TCA9543A: Interfacing Questions

Hey Rocketman46 (cool name),

"I am about to use the TCA9543A for the first time to read 2 slave I2C sensors with the same address."

I actually wrote a step by step guide on how to use a switch on e2e, this may be helpful for reference:

"1) Can I use A0 and A1 to select between slave devices?

-No, this is not how the address pins work. You need to think of the TCA9543A as an I2C slave. It needs to have a unique address and therefore the A0 and A1 pins help by giving the slave more options to an address (with A0 and A1 this gives 4 extra possible addresses it can have thus you can use 4 of these switches on the same I2C line if needed.)

"Is its possible to connect the 2 pins to micro I/O pins to activate each channel, or must they be tied to VCC or GND".

-No, Please see above.

"2) Both of the slave devices do not use interrupts.  Therefore do I tie these unused pins to VCC?"

Yes, but use a pull up resistor (size on this doesn't matter but a normal value used in the industry is 4.7k or 10k).

BTW there is a section in the datasheet which point out what to do with some pins:

"3) The interrupt pin on the master side is not used, so do i tie this pin using a pull-up to VCC?"

-This isn't 100% required as this pin is an output put if you are want to follow general best practice then use a pull up resistor to Vcc (Size on this one does matter if you were using it though 4.7k or 10k would be good values).

"4) I am hoping to use the TCA9543A  by selecting A0 using a micro I/O pin, then read and write data, select reset, then select A1 using a micro I/O pin, then read and write data.  Is this the correct process to read data?"

-No. What you are talking about is an actual MUX and this is not the same as an I2C MUX, an I2C MUX is controlled via I2C communication on SDA/SCL. A MUX is controlled via a selector pin (only one pin would be needed in a MUX for this because two outputs means only 1 bit is required). The advantage on an I2C MUX is it does not require additional GPIO pins from a processor.

Please refer to the "how to use a switch" post in the beginning of this post. Also the datasheet also discusses how to use this device in section 9.5

"5) Have I missed any configuration steps?"

Please refer to everything above.

Thanks,

-Bobby