Doug Sutherland wrote:
Josh wrote:
I have always thought of HID as using an external device that then
communicates to the computer, this is using a virtual app on the
computer to control an external device - I don't disagree that it is
Human Interface.
Aside from keyboards and mice, this idea is exactly what generic
HID is for. I have seen others that do the same. For example
audio codec evaluation boards use generic HID communication
and have volume, balance, fader etc controls in a similar PC app.
Interestingly though, generic USB HID can also be used as just a
simple comminication protocol between host and slave, and can
do pretty decent throughput.
ok, cool - thanks for the explanation.
I will look further into this, because I have some of the SI4701
chips here too, my intention was to write my own SPI code on
a different micro, so I haven't looked too closely at their source.
I was thinking about doing something better: using a micro to
create a virtual com port, using the driverless USB ACM CDC
(communication device class), which would be translated to the
necessary SPI commands on the micro firmware, to control
the FM tuner and to read and send the RDS/RBDS data.
This way you would have generic USB audio and generic
USB CDC serial, and you could just open a serial port and
send commands to change stations and such, and the RDS
data would just "arrive" at the serial port.
This assume a different custom small board with SI4701 and
microcontroller, most likely an ARM7.
wow - that sounds like a pretty cool approach. Not having those
engineering skills :) I was looking to more COTS products. I may pick
up one of the dongles to just see if I can hack something out with my
utter lack of C++ expertise.
Please keep the list posted on your progress and let me know if I can be
of any help.
One of the apparent weaknesses of the Si USB dongles (from my armchair
research) is the antenna connection - it might be nice to have a mini
SMA or something (with the standard FM resistance -- 75 Ohms?) that
would be robust and an adpater cable could be used to car antenna or
such - of course, in an embedded device, the old 'headphones as antenna
works well enough, but since this would external anyway, it might make
more sense to allow for a 'real' antenna.
j.
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