MIDI documentation (still WIP, on-going)

wpwrak · wpwrak · commit d64b32746f7a · 2012-02-13T21:33:30.000-03:00
diff --git a/src/compiler/doc/Makefile b/src/compiler/doc/Makefile
@@ -10,15 +10,15 @@ PICS = arch msg bind stim \
        pot-0 pot-90 pot-180 pot-270 \
        enc-0 enc-90 enc-270 enc-450 enc-405 \
        dial-0 dial-90 dial-180 dial-360 \
-       dial-405 dial-315
+       dial-405 dial-405-idle dial-315 dial-45 dial-135 dial-315f
 
 GEN = nocvars.inc
 
 .PHONY:			all xpdf clean
 
 all:			midi.pdf
 
-midi.pdf:		midi.tex $(PICS:%=%.$(PICEXT)) $(GEN)
+midi.pdf:		midi.tex floats.inc $(PICS:%=%.$(PICEXT)) $(GEN)
 			pdflatex midi
 
 xpdf:			midi.pdf
@@ -102,9 +102,21 @@ dial-360.$(PICEXT):	dial.fig
 dial-405.$(PICEXT):	dial.fig
 			$(call fig2pdf, 45deg cw-slow)
 
+dial-405-idle.$(PICEXT): dial.fig
+			$(call fig2pdf, 45deg)
+
 dial-315.$(PICEXT):	dial.fig
 			$(call fig2pdf, 315deg ccw)
 
+dial-45.$(PICEXT):	dial.fig
+			$(call fig2pdf, 45deg ccw-slow)
+
+dial-135.$(PICEXT):	dial.fig
+			$(call fig2pdf, 135deg ccw-fast)
+
+dial-315f.$(PICEXT):	dial.fig
+			$(call fig2pdf, 315deg ccw-fast)
+
 nocvars.inc:		../fnp.ids
 			./mknocvars <$< >$@ || { rm -f $@; exit 1; }
 
diff --git a/src/compiler/doc/arch.fig b/src/compiler/doc/arch.fig
@@ -22,32 +22,32 @@ Single
 1 1 0 3 0 7 50 -1 -1 0.000 1 0.0000 4050 3825 675 450 4050 3825 4725 4275
 4 1 0 45 -1 18 12 0.0000 4 150 1050 4050 3915 Translation\001
 -6
-6 6480 2205 8370 4995
+6 6480 2655 8370 5445
 2 2 0 2 0 7 55 -1 -1 0.000 0 0 -1 0 0 5
-	 6525 2250 8325 2250 8325 4950 6525 4950 6525 2250
-4 0 0 45 -1 18 12 0.0000 4 195 1560 6750 2925 var = range(aux);\001
-4 0 32 55 -1 18 12 0.0000 4 195 990 6750 3240 per_frame:\001
-4 0 32 55 -1 18 12 0.0000 4 180 960 6975 3555 rot = time;\001
-4 0 32 55 -1 18 12 0.0000 4 135 1110 6975 3870 zoom = var;\001
-4 0 32 55 -1 18 12 0.0000 4 105 840 6750 2610 ...more...\001
-4 0 32 55 -1 18 12 0.0000 4 105 840 6975 4185 ...more...\001
+	 6525 2700 8325 2700 8325 5400 6525 5400 6525 2700
+4 0 0 45 -1 18 12 0.0000 4 195 1560 6750 3375 var = range(aux);\001
+4 0 32 55 -1 18 12 0.0000 4 195 990 6750 3690 per_frame:\001
+4 0 32 55 -1 18 12 0.0000 4 180 960 6975 4005 rot = time;\001
+4 0 32 55 -1 18 12 0.0000 4 135 1110 6975 4320 zoom = var;\001
+4 0 32 55 -1 18 12 0.0000 4 105 840 6750 3060 ...more...\001
+4 0 32 55 -1 18 12 0.0000 4 105 840 6975 4635 ...more...\001
 -6
-6 1305 3825 1665 4185
-1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1485 4005 127 127 1485 4005 1395 3915
+6 1305 3915 1665 4275
+1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1485 4095 127 127 1485 4095 1395 4005
 2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
-	 1485 4005 1395 3915
+	 1485 4095 1395 4005
 -6
-6 1485 3285 1665 3600
-5 1 0 2 0 7 50 -1 -1 0.000 0 0 0 0 1575.000 3375.000 1530 3375 1575 3330 1620 3375
-5 1 0 2 0 7 50 -1 -1 0.000 0 1 0 0 1575.000 3510.000 1530 3510 1575 3555 1620 3510
-1 3 0 2 0 7 47 -1 15 0.000 1 0.0000 1575 3375 45 45 1575 3375 1620 3375
+6 945 3330 1260 3510
+5 1 0 2 0 7 50 -1 -1 0.000 0 0 0 0 1035.000 3420.000 1035 3465 990 3420 1035 3375
+5 1 0 2 0 7 50 -1 -1 0.000 0 1 0 0 1170.000 3420.000 1170 3465 1215 3420 1170 3375
+1 3 0 2 0 7 47 -1 15 0.000 1 1.5708 1035 3420 45 45 1035 3420 1035 3375
 2 1 0 2 0 7 49 -1 -1 0.000 0 0 -1 0 0 2
-	 1530 3375 1530 3510
+	 1035 3465 1170 3465
 2 1 0 2 0 7 49 -1 -1 0.000 0 0 -1 0 0 2
-	 1620 3375 1620 3510
+	 1035 3375 1170 3375
 -6
-1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1080 3420 90 90 1080 3420 1170 3420
-1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1350 3420 90 90 1350 3420 1440 3420
+1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1530 3420 90 90 1530 3420 1620 3420
+1 3 0 2 0 7 50 -1 -1 0.000 1 0.0000 1530 3690 90 90 1530 3690 1620 3690
 2 1 0 2 0 7 53 -1 -1 0.000 0 0 -1 0 0 2
 	 3600 5355 4725 5355
 2 1 0 2 0 7 53 -1 -1 0.000 0 0 -1 0 0 2
@@ -71,19 +71,19 @@ Single
 	 1890 3825 3330 3825
 2 1 0 2 0 7 50 -1 -1 0.000 0 0 7 1 0 3
 	1 1 2.00 60.00 60.00
-	 4770 3825 6885 3825 6885 2970
-2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 1 0 3
-	1 1 2.00 60.00 60.00
-	 6705 2880 4050 2880 4050 3330
-2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 4770 3825 6885 3825 6885 3420
+2 1 0 2 0 7 50 -1 -1 0.000 0 1 -1 0 0 2
 	 1080 4320 1080 3645
-2 1 0 4 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+2 1 0 4 0 7 50 -1 -1 0.000 0 1 -1 0 0 2
 	 990 4095 1170 4095
 2 2 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
 	 810 3150 1800 3150 1800 4500 810 4500 810 3150
+2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 1 0 4
+	1 1 2.00 60.00 60.00
+	 7470 3195 7470 2880 4050 2880 4050 3330
 4 1 0 45 -1 18 12 0.0000 4 150 525 12330 6570 Patch\001
-4 1 0 45 -1 18 12 0.0000 4 150 435 3285 5355 dev1\001
-4 1 0 45 -1 18 12 0.0000 4 150 435 3285 6480 dev2\001
+4 1 0 45 -1 18 12 0.0000 4 150 615 3285 5355 Gizmo\001
+4 1 32 45 -1 18 12 0.0000 4 150 435 3285 6480 Frob\001
 4 0 0 45 -1 18 12 0.0000 4 150 1380 4185 4725 Characteristics\001
 4 1 0 45 -1 18 12 0.0000 4 150 630 2610 3735 Events\001
 4 1 0 45 -1 18 12 0.0000 4 150 1500 3960 7470 Device database\001
diff --git a/src/compiler/doc/bind.fig b/src/compiler/doc/bind.fig
@@ -136,15 +136,15 @@ Single
 4 1 0 50 -1 18 12 0.0000 4 150 690 5400 6255 MIDICC\001
 4 1 0 50 -1 18 12 0.0000 4 135 315 6300 6255 103\001
 4 1 0 50 -1 18 12 0.0000 4 195 300 6750 6255 pot\001
-4 1 0 45 -1 18 12 0.0000 4 150 435 4185 6030 dev1\001
+4 1 0 45 -1 18 12 0.0000 4 150 615 4185 6030 Gizmo\001
 4 1 0 50 -1 18 12 0.0000 4 150 1050 10350 3555 Translators\001
 4 1 0 30 -1 14 20 0.0000 4 270 3315 5625 4050 var = range(aux);\001
 4 1 0 50 -1 18 12 0.0000 4 150 525 4815 6030 Name\001
 4 1 0 50 -1 18 12 0.0000 4 195 450 5355 6030 Type\001
 4 1 0 50 -1 18 12 0.0000 4 150 345 6750 6030 Dev\001
 4 1 0 50 -1 18 12 0.0000 4 150 330 6345 6030 Ctrl\001
 4 1 0 50 -1 18 12 0.0000 4 150 480 5895 6030 Chan\001
-4 1 0 45 -1 18 12 0.0000 4 150 435 4185 7380 dev2\001
+4 1 32 45 -1 18 12 0.0000 4 150 435 4185 7380 Frob\001
 4 1 0 50 -1 18 12 0.0000 4 150 1500 5490 8820 Device database\001
 4 1 0 50 -1 18 12 0.0000 4 150 330 8955 8370 Ctrl\001
 4 1 0 50 -1 18 12 0.0000 4 150 435 9450 8370 Proc\001
diff --git a/src/compiler/doc/floats.inc b/src/compiler/doc/floats.inc
@@ -0,0 +1,38 @@
+\newcommand{\figarch}{
+\begin{figure}[!tb]
+\begin{center}
+\includegraphics{arch.pdf}
+\end{center}
+\caption{Input event processing in Flickernoise.}
+\label{arch}
+\end{figure}}
+
+\newcommand{\figmsg}{
+\begin{figure}[!tb]
+\begin{center}
+\includegraphics{msg.pdf}
+\end{center}
+\caption{Anatomy of a MIDI Control Change message.}
+\label{msg}
+\end{figure}}
+
+\newcommand{\figbind}{
+\begin{figure}[!tb]
+\begin{center}
+\includegraphics{bind.pdf}
+\end{center}
+\caption{When binding a control variable, information from the device
+  database, a translation map, and the table of patch variables is
+  combined into a stimulus entry.}
+\label{bind}
+\end{figure}}
+
+\newcommand{\figstim}{
+\begin{figure}[!tb]
+\begin{center}
+\includegraphics{stim.pdf}
+\end{center}
+\caption{When a MIDI control message is received, Flickernoise looks
+  for a matching stimulus and processes the value accordingly.}
+\label{stim}
+\end{figure}}
diff --git a/src/compiler/doc/midi.tex b/src/compiler/doc/midi.tex

-Original file line number
+Diff line change
 \usepackage{fullpage}
 \usepackage{parskip}
 \usepackage{booktabs}
 -\usepackage{epsfig}
 \usepackage{moreverb}
 \usepackage{nicefrac}
 \newenvironment{expose}{\vskip3mm\qquad\begin{raggedright}}{%
 \end{raggedright}\vskip3mm}
 +\input floats.inc
++
 \begin{document}
 \title{Using MIDI in Flickernoise Patches}
 \maketitle
 -\begin{abstract}
 -This document describes how MIDI
 -\end{abstract}
+-
 %\setcounter{tocdepth}{1}
 \tableofcontents
   \item the MIDI device specifications should not have to be part of
     patches,
   \item Flickernoise should only consider devices that are really present, and
 -  \item we should support other events that just MIDI control message,
 +  \item we should support other events than just MIDI control message,
     such as other MIDI message types, DMX, keyboard, IR remote, etc.
 \end{itemize}
 	aux = pot(103);
 	but1 = button(16);
 	but2 = button(17);
 +	select = switch(24);
+}
 sensitivity = range(main);
 In lines 1 through 6 we describe the controls the MIDI device called
 ``Gizmo'' provides. In this case, we have one fader, one potentiometer,
 -and two buttons. We assign them names that represent their role: {\tt main}
 +two buttons, and one switch. We assign them names that represent their
 +role: {\tt main}
 for the principal fader, {\tt aux} for the potentiometer, and so on.
 The numbers are the respective MIDI controller numbers the device uses.
 They can be found with the MIDI monitor function of the ``MIDI settings''
 dialog in Flickernoise.
 -In line 8, we bind the {\tt main} control to a variable. This variable is
 -then used in per-frame and per-vertex equations. As line 12 shows, one
 +In line 9, we bind the {\tt main} control to a variable. This variable is
 +then used in per-frame and per-vertex equations. As line 13 shows, one
 can also change this variable, e.g., to make the sensitivity slowly decay
 if there is no input from the MIDI device.
 % -----------------------------------------------------------------------------
 +\figarch
++
++
 \section{Architecture}
 -When a MIDI device is1
 -\begin{figure}[!tb]
 -\begin{center}
 -\includegraphics{arch.pdf}
 -\end{center}
 -\caption{Input event processing in Flickernoise.}
 -\label{arch}
 -\end{figure}
 +For each MIDI device, an entry in the device database is selected.
 +This entry describes the characteristics of the elements of the MIDI
 +device, e.g., what kind of control elements they are and what
 +addresses they use.
++
 +A patch using MIDI devices binds control elements to variables.
 +When binding, the patch specifies how it expects the element to
 +behave, e.g., whether it should produce continuous values between
 +0 and 1 or just 0 when ''off'' and 1 when ''on''.
++
 +Event messages from the MIDI device identify the element they
 +belong to and carry a numeric value indicating the element's state.
 +This value is translated according to the element's characteristics
 +from the device database combined with the expected function from
 +the patch.
++
 +Finally, result is stored in the control variable where it can
 +then be used by the equations in the patch.
 % - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 +\figmsg
++
++
 \subsection{MIDI control messages}
 A MIDI device sends a message each time one of its elements is actuated.
 MIDI device generates a MIDI Control Change messages, as shown in
 figure \ref{msg}.
 -\begin{figure}[!tb]
 -\begin{center}
 -\includegraphics{msg.pdf}
 -\end{center}
 -\caption{Anatomy of a MIDI Control Change message.}
 -\label{msg}
 -\end{figure}
+-
 Channel numbers are encoded as values from 0 to 15 in the actual
 MIDI message but are commonly presented as 1 to 16 to the user.
 Also Flickernoise follows this convention.
 % - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 -\subsection{@@@}
 +\subsection{Control variables}
 +Patches communicate with the outside world though variables. MIDI
 +control input is no exception. Instead of using pre-defined names
 +like it is the case for {\tt time}, {\tt bass}, etc., the names of
 +MIDI control variables can be chosen freely.
++
 +Values from MIDI controls are usually translated to
 +the range 0 to 1. This can be as simple a division by 127.
 +Section \ref{binding} describes more ways to translate MIDI messages.
++
 +Updates of control variables are synchronized with patch execution
 +such that updates never happen while the patch is running.
 -@@@
 % -----------------------------------------------------------------------------
 @@@
++
++
 % - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 {\em channel} is the MIDI channel number, from 1 to 16. If the channel
 is omitted, the element will match any channel.
 +{\em control\_number}
++
 +This is the example from the quick start section with channel numbers
 +added:
++
 \begin{listing}{1}
 -midi "dev1" {
 +midi "Gizmo" {
 	main = fader(1, 102);
 	aux = pot(1, 103);
 	but1 = button(1, 16);
 	but2 = button(1, 17);
 -	sw = switch(1, 24);
 +	select = switch(1, 24);
+}
 \end{listing}
 \subsection{Binding}
 +\label{binding}
 In order to use a control in a patch, we have to establish a connection
 between the control element (in the device database) and a patch
 {\em element\_name} is the name of the control element, as in the
 device database.
 -\begin{figure}[!tb]
 -\begin{center}
 -\includegraphics{bind.pdf}
 -\end{center}
 -\caption{When binding a control variable, information from the device
 -  database, a translation map, and the table of patch variables is
 -  combined into a stimulus entry.}
 -\label{bind}
 -\end{figure}
 +\figbind
++
 +@@@
 % - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 -\subsection{Event processing}
 +\figstim
 -\begin{figure}[!tb]
 -\begin{center}
 -\includegraphics{stim.pdf}
 -\end{center}
 -\caption{When a MIDI control message is received, Flickernoise looks
 -  for a matching stimulus and processes the value accordingly.}
 -\label{stim}
 -\end{figure}
 +\subsection{Event processing}
 Figure \ref{stim} illustrates how events are translated into changes
 of control variables.
 \subsection{Writing to control variables}
 -A patch can overwrite the values control variables. In the case of
 +A patch can overwrite the values of control variables. In the case of
 per-frame variables, they retain their modified content across
 frames until a new event arrives. The new event will always overwrite
 the previous value of the variable without regard for any changes that
 % -----------------------------------------------------------------------------
 -\section{Control devices}
 +\section{Control elements}
 -In the section below, we describe the various control elements, their
 -declaration, and their behaviour. In the example, we show the physical
 -state of the element, the value a MIDI control may typically send for
 -the element in that state, and then the resulting values for the
 -various translations.
 +In the sections below, we describe the various control elements, who
 +they are described in the device database, and their behaviour. We
 +give examples, that show the physical state of the element, the value
 +a MIDI control may typically send for the element in that state, and
 +then the resulting values for the various translations.
 Since {\tt range}, {\tt unbounded}, and {\tt cycle} only differ from
 each other in one case, they are usually abbreviated as just
 in the next section.
 The example below shows a potentiometer that travels over an angle
 -of $270^{\circ}$:
 +of $270^\circ$:
 \begin{expose}
 \begin{tabular}{lccccl}
 \subsection{Rotary encoders acting as potentiometers}
 +\label{encpot}
 Rotary encoders look similar to potentiometers but differ from them
 by not having a mechanical stop. This means that they can be turned
 {\tt pot} and bound with {\tt range}.
 The example below shows a rotary encoder covering the full value range
 -in one $360^{\circ}$ turn that is first turned $450^{\circ}$ clockwise
 -and then $45^{\circ}$ counterclockwise:
 +in one $360^\circ$ turn that is first turned $450^\circ$ clockwise
 +and then $45^\circ$ counterclockwise:
 \begin{expose}
 \begin{tabular}{lcccccl}
 \end{tabular}
 \end{expose}
 -Note that it stops at MIDI value 127 at the third turn and the
 -remaining $90^{\circ}$ are ignored.
 +The encoder stops at MIDI value 127 at the third turn and the
 +remaining $90^\circ$ are ignored.
++
 +Note that the the above is a bit simplified. Rotary encoders commonly
 +found in MIDI devices only have 20--30 positions per full turn. When
 +turning them slowly, it therefore takes several full turns to cross
 +the entire range. To permit quick changes, MIDI controllers usually
 +change the value in steps larger than one when the encoder is turned
 +rapidly.
 % - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 \subsection{Differential encoders}
 \label{diff}
 +The rotary encoders of some controllers send differential values
 +instead of the usual absolute values. Differential values allows
 +Flickernoise not only to translate them to absolute values, but
 +also enables more sophisticated translations.
++
 +Differential values are encoded as signed 7 bit numbers. This means
 +that values in the range 0--63 represent an increase by that amount
 +while values in the range 0--127 represent a decrease by 128 minus
 +the value. E.g., a value of 127 would mean a decrease by one.
++
 +Differential encoders are declared with {\tt differential()}:
++
 +\begin{listing}{1}
 +midi ... {
 +	name = differential(...);
 +}
 +\end{listing}
++
 +There are three distinct options for binding them to continuous values:
 +with {\tt range()}, the
 +emulate potentiometers with a range from 0 to 1. With {\tt unbounded},
 +the control variable can also assume values below 0 or above 1. Finally,
 +{\tt cyclic} limits the control variable to a range from 0 to 1 but
 +makes it wrap from 1 to 0 when increasing, and from 0 to 1 when
 +decreasing.
++
 +\begin{listing}{1}
 +var1 = range(name1);
 +var2 = unbounded(name2);
 +var3 = cyclic(name3);
 +\end{listing}
++
 +This example illustrates the values that result for the different
 +translations when turning an encoder that needs one $360^\circ$ turn
 +for the full value range by a total of $405^\circ$:
++
 \begin{expose}
 \begin{tabular}{lccccccl}
   \raisebox{6mm}{User input} &
   \includegraphics{dial-0.pdf} &
   \includegraphics{dial-90.pdf} &
   \includegraphics{dial-180.pdf} &
   \includegraphics{dial-360.pdf} &
 +  \includegraphics{dial-405.pdf} \\
 +  \cmidrule(r){1-6}
 +  MIDI value &
 +  & 32 & 32 & 63 & 16 \\
 +  \midrule
 +  Translation
 +  & 0 & 0.25 & 0.5 & 1 & 1 & \tt range \\
 +  & 0 & 0.25 & 0.5 & 1 & 1.125 & \tt unbounded \\
 +  & 0 & 0.25 & 0.5 & 0 & 0.125 & \tt cyclic \\
 +\end{tabular}
 +\end{expose}
++
 +Continuing the example above, we turn the controller now by
 +$90^\circ$ in a counterclockwise direction:
++
 +\begin{expose}
 +\begin{tabular}{lccl}
 +  \raisebox{6mm}{User input} &
 +  \includegraphics{dial-405-idle.pdf} &
 +  \includegraphics{dial-315.pdf} \\
 +  \cmidrule(r){1-3}
 +  MIDI value &
 +  & 96 \\
 +  \midrule
 +  Translation
 +  & 1 & 0.75 & \tt range \\
 +  & 1.125 & 0.875 & \tt unbounded \\
 +  & 0.125 & 0.875 & \tt cyclic \\
 +\end{tabular}
 +\end{expose}
++
 +Starting from zero again, we now turn the controller first
 +$45^\circ$ clockwise and then $450^\circ$ counterclockwise:
++
 +\begin{expose}
 +\begin{tabular}{lcccccl}
 +  \raisebox{6mm}{User input} &
 +  \includegraphics{dial-0.pdf} &
   \includegraphics{dial-405.pdf} &
 +  \includegraphics{dial-315.pdf} &
 +  \includegraphics{dial-135.pdf} &
 +  \includegraphics{dial-315f.pdf} \\
 +  \cmidrule(r){1-6}
 +  MIDI value &
 +  & 16 & 96 & 64 & 64 \\
 +  \midrule
 +  Translation
 +  & 0 & 0.125 & 0 & 0 & 0 & \tt range \\
 +  & 0 & 0.125 & -0.125 & -0.625 & -1.125 & \tt unbounded \\
 +  & 0 & 0.125 & 0.875 & 0.375 & 0.875 & \tt cyclic \\
 +\end{tabular}
 +\end{expose}
++
 +When emulation a button or a switch, any clockwise turn will set the
 +control variable to 1 while any counterclockwise turn will set it to
 +zero:
++
 +\begin{expose}
 +\begin{tabular}{lccccl}
 +  \raisebox{6mm}{User input} &
 +  \includegraphics{dial-0.pdf} &
 +  \includegraphics{dial-90.pdf} &
 +  \includegraphics{dial-45.pdf} &
   \includegraphics{dial-315.pdf} \\
 -  \cmidrule(r){1-7}
 +  \cmidrule(r){1-5}
   MIDI value &
 -  & 32 & 32 & 64 & 16 & 96 \\
 +  & 32 & 112 & 96 \\
   \midrule
   Translation
 -  & 0 & 0.25 & 0.5 & 1 & 1 & 0.75 & \tt range \\
 -  & 0 & 0.25 & 0.5 & 1 & 1.125 & 0.875 & \tt unbounded \\
 -  & 0 & 0.25 & 0.5 & 0 & 0.125 & 0.875 & \tt cyclic \\
 -%  & 0 & 1 & 1 & 0 & \tt button, switch \\
 +  & 0 & 1 & 0 & 0 & \tt button, switch \\
 \end{tabular}
 \end{expose}
 +Like the rotary encoders emulating potentiometers described in section
 +\ref{encpot}, the values a device sends for differential encoders may be
 +increased if turning rapidly.
++
 %   The control variable can assume any value, including negative
 %   values and values greater than one. This can be used with
 %   certain rotary encoders. If the device in question has no