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author | Eric S. Raymond <esr@thyrsus.com> | 2010-03-28 13:32:34 -0400 |
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committer | Eric S. Raymond <esr@thyrsus.com> | 2010-03-28 13:32:34 -0400 |
commit | a6f96f95f9f8cbd183cb1910f7627a0493bb087d (patch) | |
tree | 87a7689990e5fbe9fa83af042aeba95f1afb1844 /www | |
parent | 90365bc8ec17a1674a51409d1037f35a68b00f1c (diff) | |
download | gpsd-a6f96f95f9f8cbd183cb1910f7627a0493bb087d.tar.gz |
Typo fix and a bit of new information.
Diffstat (limited to 'www')
-rw-r--r-- | www/faq.html | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/www/faq.html b/www/faq.html index dcee3c0f..0c53a5af 100644 --- a/www/faq.html +++ b/www/faq.html @@ -525,14 +525,17 @@ observing something like a 1 ms high sawtooth in the time-reports.</p> <p>For accurate time reference, use a PPS line over RS232 triggering an interrupt. Serial bus interrupt latencies on modern hardware on the -order of 10 microseconds, roughly a hundred-fold impovement over +order of 10 microseconds, roughly a hundred-fold improvement over USB.</p> -<p>Don't confuse PPS with conventianal, non-PPS data transport over RS232; -the latency on that is much higher. At one character per ten bits -(counting framing at stopbits) a 9600-bps serial link introduces -about a millisecond of latency <em>per character</em>; both USB and -RS232 will incur that overhead.</p> +<p>Don't confuse PPS with conventional, non-PPS data transport over +RS232; the latency on that is much higher. At one character per ten +bits (counting framing at stopbits) a 9600-bps serial link introduces +about a millisecond of latency <em>per character</em>; furthermore, +the Linux kernel will normally delay delivery of characters to your +application until the next timer tick, about every 4 milliseconds in +modern kernels. Both USB and RS232 will incur that approximately +5ms-per-char latency overhead.</p> <h1 id='sleep'>Why does my GPS get lost when I sleep/wake my laptop?</h1> |