Hello, I'm new to arduino and I got an IO expander chip that uses SPI to communicate with the arduino but I am having a hard time making things work. I triple checked my hardware connections and there seems to be no fault. I followed the steps in the documentation for arduino SPI and came up with t…

You state: "I got an IO expander chip that uses SPI to communicate with the arduino" That tells me you have one of many thousand different devices. My eyes are not what they need to be and I cannot see what you have even with my glasses. Posting a Schematic, not a frizzy thing with technical lin…

Hello I am using an arduino Uno R3 which looks like this one: https://hetpro-store.com/dccduino-smt-arduino-uno-r3-r2-compatible/ As for the schematic of the wiring, I drew it by hand and it's shown below: [Schematic] Thanks!

Hi it's the M66006P by Mitsubishi; I posted its name at the end of the post. Also, I added a schematic now apologies for the confusion :slight_smile:

Does the chip have built-in pull-down resistors? If not, you will need pull-down resistors (10k between chip input pin and Ground) to keep the pins from floating when they aren't connected to +5v.

Okay I will try that tomorrow once I get the 10k Ohms resistors, I hope this is the problem, thanks!!

The MCP23S17 is a 16 bit SPI port expander that has built in pullup resistors that can be enabled for each input. The MCP23S17 also has pin change interrupt capability that can be handy for reading switches.

Unfortunately it's not available in my country. Ideally, I would want something with as much GPIOs as possible but the M66006P is the closest I'll get :frowning:

[image] thesuicidalpenguin: Unfortunately it’s not available in my country That truly is a bummer. I use the I2C equivalent of the MCP23S17, the MCP23017 and really like them for adding GPIO to my projects.

[image] thesuicidalpenguin: SPI.transfer16 Is that a real command? I would normally do two SPI.transfer() with a byte in each.

Using SPI for IO Expander

Projects Networking, Protocols, and Devices

groundFungus April 28, 2021, 2:35pm 2

I can post a data sheet for the M66006P
.

Which Arduino board are you using?

Please post a schematic of your wiring.

Read the forum guidelines to see how to properly post code.

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Using SPI for IO Expander

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