[51] i2c : PCF8575 Read and Write function roblem

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chiart

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Hi,

I'm connecting the PCF8575 with the P89C51RD2 microcontroller. I've managed to communicate with the PCF8575 chip using the i2c lines. However, i'm facing a problem with the read and write function with this chip.

Meaning that, I have no problem in reading the data, also no problem in sending the data, but I'm having problem to read back the data I've already sent.

Is it possible to do read back the data that we've already sent using this chip?

Any help highly appreciated.

Thanks.
 

As long as the port pins are open, you'll read back the previously written data. If a pin is shorted to ground, you read '0' independent of the previous written pin state.
 

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