Digital pin internal pullup query

In my attempts to establish communication between a BW16 and Wiz5550 ethernet chip I found that the Wiz5550 module that I am using has a floating CS/SS line. MOSI, MISO and CLK lines are also floating.

A circuit copied from the wiz5500 forum, showing pull up on the CS/SS line, is copied below.

My question is whether all the above pins on the BW16, dedicated for use in SPI, have internal pullup resistors? I would like to use arduino instruction to enable pull ups on all these pins, particularly the CS/SS pin. Subsequently I can add a 10K resistor externally. For now I want to use internal pull up

Am I on the right track or there no real need for it.

Hi @azhaque,

It is good to add in the internal pull up resistor. Connecting external pull up resistor would be easy too. You can try using this line of code to do internal pullup.

pinMode(_pin, INPUT_PULLUP);

This may not work if that particular pin do not have internal pull up resistor.

Thank you.


I have added an external pullup resistor of 6.8K.
The result was that now a value of the VERSIONR is being returned. However the value returned is 1, while the datasheet says it should be 4.

I have no way of knowing whether the ‘1’ returned is wrong which would mean software (or hardware) bug. Of course the presumtion is that the datasheet is correct. But then there is no means to test it using the BW16.

Will try to use the same code on an ESP32 to see the result.