Re: ack/nack in write operation

[Michele Da Rold <michele.darold-jTUIOkKm3KASWr57yraSmw@public.gmane.org>]

Vendor resolve the problem.

Thank you for your help

Michele

Il 15/07/2011 10:03, Michele Da Rold ha scritto:
> Il 14/07/2011 18:26, Jean Delvare ha scritto:
>> On Thu, 14 Jul 2011 17:52:25 +0200, Michele Da Rold wrote:
>>> Hello everybody,
>>> I'm new to i2c development some don't kill me if my questions are
>>> stupid!!
>>>
>>> I'm using bitbanging i2c driver for an AT91 devices,
>>> the AT91 is master and I have a slave that reply, during a write, with a
>>> NAK after last byte.
>>> The i2c specification permit this solution but i2c linux driver no.
>>
>> Can you please quote the part of the I2C specification which you think
>> says this? I read it differently (page 10 of I2C 2.1 specification,
>> section 7.2: Acknowledge):
>>
>> "Usually, a receiver which has been addressed is obliged to
>> generate an acknowledge after each byte has been
>> received, except when the message starts with a CBUS
>> address."
>>
>> "If a master-receiver is involved in a transfer, it must signal
>> the end of data to the slave-transmitter by not generating
>> an acknowledge on the last byte that was clocked out of
>> the slave. The slave-transmitter must release the data line
>> to allow the master to generate a STOP or repeated
>> START condition."
>>
>> So, a master-receiver must nack the last byte, but a slave-receiver must
>> not. So your slave device is misbehaving - or you are actually trying
>> to write more bytes to it than it can handle.
>>
>
> Refer to fig.11 of specification 2.1.
> But I think that I was wrong. I agree with your opinion.
>
>>> (i have see the possibility to set the I2C_M_IGNORE_NAK but ignore all
>>> NAK and isn't right!)
>>
>> This should indeed be avoided unless you really have to use it.
>>
>>> There is a solution or I have to modify the code?
>>
>> First ensure that you are sending the right number of bytes to the
>> device, with the correct sequence. If you think you're really doing the
>> right think, get in touch with the vendor of the slave device and ask
>> them why their device misbehaves.
>>
>
> I'm in touch with vendor, I'm waiting for his reply.
>
> Thank you
> Michele
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-- 
Michele Da Rold
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