[Thumbgps-devel] Bad news on the UD731

[esr@thyrsus.com (Eric S. Raymond)]

Tested.  Works fine as a GPS, and I've added it to the GPSD hardware
page with an "Excellent" rating.

Unfortunately, I can't see 1PPS from it.  Investigation reveals that
the Linux support for the CP2101 Serial-to-USB adapter is weak and
does not implement the TIOCMIWAIT call required to make a thread wait
on a handshake-line change.

Further investigation suggests that this is the vendor's doing.  To
meet its obligations under the GPL SiLabs released heavily obfuscated
source code.  That code had to be reverse-engineered without the
company's help in 2005. A 2006 promise by the company to supply
unobfuscated driver source was not fulfilled.  Now the company has
declared the chip obsolete and the programming guide for it is no
longer available from the SiLabs website.

I have sent email to the Liux driver maintainer asking if there is any
chance TIOCMIWAIT can be made to work, but I'm not expecting a happy
answer.  The Linux crew has done just about everything it can in a
case like this; the vendor has repeatedly and obstinately refused to
divulge the technical information required for full support of the chip.

I don't think we can use this adapter, and given the vendor's
bad attitude I wouldn't want to steer them more business even 
if we could fix the driver.

Ms. Liu, does UniTraq have any designs using a PL2303 we could modify?
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>

"America is at that awkward stage.  It's too late to work within the system,
but too early to shoot the bastards."	-- Claire Wolfe