PCA9534A: register read and wrote is not the same

Brian Li

Expert 7535 points

Part Number: PCA9534A

Hi team,

My customer is using our PCA9534A，and they find when they config 0x03，the value read and wrote is not the same.

They also check the input register 0x00，they find the value also can't match the input voltage.

Could you please help check the cause & if they need to config some register before use?

Thanks,

Brian

6 months ago

0 Clemens Ladisch 6 months ago

Guru 244370 points

Please show the code, and an oscilloscope trace of the write and read.

0 Tyler Townsend 6 months ago

TI__Mastermind 23943 points

Hi Brian,

As Clemens suggested, I think we need a little more information before we can diagnose the issue. Software/code and o-scope captures of the I2C bus would help us to determine if the device is being addressed properly.

Regards,

Tyler

0 Brian Li 6 months ago in reply to Tyler Townsend

TI__Expert 7535 points

Thanks Tyler & Clemens,

Here is the code and the sch:

IO拓展芯片运行异常排查资料.rar

Please help check the cause.

Thanks,

Brian

0 Clemens Ladisch 6 months ago in reply to Brian Li

Guru 244370 points

The schematic does not show any pull-up resistors on the SCL/SDA lines.

Please show an oscilloscope trace of the write and read.

0 BOBBY 6 months ago in reply to Brian Li

TI__Mastermind 49410 points

Hi Brian,

I verified the schematic looks okay.

As Clemens and Tyler have pointed out, it would be useful if you can provide scopeshots of the issue you are seeing.

-Bobby

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PCA9534A: register read and wrote is not the same