Hans-Bernhard Broeker wrote: : The Mind Factory INC wrote: :> Is there a simple method to interface to the PCI bus to be able to control :> something with a few bits like SPI or I2C, : : Not really. It'd hardly make much sense, anyway: it'd be like : interfacing a 40-ton truck engine to drive a 40 millimeter PC cooling : fan.
Not necessarily. It would make sence if the PCI bridge would fan out to a general purpose, low frequency, classic strobe line controlled bus that could accommodate multiple expansion cards. No wait - that's what the south bridge was all about, wasn't it?
Jokes aside, there is truth to this. The Wintel PC is rapidly becoming useless for embedded tinkering and interfacing. Which is ironic as it is exactly this property that made it popular in the first place despite all its flaws (actually, the PC used to be nothing but a collection of flaws.)
Even if the PC continued to maintain the ISA bus it would be to no avail. Apart from the many flaws in the ISA bus itself, the device driver model of the Windows line of operation systems are by now totally inaccesible to hardware geeks. The linux is still barely within reach, but I expect that to change as well.
I only see one way out: Ethernet. Reasonable simple to implement on the target, both hardware and software (protocol) wise, the biggest benefit is the accessibility directly from userland on desktop OSes. But I suppose that if hardware geeks really started to use this opportunity to bypass the desktop OS at large, this 'hole' will eventually be plugged, citing OS architectual benefits and streamlining...
:> I think there is some form of serial bus running around a mother :> board to do heat and fan monitoring, : : On *some* of them there is, but that's not guaranteed by anything. : It's typically I2C, but called the System Management Bus, or "SMB" for : short. : :> does this come out on the PCI connector? : : No.
But it *does* come out on the DD-/SDRAM DIMM connectors.