Is this configuration of MCP23S17 right?

Hi,
I want to use several GPIOs to control 10+ LED, so I selected MCP23S17 IC.
I wan to use 2 GPIO to simulate SPI interface to control MCP23S17 IC.
I am not sure about my config, pls comment, thanks.
1. _CS link to GND is right? In code, if it is needed to set _CS to 1 or 0?
2. The STM32 only set MCP23S17, and doen't need feedback from MCP23S17, so SO in NC, OK?
3. Do SCK and SI need 10K pullup to +5V or +3.3V?
4. I saw some design leave INTA and INTB NC, do these int need config by SW ? Or my design just link them to GND, right?

Hi,

First I was confused, because you talk about GP pins used as SPI...and you talk only about the MCPxxx, which has GP pins.
But later I realised you meant GP of an unknown microcontroller.

Btw: there are lots of solutions that use HC595. Simple, good available and cheap.

1) CS = LOW?
--> why don't you read the datasheet? It clearely says:
* The SPI xxx operation is started by lowering CS.
* The sequence ends by the raising of CS.

2) so SO in NC, OK?
Outputs my be left open, when not used.
But the SI of the microcontroller
--> general rule: Don't let any unused input floating. Either pull it to valid HIGH, or valid LOW

3) Do SCK and SI need 10K pullup to +5V or +3.3V?
--> both should be push pull (totem pole) outputs. No need for pulling them with resistors..

4) INTA, INTB
--> Why don't you read the datasheet? It clearely says:
* Interrupt output for PORTx. Can be configured as active-high, active-low or open-drain.

Klaus

Hi, Klaus,
Thanks.
I am sorry not to make the GPIOs clear, which are from a STM32 output.
About INTA/B, although the datasheet said they can be high/low/open, I want to clarify in my circuit their status.
Soon I will paste the circuit using HC595, which should be a good idea.
Best,
Tony Liu

Hi, ALL
Attachment is the HC595 circuit for I/O expander.
Welcome to comment.