LCP1778 I2C timing question

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LCP1778 I2C timing question

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amandalin
Contributor III

LPC1788 I2C1 output can not meet the requirements of PCA9713'tHD;DAT timing,PCA9713'tHD;DAT timing need less 300ns,can you help me confirm LPC1788 solve probelm with software?or have others method?

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Hui_Ma
NXP TechSupport
NXP TechSupport

Hi

I had done a test with LPC1788 Developer board using I2C1 with on board EEPROM.

I measured the SCL signal with SDA signal at falling edge with scope:

pastedImage_1.png

The I2C1_SDA signal falling edge is after I2C1_SCL signal falling edge, which the I2C communication as expected.

And the LPC1788 datasheet I2C-bus Dynamic characteristic also with below description:

pastedImage_2.png

pastedImage_3.png

My understanding about note 4 is to avoid the SCL signal with very slow falling edge and make sure SDA signal still hold during SCL falling edge. The SDA signal hold time was internally provided.

The LPC1788 I2C module should work with PCA9713 without any problem.


Wish it helps.

Have a great day,
Ma Hui
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amandalin
Contributor III

Dear Hui_Ma:

      Ok,Thanks for you reply.

      But customer have a question about PCA9513 in this case,when test I2C  sequence(SDA and SCL sequence),he find I2C output sequence(tHD;DAT<0nS),can you help how do sovle problem

     The attached is tHD;DAT waveform of I2C output,pls check it

pastedImage_2.png

     Thanks

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Hui_Ma
NXP TechSupport
NXP TechSupport

Hi Amanda,

First of all, sorry for the later reply.

I checked attached PCA9513A schematics, could you tell us the above scope measurement point at SCLIN/SDAIN or at SCLOUT/SDAOUT pins?

Have you tested to remove the PCA9513A chip and measure the LPC1788 I2C module output signal with 4.7K ohm pull-up?


Have a great day,
Ma Hui

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amandalin
Contributor III

Hi hui_ma:

    sorry ,i forget tell you that customer test piont is 30%CLK to 70%DATA ,times is -14ns,

    Customer remove the PCA9513A chip ,LPC1788 I2C output is ok

    Customer use LPC1788+PCA9513A,LPC1788 I2C output(PCA9513A input) is ok,but PCA9513A I2C time is <0ns(-14ns)

    Do you have give your mobile phone or telephone?

    Application :Server

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Hui_Ma
NXP TechSupport
NXP TechSupport

Hi Amanda,

So, the PCA9513A output I2C time with above mentioned issue, right?

For the private info protection, if you need one to one service, I would recommend you to submit a case in our service system.

Please following below link to submit a service request to us, thank you.

https://community.nxp.com/docs/DOC-329745 


Have a great day,
Ma Hui

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amandalin
Contributor III

ok ,i want to discuss about this question


the PCA9513A output I2C time with above mentioned issue, right?

YES,That's the problem,can you help confirm this question how effect about system?


if customer use LPC1788+PCA9513A,Whether there is an impact?


thanks

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Hui_Ma
NXP TechSupport
NXP TechSupport

Hi Amanda,

Could you try to modify PCA9513 external circuit related capacitor and resistor value below?

C83 from 0.1uF to 0.01uF;

R252 & R254 from 4.7Kohm to 10Kohm.

Please let us know if the issue is still there.


Have a great day,
Ma Hui

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amandalin
Contributor III

  Dear Ma hui:

        customer change C83 from 0.1uF to 0.01uF,and R252 &R254 from 4.7K to 10K,still no help

do you have others solution?

thanks

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Hui_Ma
NXP TechSupport
NXP TechSupport

Hi Amanda,

Could you check customer measure above I2C signal from PCA9513 with I2C smart card device or not?

And if customer slow down the I2C baud rate, any modification with that signal?

Another question is how many PCA9513A chip with that issue?

Thank you for the help.


Have a great day,
Ma Hui

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amandalin
Contributor III

Dear Hui Ma:

     ok ,i will check question,thanks

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amandalin
Contributor III

  Ok,i will contact RD,pls he change C82 cap to 0.01uF,if have conclusion ,i will tell you

thanks

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