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authorWerner Almesberger <werner@almesberger.net>2015-03-11 23:35:32 -0300
committerWerner Almesberger <werner@almesberger.net>2015-03-11 23:35:32 -0300
commitbd18ed9bdd058179e98faaa7dccde1b6163258e7 (patch)
tree6bba2ae7161cbda4b8c3d0e26de9cf5469978910 /ir
parent49153a0749a982dac1563b1f5b7c22f1bccd78ef (diff)
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ir/filter.fig, ir.tex: rewrite IR filter diagram and "Received signal processing" section
Diffstat (limited to 'ir')
-rw-r--r--ir/filter.fig86
-rw-r--r--ir/ir.tex23
2 files changed, 55 insertions, 54 deletions
diff --git a/ir/filter.fig b/ir/filter.fig
index d176f15..80b4e56 100644
--- a/ir/filter.fig
+++ b/ir/filter.fig
@@ -7,56 +7,56 @@ A4
Single
-2
1200 2
-2 2 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
- 5175 6300 5625 6300 5625 6750 5175 6750 5175 6300
2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
- 5265 6390 5265 6660 5535 6660
+ 8730 6390 8910 6390 9090 6030
+2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
+ 9180 6030 9000 6030 8820 6390
+2 3 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 4
+ 8640 5625 8640 6795 9675 6210 8640 5625
2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 5625 6525 6075 6525
-2 3 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
- 4725 5715 4725 6705 4275 6525 4275 5895 4725 5715
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
- 3825 6975 4500 6975 4500 6615
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
- 5625 5895 6075 5895 6075 7200
+ 7830 6210 8640 6210
2 2 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
- 5175 5670 5625 5670 5625 6120 5175 6120 5175 5670
+ 7200 5895 7830 5895 7830 6525 7200 6525 7200 5895
2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
- 5265 5760 5265 6030 5535 6030
+ 7290 5985 7290 6435 7740 6435
2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 5175 5895 4725 5895
+ 5940 6210 7200 6210
2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 5175 6525 4725 6525
+ 9675 6210 10215 6210
2 2 0 3 0 7 50 -1 -1 0.000 0 0 7 0 0 5
- 6660 5985 7290 5985 7290 6435 6660 6435 6660 5985
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 7 0 0 2
- 7380 6165 7470 6120
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 6660 6210 6075 6210
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 7 0 0 2
- 7380 6255 7470 6210
-2 3 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 4
- 3825 5985 3825 6435 3420 6210 3825 5985
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 4275 6210 3825 6210
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
- 3465 6210 3150 6210 3150 5625
+ 5310 5985 5940 5985 5940 6435 5310 6435 5310 5985
+2 1 0 2 0 7 50 -1 -1 0.000 0 0 7 1 0 2
+ 1 1 2.00 15.00 15.00
+ 5535 5760 5580 5895
+2 1 0 2 0 7 50 -1 -1 0.000 0 0 7 1 0 2
+ 1 1 2.00 15.00 15.00
+ 5625 5760 5670 5895
+2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
+ 0 0 3.00 150.00 150.00
+ 6525 6210 6525 6975
2 2 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
- 3060 5220 3240 5220 3240 5625 3060 5625 3060 5220
-2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
- 3150 4725 3150 5220
-3 2 0 2 0 7 50 -1 -1 0.000 0 0 0 3
- 5397 6623 5436 6465 5535 6435
- 0.000 -1.000 0.000
+ 10620 6120 10620 6300 10215 6300 10215 6120 10620 6120
+2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 1 0 3
+ 0 0 3.00 150.00 150.00
+ 10620 6210 11205 6210 11205 5400
+2 1 0 3 0 7 50 -1 -1 0.000 0 0 -1 1 0 3
+ 0 0 3.00 150.00 150.00
+ 10125 7200 9135 7200 9135 6525
+2 1 0 2 0 7 40 -1 -1 0.000 0 0 -1 1 0 2
+ 1 1 2.00 30.00 30.00
+ 8910 6390 9000 6210
+2 1 0 2 0 7 40 -1 -1 0.000 0 0 -1 1 0 2
+ 1 1 2.00 30.00 30.00
+ 9000 6030 8910 6210
3 2 0 2 0 7 50 -1 -1 0.000 0 0 0 3
- 5310 5985 5392 5829 5535 5805
+ 7409 6383 7544 6068 7724 6023
0.000 -1.000 0.000
-4 1 0 50 -1 22 12 0.0000 4 135 1005 6075 7380 Audio codec\001
-4 1 0 50 -1 22 12 0.0000 4 135 90 4500 6525 0\001
-4 1 0 50 -1 22 12 0.0000 4 135 90 4500 6030 1\001
-4 1 0 50 -1 22 12 0.0000 4 135 510 5400 5580 ~10 Hz\001
-4 1 0 50 -1 22 12 0.0000 4 135 600 5400 6975 ~20 kHz\001
-4 1 0 50 -1 22 12 0.0000 4 135 165 6975 6210 IR\001
-4 1 0 50 -1 22 12 0.0000 4 105 540 7020 6345 sensor\001
-4 1 0 50 -1 22 12 0.0000 4 135 225 3150 4680 RX\001
-4 2 0 50 -1 22 12 0.0000 4 135 690 3780 7065 IR-UART\001
+4 1 0 50 -1 22 12 0.0000 4 135 1005 6525 7155 Audio codec\001
+4 1 0 50 -1 22 12 0.0000 4 105 540 5625 6345 sensor\001
+4 1 0 50 -1 22 12 0.0000 4 135 165 5625 6210 IR\001
+4 1 0 50 -1 22 12 0.0000 4 135 1215 9000 5490 Level detection\001
+4 1 0 50 -1 22 12 0.0000 4 135 225 11205 5355 RX\001
+4 1 0 50 -1 22 12 0.0000 4 135 510 7515 6750 ~10 Hz\001
+4 1 0 50 -1 22 12 0.0000 4 180 1485 7515 5760 Ambient light filter\001
+4 0 0 50 -1 22 12 0.0000 4 180 645 10170 7245 bq.GPIO\001
+4 1 0 50 -1 22 12 0.0000 4 180 1050 10395 6525 Pull-up if idle\001
diff --git a/ir/ir.tex b/ir/ir.tex
index 211fe09..4621b01 100644
--- a/ir/ir.tex
+++ b/ir/ir.tex
@@ -244,21 +244,22 @@ a pulse therefore has to be limited. We discuss this in section \ref{overload}.
% RX, via proper signal shaping/filtering.
% and possibly also to audio-in
-On the receiving side, the signal should in CIR or IrDA mode go through a
-high-pass filter with
-a cutoff frequency of about 20 kHz and then be shaped into a digital
-signal for the RX line. The unfiltered analog signal should also be sent to
-an unused input of the audio codec. We have no further specification for the
-analog signal from the IR sensor at this time.
+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
+remote control and sends the resulting digital signal to the RX
+line.
\begin{center}
\includegraphics[scale=0.9]{filter.pdf}
\end{center}
-%
-Given that IR-UART can have very long high or low pulses, a high-pass
-filter with a much lower cut-off frequency has to be used when IR-UART mode
-is selected. A cut-off frequency of about 1--100 Hz should be sufficient
-for DC blocking. The figure above illustrates the concept.
+
+The series resistor ensures that CPU and Hackerbus can override the IR
+receiver. When the receiver is not illuminated or when it is disabled,
+the circuit outputs a high level and thus acts as a pull-up for the
+RX line.
+
+The unfiltered analog signal should also be sent to an unused input of
+the audio codec.
% Analog IR RX TBD
%