Lpc2000

I am trying to get a LPC2106 to talk to a PCF8574A chip which is 8 bit
I/O expander. I cant seem to get any thing to happen when using the
I2C example posted in the files section here.

Do I need external pull up resistors on the scl and sda lines?

What initiates a transfer? setting the STA bit in I2CONSET? 

Would it be better to use an interupt driven approach? or just
directly control it in my main loop if I know exactly when I want to
recieve data? 

Thanks 
Josiah

Hi Josiah,

> Do I need external pull up resistors on the scl and sda lines?

Yes, they're open drain pins (even when GPIO !)

The rest I don't know, haven't needed the I2C yet...

-- Kris

Josiah,

Note that manufacturers code on the "A" version of this part is 7 and not 4 
as in code examples for the non "A" PCF8574.

Mike

At 11:46 AM 5/16/2004, you wrote:

>I am trying to get a LPC2106 to talk to a PCF8574A chip which is 8 bit
>I/O expander. I cant seem to get any thing to happen when using the
>I2C example posted in the files section here.
>
>Do I need external pull up resistors on the scl and sda lines?
>
>What initiates a transfer? setting the STA bit in I2CONSET?
>
>Would it be better to use an interupt driven approach? or just
>directly control it in my main loop if I know exactly when I want to
>recieve data?
>
>Thanks
>Josiah
>
>
>
>
>
>Yahoo! Groups Links
>
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>
>