Yaesu VX-8DR Serial Interface

Here is some of what I've learned about the Yaesu VX-8DR radio, it's serial interface and the programming software that is available for it.   One of these days, I'll get my notes off of my private wiki and move them into a public wiki.   I'm posting this to help others until I get around to it.

The VX-8DR has a serial interface available in the proprietary microphone connector that is used for backing up and restoring the radio's configuration and for talking to a GPS.   The backup/restore feature is referred to by Yaesu as cloning, since their purpose is it being used to program one radio and then clone it's configuration to other radios

Build your own cable

A custom cable is needed to use the radio's serial interface for two reasons.  First, the connector is a Yaesu proprietary design that is intended to be water proof.   Second, as is typical with embedded and battery systems the serial interface isn't at RS-232 voltage levels but is at 3.3V. It's possible to build your own cable if you obtain the Yaesu connector.  The Yaesu CT-M11 external speaker/microphone cable provides the proprietary connector on one end and bare leads on the other end.    The pin-out of the cable and the wire color coding is actually in the VX-8DR owner's manual.  Unfortunately the cost of the bare cable is close to what you'd expect to spend on a complete data cable.

If you want to connect the radio to a standard RS-232 port, a level converter is needed to convert the  0 - +3.3 volts used by the radio to the levels used by RS-232 which are supposed to be on the order of -12Vdc to +12Vdc.  I believe the RS-232 spec calls for something between 10-15 volts.  Note the polarity, negative voltage for the low, or zero equivalent, positive voltage for the high, or one equivalent signal.   Note: the peak to peak voltage swing could be 20 to 30 volts.   This isn't very convenient in modern, low voltage, battery powered devices.   The serial ports on laptops (when they still had serial ports) were often closer to -5 V to +5 V.   Level converters such as the max232 have been used for many years to turn RS-232 voltage levels into TTL (0-5V).   There are many level converter schematics that have been published.  They can be something as simple as some zener diodes, a switching transistor and some resistors, or can use modern versions of the max232 like the max3232, which has a significantly reduced parts count.  There is also 3.3V available on the microphone connector which is used for powering the GPS that could be used to power the max3232.

To connect to a computer via USB as a serial device, an FTDI USB to serial bridge can be used directly without a level converter.  FTDI makes a number of cables that can be connected directly.  If you want to limit the number of FTDI cables you need to buy, the FTDI TTL-232R-3V3 provides a 6 pin header connector. I have one of these for connecting to XBees, the Adafruit Boardurino, etc. The 6 pin header connector is found on many of the less expensive Arduino clones that don't have their own FTDI USB->serial chip on board.   This can also be useful to have for talking to the 3.3V serial console of many embedded sysstems like the Linksys WRT54g wireless router.   Note: while this 6 pin header connector has become a little bit of a defacto standard, it has it's drawbacks.  First, it's not a polarized connector so you need to be careful not to plug it in backwards.  Second, it doesn't contain a full set of control signals, just RTS & CTS.   If you need DTR you are out of luck with this cable.

VX-8 Connection Pinout

Pin No.	CT-M11 Wire Color	VX-8 Description
1	Orange	Microphone and Push to talk
2	Gray	+3.3Vdc
3	Brown	Speaker OUT
4	Green	GPS TXD (CONTROL)
5	Blue	GPS RXD (NMEA)
6	Red	Ground
7	Black	Internal speaker disable

More Details:

• Yahoo VX-8 Group - Has a number of schematics available in the files section.
• FTBVX8 Programming Software - The help/manual has extensive info on VX-8 cables.  They also have a cables page which info that applies to many radios.
• decafbad.org  VX-8 data pin out blog post Also useful about the Yaesu GPS.
• Worldwide DX forum thread on pin out and GPS

Buy a USB data cable

RT Systems

To just buy a cable, RT Systems sells one with their VX-8DR programming software, ADSM-VX8. The cable has an FTDI chip in it. However, they have changed the USB Vendor and Product ID (VID & PID). Since the IDs are different the operating system won't recognize the FTDI chip and assign the common FTDI virtual serial port driver. In order words, under windows it won't show up as a COM port. To use that cable with your own software requires either using the FTDI direct I/O library or tricking the OS into mapping that VID/PID into the FTDI serial driver. I'll post the instructions for the later under Linux in a separate entry.   It should also be possible to use the FTDI utilities to change the settings on the chip and change the VID/PID back to the FTDI serial defaults.  However, the problem is the RT Systems software will only work with their cable.  This is one of my primary reasons for recommending G4HFQ's FTBVX8 software over RT Systems ADMS-VX8.   (Note: I'm sure not supporting home made cables makes RT Systems life a lot easier, but given the market, hams are all about DIY.)

Radio Arena

In the UK, Radio Arena makes an alternative cable that also has the audio connections for doing data modes with your computer via the sound card.  This uses your sound card as a modem and doesn't use the VX-8's built-in TNC.   It has the isolation transformers on the audio lines that should help keep noise from crossing over between the computer and the radio.

One reservation I have about this cable is the use of the Prolific USB serial bridge.   Early on there were some stability / reliability problems with the Prolific chips.  Many of the devices I came across recommended only using FTDI because they were very reliable and stable.  FTDI is a staple of embedded systems and microcontroller work. The bad reputation that the Prolific chip and/or it's drivers had may be in the past.  FTDI serial bridge chips are not inexpensive.  I've paid the premium for FTDI to give me the least amount of headaches.  Still given they sell this cable for 25 GBP, or currently $37.50 USD, it's attractively priced.  The Yaesu CT-M11 cable is approximately $25 USB by itself.

Ebay

There are various sellers of VX-8 data cables on Ebay. Most of which are selling cables made in China using the Prolific chip. The pricing to me doesn't seem to be that much of a bargain.  There still seem to be a lot of links to Prolific's site in Taiwan to get the latest drivers.

I hope this collected info helps someone else.  It sure would be nice if there were some good ham wiki resources.