Editing Using the simulator indicator lamps

The simulator's '''Indicators''' section has two lamps, '''LED1''' and '''LED2''', which
follow the registers <code>REG30</code> and <code>REG31</code> as your program runs. They
give you a way to see a value you cannot hear — an envelope follower, a tempo, the state
of a switch.

== How brightness is worked out ==

The lamp reads its register as S1.23:

* '''0''' is off.
* '''1.0''' is full brightness.
* A negative value is off. It is not rectified, so a bipolar signal lights the lamp only
  on its positive half.

The scale is linear on purpose. A program that wants a curve is two instructions from the
curve it wants.

== Lighting a lamp ==

Write the value you want to see into <code>REG30</code> or <code>REG31</code>:

<pre>
; #LED1 Rate

skp     run, loop
wlds    sin0, 12, 32767

loop:
cho     rdal, sin0      ; bipolar, -1 to +1
sof     0.5, 0.5        ; fold to 0..1 so the lamp follows the whole cycle
wrax    reg30, 0
</pre>

Without the <code>sof 0.5, 0.5</code> the lamp is dark for half of every LFO cycle.

== Naming the lamps ==

A comment tag renames a lamp in the panel:

<pre>
; #LED1 Tempo
</pre>

The tag is read from the comment part of the line, so it never collides with code. It is
the same mechanism that names the pots — see
[[Labelling pots and lamps in your source]].

== A gotcha ==

Nothing on the FV-1 reserves <code>REG30</code> or <code>REG31</code>. A program that parks
scratch values there will light the lamps by accident. If a lamp flickers for no reason you
can explain, check whether those two registers are being used as general-purpose storage.

== See also ==
* [[Using the FV-1 simulator]]
* [[Controlling the simulator with MIDI]]

[[Category:How-to]]