Date: Mon, 16 Oct 2006 12:25:02 -0500 From: "Rick C. Petty" <rick-freebsd@kiwi-computer.com> To: Ian Smith <smithi@nimnet.asn.au> Cc: freebsd-multimedia@freebsd.org Subject: Re: New port: pvrxxx for Hauppauge PVR150/500 Message-ID: <20061016172502.GB77730@keira.kiwi-computer.com> In-Reply-To: <Pine.BSF.3.96.1061016173539.15086A-100000@gaia.nimnet.asn.au> References: <20061016073124.GD23971@funkthat.com> <Pine.BSF.3.96.1061016173539.15086A-100000@gaia.nimnet.asn.au>
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On Mon, Oct 16, 2006 at 05:52:21PM +1000, Ian Smith wrote:
>
> Even bit-banging, I expect that it should be able to service interrupts
> between bytes - though not between bits, obviously - at least while
Why obviously? There's a clock line, so I can't see why pausing even
between the bits would hurt anything... so long as your transfer rate is
below the 400 kbit/s throughput. I've done a lot of Atmel AVR i2c myself,
even with direct bit-banging it seems to work just fine. Of course, if you
could offload the bus timing you would see a huge performance gain, but
that's not possible AFAIK in this case.
> transmitting. I have very little experience with iic, but am currently
> boning up on it for a board using two Atmel AVR processors connected by
> iic via optocouplers. Even long delays between transmitted bytes should
> be no problem unless the receiver has some unusual? timing requirements.
Just the 400 kbit/s max. Try inserting delays between the bits. It should
still work fine, as long as you transfer the appropriate number of bits.
> I've had a few quick forays through iicbb and all in /sys/dev/iicbus but
> admit to not making much sense of it compared to the simple AVR-asm code
> I've been studying, especially regarding the various bus layers, but it
> does appear that iicbb is pretty long in the tooth ('98?)
The iicbb could use some cleaning up. I could take a look at it if no one
else has the time/ability.
-- Rick C. Petty
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