[media] cx88.rst: add contents of hauppauge-wintv-cx88-ir.txt

Import the contents of hauppauge-wintv-cx88-ir.txt, after converted to ReST into cx88.rst file. Signed-off-by: Mauro Carvalho Chehab <[email protected]>
jledet · Jul 18, 2016 · f0d1722 · f0d1722
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diff --git a/Documentation/media/v4l-drivers/cx88.rst b/Documentation/media/v4l-drivers/cx88.rst
@@ -98,3 +98,65 @@ MO_OUTPUT_FORMAT (0x310164)
 0x47 is the sync byte for MPEG-2 transport stream packets.
 Datasheet incorrectly states to use 47 decimal. 188 is the length.
 All DVB compliant frontends output packets with this start code.
+
+Hauppauge WinTV cx88 IR information
+-----------------------------------
+
+The controls for the mux are GPIO [0,1] for source, and GPIO 2 for muting.
+
+====== ======== =================================================
+GPIO0  GPIO1
+====== ======== =================================================
+  0        0    TV Audio
+  1        0    FM radio
+  0        1    Line-In
+  1        1    Mono tuner bypass or CD passthru (tuner specific)
+====== ======== =================================================
+
+GPIO 16(I believe) is tied to the IR port (if present).
+
+
+From the data sheet:
+
+- Register 24'h20004  PCI Interrupt Status
+ - bit [18]  IR_SMP_INT Set when 32 input samples have been collected over
+ - gpio[16] pin into GP_SAMPLE register.
+
+What's missing from the data sheet:
+
+- Setup 4KHz sampling rate (roughly 2x oversampled; good enough for our RC5
+  compat remote)
+- set register 0x35C050 to  0xa80a80
+- enable sampling
+- set register 0x35C054 to 0x5
+- enable the IRQ bit 18 in the interrupt mask register (and
+  provide for a handler)
+
+GP_SAMPLE register is at 0x35C058
+
+Bits are then right shifted into the GP_SAMPLE register at the specified
+rate; you get an interrupt when a full DWORD is received.
+You need to recover the actual RC5 bits out of the (oversampled) IR sensor
+bits. (Hint: look for the 0/1and 1/0 crossings of the RC5 bi-phase data)  An
+actual raw RC5 code will span 2-3 DWORDS, depending on the actual alignment.
+
+I'm pretty sure when no IR signal is present the receiver is always in a
+marking state(1); but stray light, etc can cause intermittent noise values
+as well.  Remember, this is a free running sample of the IR receiver state
+over time, so don't assume any sample starts at any particular place.
+
+Additional info
+~~~~~~~~~~~~~~~
+
+This data sheet (google search) seems to have a lovely description of the
+RC5 basics:
+http://www.atmel.com/dyn/resources/prod_documents/doc2817.pdf
+
+This document has more data:
+http://www.nenya.be/beor/electronics/rc5.htm
+
+This document has a  how to decode a bi-phase data stream:
+http://www.ee.washington.edu/circuit_archive/text/ir_decode.txt
+
+This document has still more info:
+http://www.xs4all.nl/~sbp/knowledge/ir/rc5.htm
diff --git a/Documentation/video4linux/cx88/hauppauge-wintv-cx88-ir.txt b/Documentation/video4linux/cx88/hauppauge-wintv-cx88-ir.txt
diff --git a/Documentation/video4linux/hauppauge-wintv-cx88-ir.txt b/Documentation/video4linux/hauppauge-wintv-cx88-ir.txt