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TCA9535: TCA9535xxxxx

Part Number: TCA9535
Other Parts Discussed in Thread: PCA9535

I understand TCA9535 or PCA9535 interface is I2C and Require external pull-up resistor on SCL and SDA lines

We have a SPI-GPIO expander on board and it's QFC24. The big issue right now is the lead time is way too long (26+ weeks). 

Our SPI-GPIO expander is kind of "pin compatible" with  TCA9535/PCA9535 other than I2C vs. SPI.

Where I2C and its A[2:0] are on SPI + RESET pins of our SPI-GPIO expander

#1

Dose TI has SPI-GPIO expenader with pin compatible to TCA9535 or PCA9535? 

#2

The SPI interface is connected to FPGA point-to-point without external pull-up on our board.

Again, I understand TCA9535 or PCA9535 interface is I2C and Require external pull-up resistor on SCL and SDA lines 

I like to check could TCA9535 or PCA9535 be used as a drop-in in our case? In which the connection is point-to-point directly to the FPGA.

Hope to hear from you ASAP. Thank you.

  • There is no SPI expander.

    The built-in pull-up resistors of the FPGA might work for I²C if you reduce the speed.

  • Thanks for the help Clemens!

    New2day,

    As Clemens said, we don't have specific SPI to GPIO expanders at the moment, just I2C. I've notified our I2C expert to comment further on this thread if necessary.

    Regards,

    Eric Hackett 

  • Thank you all for prompt response. It'll be great if I can get further comments. Thank you.

  • Dose TI has SPI-GPIO expenader with pin compatible to TCA9535 or PCA9535? 

    No, TI does not currently have SPI IO expanders in the portfolio.

    I like to check could TCA9535 or PCA9535 be used as a drop-in in our case?

    Does the FPGA have an I2C module/hardware built into the pins connected to our SDA/SCL pins? If not, then you would need to bit bang the pins to generate an I2C signal. You can't directly drive the SDA/SCL lines of an I2C device with MOSI/MISO.

    -Bobby

  • About FPGA, there will be code modification by implementing a I2C controller module to replace existing SPI one. 

    I like to check if it fine without external pull-up resistors that I2C normally has for this "drop-in" application (point-to-point). Thank you.

  • I2C requires an external pull up to generate the high signal, you can use push pull on the SCL line but the SDA line should have an external pull up or you would need to be able to enable an internal pull up on the FPGA. 

    If you make the FPGA push pull on SDA, you will have contention issues during the SDA hand off phase and will only be able to send low signals when receiving since there is no high signal that can be transmitted due to I2C's open drain architecture (our 9535 will not generate high levels for the FPGA to receive).

    -Bobby