1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/video4linux/hauppauge-wintv-cx88-ir.txt b/Documentation/video4linux/hauppauge-wintv-cx88-ir.txt
new file mode 100644
index 000000000000..93fec32a1188
--- /dev/null
+++ b/Documentation/video4linux/hauppauge-wintv-cx88-ir.txt
@@ -0,0 +1,54 @@
+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
+
+Of course, 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 recieved.
+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.
+
+http://www.atmel.com/dyn/resources/prod_documents/doc2817.pdf
+This data sheet (google search) seems to have a lovely description of the
+RC5 basics
+
+http://users.pandora.be/nenya/electronics/rc5/  and more data
+
+http://www.ee.washington.edu/circuit_archive/text/ir_decode.txt
+and even a reference to how to decode a bi-phase data stream.
+
+http://www.xs4all.nl/~sbp/knowledge/ir/rc5.htm
+still more info
+