kicad mcp23s17 schematic

[JoeD.]

Hi
I am working on a MIDI controller project. This is my first Kicad schematic, I'm setting up multiple mcp23s17s to a Teensy 4.1 to expand the pin number for encoders. Would anybody out there mind taking a look at the schematic and seeing if it is correct so far. Are there any changes I should make? Im hoping to get a PCB board made soon. Thanks in advance!

 

[skpang]

You need to add a decoupling capacitor, say 100nF close to pin 9 of U2.

 

[BillFM]

mcp23s17s is being powered by 3.3V.
What voltage is Vcc ?

 

[JoeD.]

Thanks SK Pang! The voltage is 3.3

 

[BillFM]

Are you using A2/A1/A0 for each MCP23S17 ? Don't forget to change the settings for each MCP23S17 chip.
Or, are you using a separate CS for each MCP23S17 chip ? If so, don't worry about previous sentence.

 

[JoeD.]

Yes I'm using separate CS for each MCP23S17 chips

 

[BillFM]

Sounds good!

You might want to review some of the pins that have been assigned to SD cards, Audio Adaptor, and avoid using these in your design (best to avoid conflicts before pcb is manufactured).
T 4.1 + SD + FLASH + Audio pins

 

[JoeD.]

is this .1uf decoupling capacitor on pin 9 correct?

 

[JoeD.]

I'm a little confused on how the decoupling capacitor should be placed. It's supposed to connect the VSS and VDD, right?

 

[MarkT]

Straight from Vdd to the groundplane. Vss is ground.

 

[JoeD.]

So would it look like this? On the actual chip the VDD and VSS are right next to each other to the capacitor could be close to the pin, but this schematic doesn't feel right.

 

[MarkT]

A schematic is not a layout, in schematics people often put the decoupling caps in a separate section away from the action to avoid clutter.