[U-Boot-Users] PXA255 and I2C

Anders Larsen alarsen at rea.de
Tue Jul 13 10:07:12 CEST 2004

Herb Radford <herbr at magma.ca> schreibt:
>I'm having some difficulty getting the I2C bus working on a PXA255-based 
>board. I also find I'm somewhat confused by the documentation on the I2C
>Intel's documents.
>I'm using an M41ST85 for the RTC chip. When I attempt to read from the
>I get timeouts and when I check the SCK, I find there's no activity at
>Digging into the documentation, it's not too clear how the GPIO's should
>set for I2C. GP25 is the SSPTX pin which is (I assume) made bidirectional 
>(somehow) when the I2C is enabled. Should it and GP23 (SSPCK) be set to 
>alternate function 2 (I assume so)?

Hi Herb, 

the I2C bus uses the SDA/SCL signals (pins A11/D11 - see chapter 9
in the PXA255 Processor Manual).
It has nothing to do with the Network SSP (described in chapter 16) that
uses the signals you mentioned above.
>I'm getting nothing on the I2C clock line when I transmit, but the I2C
>line does go high when enabled.

Probing the wrong pin?


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