Documentation: USB permissions and planner times

Fix permissions on Ubuntu and relative instead of absolute default times
in planner

This contains two changes: One documents the fact that in the planner the
default for time is relative and an absolute time needs an @ sign.

The other hopefully explains how to solve permission problems for USB
devices on Ubuntu: I am told, an USB dongle that pretends to be a serial
port by default does not have the required permissions for the standard
user to write. The transfer then fails with an 'obscure' error message.
The transfer works if subsurface is run by root (which obviously is a bad
idea) or with chmod.  Unfortunately, at least Ubuntu 'fixes' permissions
on reboot. So one either has to fiddle with this (seems to be more
complicated) or add the user to the group 'dialout" which gets write
permissions to serial lines.

This is in theory. I don't have access to an Ubuntu installation to see if
all this is indeed the case. That's why I did not send the patch in the
past. But I think this is still better than what we have so far.

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index f7fad6e0e..765ded59d 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -154,7 +154,9 @@ Now it is time to hook up your dive computer to your PC:
 
 	* On Linux this means you need to have the correct kernel
 	  module loaded. Most distributions will do this automatically
-	  for you.
+	  for you. Make sure you have read/write permissions to that
+	  port. On Ubuntu that could mean you should do 'sudo adduser
+	  [your_username] dialout'.
 
 	* On Windows, the OS should offer to download the correct
 	  driver when you connect your dive computer to the USB port.
@@ -1021,7 +1023,7 @@ are familiar with dive planning or use closed circuit rebreathers.
 | GFlow		| Gradient factor low value affects the ceiling calculation, leave to default if you are not familiar with GF
 | GFhigh		| Gradient factor high value affects the ceiling calculation, leave to default if you are not familiar GF
 | **Ending Depth**	| Depth where current segment ends; a different depth from the previous segment creates a transition segment for ascent or descent, keeping the same depth creates a segment at the given depth. By default the planner uses the measurement for length set in the preferences (meters for most users) - this can be overridden by explicitly specifying 'm' or 'ft'.
-| **Segment Time**	| Enter time in minutes; segment duration / relative time is indicated by a '+':  '+3' or '+3:00' creates a segment that lasts 3 minutes, an absolute time is indicated by @ character. Time '@7:30' means that the segment ends 7 minutes and 30 seconds after the start of a dive.
+| **Segment Time**	| Enter time in minutes; segment duration / relative time can be  indicated by an optional '+':  '+3' or '+3:00' creates a segment that lasts 3 minutes, add an at sign like '@7' for a segment that ends 7 minutes after the start of the dive.
 | **Gas Used**		| Breathing gas mix used; the parser is reasonably flexible and understands terms like AIR, EAN32, 36% or 15/50 (compressed air, 32% nitrox, 36% nitrox or 15% O₂ / 50% He trimix, respectively); leaving this field empty indicates continued use of the previous gas, air by default
 | **CC SetPoint**	| SetPoint when diving with a closed circuit rebreather. Leave empty for open circuit dives with standard scuba equipment
 |===============================================================================