55 lines
1.9 KiB
Text
55 lines
1.9 KiB
Text
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The controls for the mux are GPIO [0,1] for source, and GPIO 2 for muting.
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GPIO0 GPIO1
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0 0 TV Audio
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1 0 FM radio
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0 1 Line-In
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1 1 Mono tuner bypass or CD passthru (tuner specific)
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GPIO 16(i believe) is tied to the IR port (if present).
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------------------------------------------------------------------------------------
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>From the data sheet:
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Register 24'h20004 PCI Interrupt Status
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bit [18] IR_SMP_INT Set when 32 input samples have been collected over
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gpio[16] pin into GP_SAMPLE register.
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What's missing from the data sheet:
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Setup 4KHz sampling rate (roughly 2x oversampled; good enough for our RC5
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compat remote)
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set register 0x35C050 to 0xa80a80
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enable sampling
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set register 0x35C054 to 0x5
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Of course, enable the IRQ bit 18 in the interrupt mask register .(and
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provide for a handler)
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GP_SAMPLE register is at 0x35C058
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Bits are then right shifted into the GP_SAMPLE register at the specified
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rate; you get an interrupt when a full DWORD is received.
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You need to recover the actual RC5 bits out of the (oversampled) IR sensor
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bits. (Hint: look for the 0/1and 1/0 crossings of the RC5 bi-phase data) An
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actual raw RC5 code will span 2-3 DWORDS, depending on the actual alignment.
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I'm pretty sure when no IR signal is present the receiver is always in a
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marking state(1); but stray light, etc can cause intermittent noise values
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as well. Remember, this is a free running sample of the IR receiver state
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over time, so don't assume any sample starts at any particular place.
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http://www.atmel.com/dyn/resources/prod_documents/doc2817.pdf
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This data sheet (google search) seems to have a lovely description of the
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RC5 basics
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http://www.nenya.be/beor/electronics/rc5.htm and more data
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http://www.ee.washington.edu/circuit_archive/text/ir_decode.txt
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and even a reference to how to decode a bi-phase data stream.
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http://www.xs4all.nl/~sbp/knowledge/ir/rc5.htm
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still more info
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