[aprssig] Kenwood D710 Mic protocol

[Tom Hayward]

On Thu, Nov 10, 2011 at 07:19, John Gorkos <jgorkos at gmail.com> wrote:
> My thought is to build a simple microcontroller that sits in-line with My
> D710 mic cable.  It could draw off the 8V line on that connector, and have a
> bluetooth transceiver in it and a pic or avr chip that generates the
> appropriate 'serial' protocol to simulate mic keypad presses.  By doing
> that, I could use this handy little wireless, full function keyboard for
> APRS text messaging.  Normal keypad presses would be passed through from the
> mic, but any keypad presses sent over bluetooth would be translated from the
> character sent to the appropriate serial protocol for the mic (including
> multiple presses, if necessary, i.e. you have to hit '2' three times to
> generate a "C".
>
> Anyway, I was wondering if there are any published specs on the protocol
> that the Kenwood mic uses to talk to the D710.  According to the "TM-D710
> Instruction Manual" page 15, pin 8 is "keypad serial data."

You're not the first one to have this idea. This guy has a working
prototype of a keyboard adapter:

http://www.shaneburrell.com/?tag=tm-d710a

It uses an FPGA to generate the mic key signals, because it's a very
odd protocol no one has been able to implement with just a
microcontroller. This page shows what the protocol looks like:

http://www.coastalchip.com/D710.htm

I started a similar project, but to simplify things I planned to
inject serial data on the control head line, because the protocol is a
lot simpler. It's just TTL UART @ 57600 baud (same as many of the
other Kenwood radios). I only got as far as investigating the
protocol, no working prototype.

Tom KD7LXL