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authorMauro Carvalho Chehab <mchehab@infradead.org>2006-05-22 10:31:37 -0300
committerMauro Carvalho Chehab <mchehab@infradead.org>2006-06-25 01:59:48 -0300
commit447d6fb8ccdc3a581a13fe4b5a62c384dc9fd36a (patch)
tree24163c66d1d1f27241c2a5c640175f3f7f42ce31 /Documentation/video4linux/cx88
parentb8d4c235d50f8512bbc9d67730c24da3309b0307 (diff)
V4L/DVB (3809b): Added missing docs at kernel tree
Date: From: Mauro Carvalho Chehab <mchehab@infradead.org> There are some docs at V4L/DVB tree that were never included at kernel. This patch includes those docs. Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'Documentation/video4linux/cx88')
-rw-r--r--Documentation/video4linux/cx88/hauppauge-wintv-cx88-ir.txt54
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/video4linux/cx88/hauppauge-wintv-cx88-ir.txt b/Documentation/video4linux/cx88/hauppauge-wintv-cx88-ir.txt
new file mode 100644
index 00000000000..93fec32a118
--- /dev/null
+++ b/Documentation/video4linux/cx88/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
+