Greg KH <greg@xxxxxxxxx>: > Based on the source you sent me, it's been included in the kernel since > before 2.6.29 (2.6.29 is when some bug fixes went in for the card), so > any "modern" Linux distro should support it just fine. Excellent. With TIOCMIWAIT working? > The hub isn't the issue, it's the UART controller in the USB device that > is the issue. Some of them don't do DCD at all, just data. It depends > on that controller if it will work with your application or not. That makes sense. OK, for your information most GPSes (including my design) use a PL2303. That TIOCMIWAITs just fine. Your odd piece of serial-device trivia for the day: Almost all GPS modules export 1PPS that is a top-of-UTC-second notification accurate to 50ns...but in most consumer-grade GPS hardware it's only used to light the LED! This is like using an F-16 to deliver newspapers. There's a bog-standard design for cheap GPS pucks where you slap the GPS chip and a PL2303 on a micro-PCB, then tie the TTL-level RS232 TX/RX lines from the GPS to the TX/RX on the inboard side of the PL2303, then run the GPS's DCD line through a pulse spreader to the LED. What I did was notice that if you take the DCD line on the GPS chip and tie it to DCD on the PL2303, the PL2303 obligingly latches 1PPS and ships it as an emulated DCD event at the next poll. Voila! 1PPS accurate to 1ms - you lose a factor of 200 accuracy but it's still more than good enough to run a Stratum 1 NTP server. For cheap, like $30 a unit. Now if I could just find a U.S. distributor who's willing to carry them... -- <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a> -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
