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AD9577 I2C problem

Question asked by al_smith on Jul 31, 2015
Latest reply on Nov 9, 2015 by neilw

Hi Guys,

 

I have a custom board with the AD9577 clock generator on it. I am having problems writing/reading I2C. I have it hooked up to a procesor running embedded linux driver, which reads back the following table of values, so the device appears to be talking:

 

     0 1  2  3  4  5  6  7  8  9  a b  c  d  e  f    0123456789abcdef

00: 00 40 10 00 00 00 00 00 00 40 10 00 00 00 00 00    .@?......@?.....

10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80    ...............?

30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00    ..............?.

40: 00 00 00 04 00 00 ae 16 00 00 00 00 00 00 00 00    ...?..??........

50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................


With the input REFCLK clock enabled the I2C output changes and I get the first line of registers as follows:


     0 1  2  3  4  5  6  7  8  9  a b  c  d  e  f    0123456789abcdef

00: 00 6F 3F 00 00 00 00 00 00 78 3F 00 00 00 00 00    .@?......@?.....


However, I can't seem to write to the device and read back any changes, so I'm wondering whether the I2C is working correctly. Is what I am seeing correct?


I have analysed the I2C bus with an advanced 'scope and get the following, which is consistent with the linux driver. Am I missing something? I can't find a complete table of registers for the device which may help.


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