From 720c77615731fbecfce63c727c35762ab7336cad Mon Sep 17 00:00:00 2001 From: "Eric S. Raymond" Date: Wed, 27 Aug 2014 05:12:11 -0400 Subject: Add a caution about use of tag blocks. --- TODO | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'TODO') diff --git a/TODO b/TODO index b3784a49..28d55db1 100644 --- a/TODO +++ b/TODO @@ -52,6 +52,27 @@ Ed W. writes: >really this is just adding it to the NMEA sentence output options via >the TAG structure +However, Iván Sánchez Ortega notes: + +>There is one *big* problem with using TAG blocks to timestamp the sentences. +>The standards (as far as I/we know) say that the timestamp is **either** the +>number of seconds **or** milliseconds since the UNIX epoch, but we do **not** +>know if the initial state should be secs, msecs, or nothing. We do not know +>how clients reading that TAGblocked NMEA stream should ask GPSD to switch the +>timestamp units (or enable/disable them). +> +>There are a few sentences introduced in NMEA 4.00 that supposedly allow that - +>the client sends a sentence to the server, and then the server starts +>TAGblocking sentences. But, alas, there are no examples anywhere. +> +>>From my personal experience, the way to know if a TAGblocked timestamp is in +>seconds or milliseconds is ask the people in charge of setting up the +>device/service. Perhaps some devices output only secs/msecs, and some other +>accept the NMEA 4.00 TAGblock configuration sentences. +> +>I, for one, would like to see the secs/msecs problem solved before GPSD +>embarks on the enterprise of writing TAGblocks. + *** RFC2783 bugs **** detangle TIOCMIWAIT and RFC2783 -- cgit v1.2.1