.\" @(#)$Id: xoscope.1,v 2.5 2009/08/14 03:15:06 baccala Exp $
.\"
.\" Copyright (C) 1996 - 2000 Tim Witham <twitham@quiknet.com>
.\"
.\" (see the files README and COPYING for more details)

.TH XOSCOPE 1 "May  6  2001" "Linux" "User Commands"
.SH NAME
xoscope \- Digital Oscilloscope
.SH SYNOPSIS
xoscope [X toolkit options] [xoscope options] [file]

.SH DESCRIPTION

.B Xoscope
is a digital real-time oscilloscope. It graphically displays signal
amplitude or bit logic as a function of time.  Signals may be
displayed, saved, recalled, and manipulated by math functions.  Signal
input devices currently include:
.P

.TP 0.5i
.B Soundcard
Audio sound recording via Advanced Linux Sound Architecture (ALSA).
Two 8-bit analog channels at 8000 S/s to 44100 S/s.  Left and right
audio is connected to A and B inputs respectively.  Use an external
mixer program to select which sound inputs to record.  AC coupled,
voltages unknown, 256K sample memory.

.TP 0.5i
.B EsounD
Shared audio sound via the Enlightened Sound Daemon.  This is great
for watching music but support for it is an option at compile-time.
EsounD is auto-detected and preferred over /dev/dsp.

.TP 0.5i
.B COMEDI
The COMEDI project (www.comedi.org) develops Linux drivers, tools, and
libraries for data acquisition.
Many commercially available ADC cards are supported by COMEDI, and
.B Xoscope
can receive signals from them via the COMEDI library.

.PP
.SH "RUN\-TIME KEYBOARD CONTROLS"

.B Xoscope
is an interactive program and can be completely controlled from the
keyboard at run-time.  In verbose key help mode, each available key is
shown on the screen in (parentheses).  The following single key
commands are available:

.TP 0.5i
.B ?
Toggle verbose key help display mode.

.TP 0.5i
.B Escape
Immediately quit the program.

.TP 0.5i
.B @
Load a previously saved file.  You are prompted for the filename.

.TP 0.5i
.B #
Save current settings and memory buffers to a file that can be loaded
later.  You are prompted for the filename and asked for confirmation
to overwrite if it already exists.

.TP 0.5i
.B Enter
Clear and refresh the entire screen.

.TP 0.5i
.B &
Cycle between the various input devices.  Note that this key will not
toggle to an unresponsive input device, so if only one device is
present, it will appear to have no effect.

.TP 0.5i
.B *
Different behavior for different input devices

Under EsounD, this value instead determines whether the connection to
EsounD will block or not.  Blocking mode is nicest to CPU
usage but the
.B xoscope
interface will not respond when the there is no sound stream coming
from EsounD.  Nonblocking mode will let
.B xoscope
be responsive whether sound is available or not, but will consume all
available CPU cycles.

Under COMEDI, this key toggles between different analog reference
points (ground, differential, or common).

.TP 0.5i
.B ^
Different behavior for different input devices

.TP 0.5i
.B (/)
Decrease/increase the sampling rate.

.TP 0.5i
.B 9/0
Increase/decrease the Sec/Div horizontal time scale (zoom out/in on
time).

.TP 0.5i
.B -/=
Decrease/increase the trigger level.

.TP 0.5i
.B _
Cycle the trigger channel.

.TP 0.5i
.B +
Cycle the trigger type: none, rising edge, or falling edge.

.TP 0.5i
.B Space
Cycle the trigger mode: run, wait, stop.  Run mode
continuously acquires and displays samples after trigger events.  Wait
mode waits for the first trigger event and displays only the first set
of samples; this is "single-shot" mode.  Stop mode suspends the data
acquisition and displays the current samples.

.TP 0.5i
.B !
Cycle the plotting mode: point, point accumulate, line, or line
accumulate.  In the accumulate modes, all samples stay on the screen;
use
.B Enter
to clear them.

.TP 0.5i
.B ,
Cycle the graticule style: none, minor divisions only, or minor and
major divisions.

.TP 0.5i
.B .
Toggle the graticule position: behind or in front of the signals.

.TP 0.5i
.B '
Toggle the manual cursors on/off.  When manual cursors are displayed,
the measurements between the cursor positions are shown.  When cursors
are not displayed, automatic measurements are shown.

.TP 0.5i
.B """
Reset both manual cursor positions to the sample just after trigger.
.\" "

.TP 0.5i
.B Ctrl-q/w/e/r
The Control key held down in combination with q/w/e/r moves the first
cursor back or forward by 10 samples or back or forward by 1 sample
respectively.

.TP 0.5i
.B Ctrl-a/s/d/f
The Control key held down in combination with a/s/d/f moves the second
cursor back or forward by 10 samples or back or forward by 1 sample
respectively.

.TP 0.5i
.B 1\-8
Select the corresponding display channel.  Measurements are displayed
for the channel.  Channel 1 and 2 are used as input to the math
functions so they can't be used to do math.  By default, they are
connected to the A and B input channels.  Channel 1 and 2 can also be
used to display memory buffers or for doing math on memory
or the alternate input.  Channel 3 through 8 are not restricted and
can be used for any purpose.
The remaining single key commands operate on the currently
selected channel:

.TP 0.5i
.B Tab
Toggle visibility: Hide or show the selected channel.

.TP 0.5i
.B {/}
Decrease/Increase vertical scale of the selected channel.

.TP 0.5i
.B [/]
Decrease/Increase vertical position of the selected channel.

.TP 0.5i
.B `/~
Decrease/Increase number of logic analyzer bits displayed.  The
default of zero bits plots the signal as one analog line of varying
amplitude.  Any other value plots multiple digital lines representing
the least significant bits from bottom to top.

.TP 0.5i
.B ;/:
Increase/Decrease the math function of the selected channel.  This is
not available on channel 1 & 2.

.TP 0.5i
.B $
Show the result of an external math command on the selected channel.
You are prompted for the command.  The command must accept samples of
channel 1 & 2 on stdin and write a new signal to stdout.  See operl,
offt.c and xy.c in the distribution for examples of external math
filter commands.  Not available on channel 1 & 2.

.TP 0.5i
.B a-z
Recall the corresponding memory buffer or input device to the
currently selected channel.  Input device channels are mapped
to the earliest letters of the alphabet; the
rest of the buffers are available for signal memory.

.TP 0.5i
.B A-Z
Store the currently selected channel into the corresponding memory
buffer.  Early letters of the alphabet can not be used because they're
reserved as the signal inputs, so the exact number of available buffers
is dependent on the input device.  Memories are stored from time zero to
the current display update position.  So it is best to STOP the
display before storing to a memory buffer.

.PP
.SH "MOUSE CONTROLS"
.B Xoscope
adds mouse controls to menus or around the edges of the scope area.
These should be nearly self-explanatory.  They perform the same
functions as the equivalent keyboard commands above.  If built with
GTK+, a context-sensitive pop-up menu is available with right-click to
select channels, change scale and position, recall and store signals
and so on.  Left click decreases a variable while right click
increases.  The manual measurement cursors can also be positioned with
the mouse.

.PP
.SH "COMMAND\-LINE OPTIONS"

The command-line options define the startup state of
.B xoscope
and have reasonable defaults.  All options may be capitalized in case
they conflict with an X toolkit option.  These options are also
recorded in text files saved by
.B xoscope.

.TP 0.5i
.B -h
Help usage message showing these startup options with their default
values, then exit.

.TP 0.5i
.B -# <code>
Startup conditions of each channel.  # is a channel number from 1 to
8.  Code can have up to three fields, separated by colons:
position[.bits][:scale[:function #, memory letter, or external
command]].  Position is the number of pixels above (positive) or below
(negative) the center of the display.  Bits is the number of logic
analyzer bits to display.  Scale is a valid scaling factor from 1/50
to 50, expressed as a fraction.  The third field may contain a
built-in math function number, memory letter, or external math command
to run on the channel.  Using these options makes the channel visible
unless position begins with a '+', in which case the channel is
hidden.

.TP 0.5i
.B -a <channel>
Active, or selected, channel.

.TP 0.5i
.B -r <rate>
Sampling Rate in samples per second.  For the sound card, current valid values
are 8000, 11025, 22050, or 44100.

.TP 0.5i
.B -s <scale>
Time Scale factor from 1/500000 to 2000 (2 ns/div - 2 s/div) 
expressed as a fraction where 1/1 is 1 ms/div.

.TP 0.5i
.B -t <trigger>
Trigger conditions.  Trigger can have up to three fields,
separated by colons: position[:type[:channel]].  Position is the
number of pixels above (positive) or below (negative) the center of
the display.  Type is a number indicating the kind of trigger, 0 =
automatic, 1 = rising edge, 2 = falling edge.  Channel should be x or
y.

.TP 0.5i
.B -l <cursors>
Manual cursor Line positions.  Cursors can have up to three fields,
separated by colons: first[:second[:on?]].  First is the sample
position of the first cursor.  Second is the sample position of the
second cursor.  The final field is weather the manual cursors are
displayed (1) or the not displayed (0).

.TP 0.5i
.B -p <type>
Plot type.  0 = point, 1 = point accumulate, 2 = line, 3 = line
accumulate, 4 = step, 5 = step accumulate.

.TP 0.5i
.B -g <style>
Graticule style.  0 = none, 1 = minor divisions only, 2 = minor and
major divisions.

.TP 0.5i
.B -b
Whether the graticule is drawn Behind or in front of the signals.

.TP 0.5i
.B -v
Whether the Verbose key help is displayed.

.TP 0.5i
.B file
The name of a file to load upon startup.  This should be a file
previously saved by
.B xoscope.

.SH EXAMPLES
.TP 0.5i
.B xoscope -1 80 -2 -80 -3 0:1/5:6 -4 -160:1/5:7

This runs
.B xoscope
with channel 1 above and channel 2 below the center of the display.
Also channel 3 and 4 are made visible to show the FFT of channel 1 and
2 respectively at a reduced scale of 1/5.

.TP 0.5i
.B xoscope oscope.dat

This runs xoscope, loading settings and memory buffers from a
previously saved data file called "oscope.dat".

.SH FILES
.B Xoscope
creates readable text data files.  The files contain at least a
comment header which holds the current settings of
.B xoscope.
Loading the file causes these saved settings to be restored.

To record your signals permanently first store them into memory
buffers, optionally recall them to channels, and then save the file.
All non-empty memory buffers are written to a column of the file
following the comment header.  Columns are separated by tab
characters.  These are stored back into the memory buffers when the
file is later loaded.  Simply recall them to channels to view them.
.P

This format could also be read by some spreadsheet or plotting
programs.  For example, the
.B gnuplot (1)
command
.P

plot "oscope.dat" using 0:1, "oscope.dat" using 0:2
.P

would plot the first and second columns of the "oscope.dat" data file.

.SH ENVIRONMENT

.TP 0.5i
.B OSCOPEPATH
The path to use when looking for external math commands.  If unset,
the built-in default is used.

.TP 0.5i
.B ESPEAKER
The host:port of the EsounD to connect to if built with EsounD
support.  If unset, localhost is assumed.  If no EsounD connection is
made or if there is no EsounD support compiled in, then
.B xoscope
will try to read /dev/dsp directly.

.SH LIMITATIONS

The sound card should be capable of 44100 Hz sampling via the sound
drivers.  You must use an external mixer program to select the input
source device, level, etc.  Since these unknowns affect the amplitude,
there is no reference to voltage on the Y axis; it is in fact,
unknown.  Instead you're given the scale in pixels per sample unit.
Note that the serial oscilloscope devices don't have this limitation.
They have real voltage labels on the Y axis.
.P

Signal math is only valid if Channel 1 and 2 contain signals of the
same sampling rate.
.B It is up to you to make sure this is the case.  Doing math on signals
.B of different sample rates will produce incorrect results!
.P

The automatic measurements count zero crossings and divide to
determine the frequency and period.  If these zero crossings are not
"regularly-periodic", these measurements could be invalid.
.B Xoscope
does understand how to measure the built-in FFT functions by locating
the peak frequency.  Use manual cursor positioning to get more precise
measurements.
.P

Your sound card is most-likely AC coupled so you will never see any DC
offset.  You probably can't get DC coupling by just shorting the input
capacitors on your sound card.  Use serial hardware to see DC offsets.
.P

The display may not be able to keep up if you give it too much to
plot, depending on your sound card, graphics card, and processor
speed.  External math commands are particularly expensive since the
kernel must then split the available CPU cycles across multiple
processes.  To maximize refresh speed, hide all unneeded channels, use
point or point accumulate mode, zoom in on Sec/Div as much as
possible, and turn off the graticule.
.P

.SH BUGS
The keyboard interface may be confusing.

.SH AUTHOR
.B Oscope
was written by Tim Witham (twitham@quiknet.com), originally based
on "scope" by Jeff Tranter (Jeff_Tranter@Mitel.COM).
Most recent work is by Brent Baccala (cosine@freesoft.org).
ALSA support by Gerhard Schiller (gerhard.schiller@gmail.com).
.B Xoscope
is released under the conditions of the GNU General Public License.
See the files README and COPYING in the distribution for details.

.\" xoscope.1 ends here.