Re: [gpsd-dev] PPS over USB

[Ed W]

On 07/05/2012 04:20, Eric S. Raymond wrote:
> Hal Murray<address@hidden>:
> > Is there a list of serial-USB chips that are known to work and/or not work?
> You can generate one by grepping for TIOCMIWAIT in the driver tree.  Gary
> did this as one point.  The PL2303 is defintely good, the CP210x bad.

Apart from PPS signals, does TIOCMIWAIT improve gpsd accuracy in any 
other way?  Phrased another way are CP210x any worse than a generic 
PL2303 device?

I couldn't get a definite opinion, but CP210x devices appear to be USB2? 
I currently see around 1ms jitter on my device using just the NMEA clock 
- perhaps I ought to be expecting lower than this?

I think TIOCMIWAIT could be added to the driver. However, does this buy 
me anything on generic non PPS devices?  Any other changes which would 
improve precision of the NMEA date?


Big picture question - Am I going to get better accuracy using your new 
device than I am from these CP210x Venux6 devices?


Thanks

Ed W