This is a bit of a rant, I must admit, I am mystified by the desire for
USB inside an HF radio. I can understand the need, and value it
myself, of being able to plug in a usb cable to a computer and hook a
radio up to a computer. But requiring the radio to have a noisy USB
chip inside it makes no sense. A cable that goes from the radio to the
computer and has USB on the computer end provides 100% of the
functionality necessary, reduces cost of the radio, and imcreases
options (I.e., I can also control the radi with a microprocessor, or
with an RF data device, both of which interface with serial).
Aside from USB, there are many digital bus standards opewn to amateurs
an uC controller users...even a $1 PIC can handle the Dallas
Semiconductor 1-wire interface, the I^2C interface, and the SPI
interface. (In fact, I would suspect that AUXBUS is either SPI or a
variant.) Though there are PIC chips with USB in them, they are more
expensive, and asymmetric: the host side of the interface, which is what
you need to be able to control a USB radio, is much more burdensome and
generally done only on PC-sized computers.
Others have mentioned ethernet (and Orion and Kenwood have done it),
though the attendant noise is an issue, and Bluetooth RF interface. All
of these could easily be layered on top of one of the 1- to 3-wire
serial interfaces mentioned above, at low cost. And we already know
that Elecraft offers a bump-in-the-cord USB interface already for a low
cost.
As Simon HB9DRV points out, USB may be useful for dumping IF data for a
spectrum analyzer, but I suspect that a baseband signal buffered from
the IF itself would be better than digitizing it inside the K3.
For smaller devices such as HT's, it might be nice to have the standard
camera-sized USB connector some day, but a 4-pin mic jack cable with USB
on the other end would do exactly the same job.
The place USB is useful on other small devices such as my
miniradiosolutions VNA, mostly because it provides power. But even on
those devices, the transfer is still exactly serial, and RS232. The
isochronous transfer mode isn't used, And the power is not very clean:
the SoftRock folks abandoned USB power for just that reason.
Just about every USB device that doesn't use isochronous or bulk data
mode (I.e., except for video cameras, speakers, mics, and disks) is just
a plain old 2-wire serial device. There are a small number of USB chips
from FTDI and others and product designers pick one, pay a royalty and
gett a device id, and then purchase a stock RS232/USB driver which is
bound to that device id. So, on Windows you get Plug-and-Pray, hoping
the manufacturer consents to keep providing their device-locked driver,
when in fact, there is no real driver and all the driver-level
communications is just RS232. As a consumer, you get the power
convenience, and the recognition at plug-in time, but you pay royalty
cost, and you pay in pain at driver install time, and you are out of
luck when the next version of Windows comes out and your manufacturer is
gone.
For cost reasons, the device ID just isn't worth it on the small volumes
we see on ham items.
I can only suspect that the USB marketing board has done too good a
job.
Leigh/WA5ZNU
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