[U-Boot-Users] I2C @ MPC8343

[Andre Schwarz <andre.schwarz@matrix-vision.de>]

Wolfgang,

I have indeed a LM75 on this bus - but it's not adressed.
The same I2C bus works fine on linux-2.6.25 including LM75 and EEPROM.

The oszi shows complete transactions with valid data.
I think it is as software issue.

Thanks,
Andre

w.wegner at astro-kom.de schrieb:
> Hi,
>
> On 10 Apr 2008 at 13:08, Martin Krause wrote:
>   
>>> After some tries (i2c md ..) the bus hangs and no more transactions
>>> can 
>>> be seen on the bus.
>>>       
>> One reason for a hanging bus could be a lost clock pulse. This could
>> happen, if the low->high rise time of the bus signal is longer than
>> the clock pulse width. For testing you could try a lower bus clock 
>> (10 kHz for example).
>>     
>
> sorry if I did not follow the discussion up to here. As I stumbled over
> it yesterday, I just want to give another example how to hang a bus.
>
> There are devices (namely LM75) that claim to be I2C devices but
> do not care about I2C specification. In case of LM75, a read must
> always be 16 bit (2 bytes), in case of reading only 1 byte the device
> does not interpret the missing ACK correctly and, in case the
> last byte read is '0', it will block the bus until some more (worst
> case 8) SCL pulses follow.
>
> Maybe something like this could also happen in your case?
>
> Regards,
> Wolfgang
>
>   



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