Accessing I2C on a RiscPC - without a backplane

Arc/RPCs, peripherals, RISCOS operating system & ARM kit eg GP2x, BeagleBoard
nudelooney
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Accessing I2C on a RiscPC - without a backplane

Postby nudelooney » Tue Jul 11, 2017 10:03 pm

Hi,

I'd like to access the I2C bus on a RiscPC for a project, but it doesn't have a backplane. As I have lots of DIN41612C connectors, I was considering just connecting direct to the socket on the motherboard where the backplane would normally go.

Does anyone know if the backplane adds any extra circuitry (such as buffering or pullups) on the I2C bus?

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daveejhitchins
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Re: Accessing I2C on a RiscPC - without a backplane

Postby daveejhitchins » Wed Jul 12, 2017 4:15 am

Here's a copy of our A3000 (probably not up-to-date, however, IIC would not have changed). PL5 is the IIC connector. Hope that helps?

Dave H :D

Internal A3000 IDE Interface 4.jpg
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

nudelooney
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Re: Accessing I2C on a RiscPC - without a backplane

Postby nudelooney » Wed Jul 12, 2017 9:02 am

Hi Dave,

I don't know if that's helpful or not! My question was about a RiscPC. I know the expansion port on the back of the A3000 is going to be the same as the podule connectors in a RiscPC - but I don't know what components the RiscPC backplane itself provides (as far as I2C is concerned) between the RiscPC motherboard and those podule connectors.

Anyone have a schematic for the RiscPC backplane? My Google Fu is letting me down. :(

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IanS
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Re: Accessing I2C on a RiscPC - without a backplane

Postby IanS » Wed Jul 12, 2017 5:54 pm

Diagram of the podule backplane for the RISC PC is available here:-
http://chrisacorns.computinghistory.org ... uters.html
(follow the Technical Drawings link)

The motherboard backplane connector on the RISC PC (and A7000) is not a DIN41612, it's an edge connector socekt.

Doesn't appear to be any buffering or pull-ups on the backplane.

nudelooney
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Re: Accessing I2C on a RiscPC - without a backplane

Postby nudelooney » Thu Jul 13, 2017 9:57 am

Ah - thanks for that link! Those PDFs are perfect.

And yes, you're quite right - it's an edge connector. I'm losing my marbles!

Thank you very much, guys!


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