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authorWerner Almesberger <werner@almesberger.net>2015-03-14 06:46:20 -0300
committerWerner Almesberger <werner@almesberger.net>2015-03-14 06:46:20 -0300
commit7d70682e30d87204e1e441c7f6c7ecbd68fe1a07 (patch)
treeb833346cfbdef7345f710512f24adbd835c575ad /ir
parent947ecb8d543fcd728c73fea0842fc38754f5fe2a (diff)
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ir/ir.tex: clarified ambient light suppression; emphasize bottom view of chamber
Diffstat (limited to 'ir')
-rw-r--r--ir/ir.tex14
1 files changed, 11 insertions, 3 deletions
diff --git a/ir/ir.tex b/ir/ir.tex
index 60b7c6f..46eca24 100644
--- a/ir/ir.tex
+++ b/ir/ir.tex
@@ -252,7 +252,12 @@ a pulse therefore has to be limited. We discuss this in section \ref{overload}.
% and possibly also to audio-in
On the receiving side, a high-pass filter suppresses the effects of ambient
-light. A Schmitt-trigger then detects the strong pulses generated by the
+light.%
+\footnote{The receiver is designed to be insensitive to constant ambient light
+like strong sunlight, as well as common incandescent and fluorescent lamps.
+LED lamps may create interference when they are PWM-controlled and create a
+sufficient brightness level at the receiver diode.}
+ A Schmitt-trigger then detects the strong pulses generated by the
remote control and sends the resulting digital signal to the RX
line. The following drawing shows the general structure of the receiver
circuit:
@@ -446,7 +451,8 @@ UART mode configuration is illustrated in the following drawing:
Please note that, in order to avoid conflicts with use of the RX line,
the IR sensor has to be either disabled by setting bq.GPIO to ``0''
-or it must not be illuminated.
+or it must not be illuminated by a light source that excites the
+receiver.
% - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -575,7 +581,9 @@ if placed behind each other:
The transmitter should be closer to the window since its performance
is more important than that of the receiver.
-The following drawing shows a bottom view of the chamber that contains
+The following drawing shows a {\bf bottom view} (i.e., we look from the
+PCB at the bottom of the components and into the plastic case) of the
+chamber that contains
the IR diodes. The indicated placement maintains a clearance of at
least 5 mm between components and between components and walls.