PCA9698 I/O Expander unable to write the data

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PCA9698 I/O Expander unable to write the data

Contributor I

Hi All,

I am trying to write and read the data to and from the PCA9698 I/O Expander (as a slave device) but device gives the NACK when I am writing and reading anything to/from it.

Can any tell me, How can I read and Write the data from the I/O Expander PCA9698?

Does anyone has built a code to read and write the Data to/from the I/O port which can help me?

I have used Slave Address 4Eh by applying the VDD to all AD0 to AD1 Pins.

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NXP TechSupport
NXP TechSupport

Hi Karan,

If you have a logic analyzer or an oscilloscope, could you please post here the picture illustrating the I2C traffic?

Have you tried any other I2C slave addresses according to Table 12 of the datasheet? Note that 0x4E corresponds to AD2 = AD1 = AD0 = Vdd and it is the 7-bit address which translates to 0x9C (0x4E << 1) for a write and 0x9D ([0x4E << 1] | 0x01) for a read.

I hope it helps.

Best regards,


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Contributor I

Hello Tomas-

I know this is an old post but this is basically the exact problem I'm having, where it appears the PCA9698 is not responding to my addressing input.

I've uploaded some screen/shot info to this imgur link if you can take a look:

Imgur: The magic of the Internet 

Basically, I interpret the issue as the PCA9698 is not ack-ing, as in not drawing the SDA line low during the 9th clock cycle in that oscope capture.

Please let me know if there is a better (faster) way yo reach you or communicate as the project this is intended for is at risk schedule wise and we intend to be purchasing many more of these chips assuming I can be successful here.



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