More on the TH-D72 USB Port
The TH-D72 USB port is configured as a CDC device, using the CP2102 USB UART bridge. On Windows, presumably you should use the drivers provided by Kenwood. I accessed the port on my Ubunutu 10.04 desktop just by using /dev/tty.USB0, which popped open when I connected the device. CP2102 support evidently is built into recent kernels. Looking around, it seems that MacOS support is more dicey, so I'll probably experiment with it using a linux box or a virtual linux machine on my MacBook. For the person like me, who is hoping to connect this to an embedded device, there's some particularly bad news: this chip doesn't communicate using the plain CDC-ACM; I'm told it has a proprietary communication system to the host. The best bet is to port the software from the linux kernel, alas.