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IO-EXPANDER-EVM: TCA9535

Alan Lawrenson
Prodigy 40 points
Part Number: IO-EXPANDER-EVM
Other Parts Discussed in Thread: TCA9535

Hi ,

Is is possible to use the IO-EXPANDER-EVM: I2C and SMBus IO Expander Evaluation Module plus GUI to drive say 2 or 3 other expanders on seperate PCB. The expanders would all be the same type TCA9535 . I would hardwire the SDA/SCL/INT , supply and ground connection lines to the other expanders and program the relevant ports. The external expanders all have different address lines set in hardware.

I checked the GUI and it does not appear to have the facility to set the expander address is this correct?

Thanks,

Alan 

  • 0
    TI__Guru 72621 points
    Hey Alan,

    "Is is possible to use the IO-EXPANDER-EVM: I2C and SMBus IO Expander Evaluation Module plus GUI to drive say 2 or 3 other expanders on seperate PCB."

    -It is "technically" possible in terms of hardware however with multiple IO expanders you will need to modify the other boards slightly to change the address pins (a0,a1,a2) to ensure there isn't address conflicts. The schematic on page 12 of the EVM user guide shows how you may want to approach this. Pins 2, 3, and 21 are the address pins for the TCA9535 though the EVM will tell you those are VCCI, and reset for pins 2 and 3. You would need to remove R8 and use the pad furthest from power rail to pull that side to GND. Then on another board you would probably want to do the same approach with R15.

    The only road block I see in this would be the GUI which I've only used once before but from my experience, it does not allow for me to choose an address to send to. So from your hardware configuration you are set to communicate to 3 I2C devices but from a software perspective you are not....

    "I checked the GUI and it does not appear to have the facility to set the expander address is this correct?"
    -Unfortunately, it looks like that is the case. It may be easier to use a microcontroller with an I2C library and try interfacing directly through that than through our GUI (through the MSP430 launchpad).

    -Bobby