device was available. One person claimed to have a pre-release version of it who claimed it was in the speaker mic, and I question if they ever had a pre-release version because it seems unlikely that Yaesu would make a speaker mic with a TNC then take it out and put it in the VX8 just before release. Hardware changes like that cause massive production delays.
October 29th, 2009 on 7:46 am
Do you have a VX-8r memory dump you would be willing to share? I have not been able to get the radio and would like to test some software I am working on?
October 29th, 2009 on 10:41 am
no, I have been distracted and have not played with this radio much lately. I do not know if doing a memory dump is possible, that was one of the things that I wanted to play with and see. Other than serial for cloning and sending gps coordinates I do not know what is available via the serial port.
February 11th, 2010 on 7:01 pm
Any more progress on this? I’m strongly considering getting one of these, but I’d really like to be able to use the TNC.
February 12th, 2010 on 12:58 am
no progress, I have been busy with other things. I am not even certain that you will ever get access to the internal TNC, and for all I know its just a software DSP based one which means that something like soundmodem would work the same. If the software is written only for aprs then it may be that you never have access to the raw data and it would only support one mode, unless of course someone could get access to that code and write in some additional hooks to get the data.
I just dont know at this time.
August 2nd, 2010 on 7:59 pm
In light of Yaesu’s upgrade program being offered for the VX-8R to VX-8DR, I would suspect that the ‘TNC’ is only implemented in software. I have not sent mine in to be upgraded yet, but others I know have already received their radio back, and there seems to be no physical alterations (as far as I can detect) internally or externally. Still, it’s a shame there isn’t an easy way to tap into it.
August 11th, 2010 on 7:29 pm
according to Yaesu there are discrete component changes that are required to upgrade the Vx8. With that said I personally think its just firmware that is changed, which is contained at least in part on the cpu itself. They do not want the firmware out for fear of people modding in ways that violate FCC rules. In 1994 Yaesu almost lost their FCC approval for the FT-50 because it was easily modded to “freeband” which was a real freeband, it would Tx anywhere the hardware locked. Their solution was a firmware change in newer radios where the bandplan data is all the same for US models. They do not want a repeat of this, there is too much money at stake, so they make it sound mysterious to upgrade it.