Lpc2000

I'm trying to get I2c up and running on my 2106 board and am seeing 
strange things. Basically, when the LPC2106 brings SCL low I see the 
line dropping only to 1.5V rather than 0. I can verify this by 
switching P0.2 to GPIO mode and outputting 0.

SDA fluctuates between 0 and 3.3V as I would expect.

I do have another I2C master on the bus - a TI TUSB3410. When it drives 
I2C SCL fluctuates between 0 and 3.3V. The TI chip is in suspend mode 
at this point, as far as I know it shouldn't be impacting the I2C bus.

I have 10k pullups on SCL and SDA.

Does anyone have any ideas as to what might be causing this or where I 
can next look?

Thanks!

Shannon

Gah. It was the TI chip. Apparently TI believes that the way to 
implement I2C is to assert SCL high when not using the bus... Don't 
really need both of them to be on the same I2C bus (other than it 
seemed convenient and I can save two pullup resistors), but something 
that will be fixed with the next board rev...

Shannon

On Jul 1, 2004, at 4:44 PM, Shannon Holland wrote:

> I'm trying to get I2c up and running on my 2106 board and am seeing
> strange things. Basically, when the LPC2106 brings SCL low I see the
> line dropping only to 1.5V rather than 0. I can verify this by
> switching P0.2 to GPIO mode and outputting 0.
>
> SDA fluctuates between 0 and 3.3V as I would expect.
>
> I do have another I2C master on the bus - a TI TUSB3410. When it drives
> I2C SCL fluctuates between 0 and 3.3V. The TI chip is in suspend mode
> at this point, as far as I know it shouldn't be impacting the I2C bus.
>
> I have 10k pullups on SCL and SDA.
>
> Does anyone have any ideas as to what might be causing this or where I
> can next look?
>
> Thanks!
>
> Shannon
>
>
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>
>
> Yahoo! Groups Links
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