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i2c decoding problem

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i2c decoding problem

Postby doekle » Sun Sep 26, 2010 8:13 pm

I tried to use the I2C serial decoding tool, but without any success. The decoder does not seem to recognize a start condition the way it should. What am I doing wrong? Attached a screenshot: clearly the SDA drops before the SCL, and no start condition is decoded, neither is the data properly decoded. I have tried numerous things, even tried to exchange SCL and SDA.

Hope you can help me out.
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Re: i2c decoding problem

Postby ziko » Mon Sep 27, 2010 3:31 pm

You need more packets really, try using a longer timebase. The software needs to see at lease one start and one stop bit.
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Re: i2c decoding problem

Postby doekle » Wed Sep 29, 2010 9:21 am

ziko wrote:You need more packets really, try using a longer timebase. The software needs to see at lease one start and one stop bit.


So I will always miss the packet I am interested in? My Picoscope 2205 buffer is only 16kB, not long enough to store data for seconds. I will try whether this is indeed the case, because I cannot believe it...
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Re: i2c decoding problem

Postby ziko » Fri Oct 08, 2010 1:53 pm

Hi,

The CAN bus decoding is not limited in the software, it is the hardware that will dictate how long you wish to look at a signal for.

Have you tried increasing the timebase to see if it has an effect?

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Re: i2c decoding problem

Postby doekle » Sun Jan 02, 2011 8:11 pm

I have tried with different time base settings and so on, even tried the inverse of he wave forms. The software seems not to recognize the start and stop conditions properly. What I have noticed is that it recognizes a rising clk while data is low as a stop condition, it should be a rising data while clk is high. Similar story with the start sequence. I have attached a measurement file, please tell me what I am doing wrong.
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Re: i2c decoding problem

Postby ziko » Wed Jan 12, 2011 10:14 am

Hi have you tried the latest bet software?

http://labs.picotech.com/#psw6

Let me know how you get on.

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Re: i2c decoding problem

Postby doekle » Tue Jan 18, 2011 5:38 pm

I have loaded the file as posted in my previous post into the new version (6.5.54) and it immediately recognizes the start codes! great! I will try with some live data later and keep you updated. Thanks.
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