[En-Nut-Discussion] TWI aka I2C, not getting an ACK back? - SOLVED

[Douglas Pearless]

OK!

I noticed that I am getting tiny glitches (around 10ns) on the SDA line 
on the end of each 8th bit of the SCK, before the 9th bit (ACK), maybe 
the low resistance has something to do with that?  Perhaps a 0u1 bypass 
capacitor to ground is required on SCK and SDA??

Noting the SCK and SDA lines would be about 2cm from the SDA and SCK 
connector lines on the Ethernut 2

Cheers Douglas

Alexander Baranov wrote:

>I'd recommend 4.7k rather than 2.2k.
>Alexander
>----- Original Message ----- 
>From: "Douglas Pearless" <Douglas.Pearless at pearless.co.nz>
>To: "Ethernut User Chat (English)" <en-nut-discussion at egnite.de>
>Sent: Thursday, March 17, 2005 4:16 AM
>Subject: Re: [En-Nut-Discussion] TWI aka I2C, not getting an ACK back? -
>SOLVED
>
>
>  
>
>>Hi Harald,
>>
>>Thanks for the assistance.
>>
>>It turned out that the TwMasterTransact routine, when you pass the
>>address of an array for the transmit buffer, it starts the 'read' from
>>the data[1] not data[0], so it was skipping the register address of the
>>DS1337 which was in the zeroth position (data[0])
>>
>>When I figured that out, and corected my code, it then worked perfectly!
>>
>>Rather bizzare, but then I am no C expert!
>>
>>Cheers DOuglas
>>
>>Douglas Pearless wrote:
>>
>>    
>>
>>>There are only two 2k2 pull ups on SDA and SCK to +5v and the DS1337.
>>>There are no other wires or connections!
>>>
>>>Cheers Douglas
>>>
>>>Harald Kipp wrote:
>>>
>>>      
>>>
>>>>Hi Douglas,
>>>>
>>>>At 16:30 16.03.2005 +1300, you wrote:
>>>>
>>>>        
>>>>
>>>>>   rc = writeRTC(sla,0x0E,dataRTC,2); //on the i2c bus I get
>>>>>"<start> 110100000 <SDA goes high>  000000000  000000000
>>>>>000000000<stop>
>>>>>//where did the 0x0E go which should have been immediately after
>>>>><SDA goes high>
>>>>>//I checked the wrteRTC routine and it does pass 0x0E 0x00 0x00 in
>>>>>the 'data field to TwMasterTransact
>>>>>          
>>>>>
>>>>
>>>>What about hardware? You are aware, that I2C is open
>>>>drain? Did you add pull-ups? Anything else connected,
>>>>which may drive the bus low?
>>>>
>>>>Harald
>>>>
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