From 4698884efb9338d43b6bb39b8c5622b72abbca21 Mon Sep 17 00:00:00 2001 From: Siraaj Khandkar Date: Sun, 11 Oct 2015 17:13:05 -0400 Subject: [PATCH] Describe packet structure in README --- README.md | 40 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index 91089e6..83fc683 100644 --- a/README.md +++ b/README.md @@ -101,8 +101,44 @@ a filter), so you'll have to access their raw version, if needed. } = lists:keyfind(pitch_roll_heading, 1, GroupsNamed), ``` -Data format references ----------------------- +Packet structure +---------------- +```erlang +<<"DATA", PacketIndex:8/integer, Groups/binary>>, +<< GroupIndex:32/little-integer + , GroupValue1:32/little-float + , GroupValue2:32/little-float + , GroupValue3:32/little-float + , GroupValue4:32/little-float + , GroupValue5:32/little-float + , GroupValue6:32/little-float + , GroupValue7:32/little-float + , GroupValue8:32/little-float + , GroupsRest/binary +>> = Groups, +``` + +Where `PacketIndex` indicates something like a schema version, i.e. what each +of the numbered groups means. For example, in X-Plane 10, packet index is 64 +(character `"@"`) and group 3 contains speed data, in which the 8 group values +are: + +| Location | Label | Description | +|----------|---------------|-------------| +| 1 | `vind_kias` | Velocity indicated, in knots indicated airspeed. | +| 2 | `vind_keas` | Velocity indicated, in knots equivalent airspeed (the calibrated airspeed corrected for adiabatic compressible flow at the craft's current altitude). | +| 3 | `vtrue_ktas` | Velocity true (the speed of the craft relative to undisturbed air), in knots true airspeed. | +| 4 | `vtrue_ktgs` | Velocity true, in knots true ground speed. | +| 5 | | Unused. Contains a dummy value. | +| 6 | `vind_mph` | Velocity indicated, in miles per hour. | +| 7 | `vtrue_mphas` | Velocity true, in miles per hour airspeed. | +| 8 | `vtrue_mphgs` | Velocity true, in miles per hour ground speed. | + + +References +---------- + +- `X-Plane_10_manual.pdf` (distributed with X-Plane 10) - http://b58.svglobe.com/data.html - http://www.nuclearprojects.com/xplane/xplaneref.html -- 2.20.1