I’m looking to start a project (an internet-connected, openHAB enabled busy board for my kids!) and my plans involve significantly more IO pins than the photon has. I have been looking at the PCF8574 as a means to connect a bunch of switches to the setup. I have found some Arduino tutorials for the…

My libraries support multiple devices/addresses: MCP23008-RK MCP23017-RK They’re in the community libraries as well, but the documentation is at the links above.

Have you got a link to the Arduino library to look at? But with enhanced Arduino compatibility of system 0.6.2 you could just try to build the code and see if it compiles.

SparkFun has a retired break out board that you might be able to base some code from (firmware/library) for the chip you specify. [image] sparkfun/I2C_Expander_Breakout-PCF8575 I2C_Expander_Breakout-PCF8575 - SparkFun I2C Expander Breakout - PCF8575 Otherwise, t…

I use the MCP23008 I2C GPIO expander in my I2C tutorial, see the “GPIO Expanders” section. There’s a link to the Particle library there as well. [image] rickkas7/particle-i2c-tutorial particle-i2c-tutorial - Using the I2C bus with Particle devices

Thanks for the suggestions! I’ve had a busy weekend and haven’t had a chance to dig in. I originally wanted to go with the PCF8574 because I already had a few of them, but it’s looking like it might be easier to just run with the MCP230xx.

@ScruffR I tried a few Arduino tutorials for the PFC8574 but couldn’t get any of them to compile… probably problems with the libraries; I decided to go the MCP230xxx route. @rickkas7 Someday, I’ll learn to check the code before I buy the parts… I ended up buying some MCP23017 chips instead of the M…

@rickkas7 Disregard, I got the MCP23017 working with an Adafruit library I found in the IDE. Not sure how I missed it the first time… Thanks for the tutorial; even though I used a different library it’s the best explanation I’ve ever seen for using i2c in a variety of ways! Now the fun can begin in…

I did make a MCP23017-RK library that has the same API as the MCP23008-RK but has support for all 16 GPIO pins. [image] rickkas7/MCP23017-RK MCP23017-RK - Particle driver for the MCP23017 GPIO Expander There’s no reason to switch if you have it working with the …

@rickkas7 This is great… thanks for your efforts. One quick question - I’m looking at hooking up several MCP23017 chips, along with some PCA9685 PWM expanders. Should I use pullup resistors near every device, or just one set close to the Particle?

One pull-up resistor (2.2K to 10K) on each of SDA and SCL, ideally near the Photon/Electron, though you can put it anywhere. But only one set, not one per MCP230xx.

@rickkas7 Sounds good. Thanks for the clarification. I’m developing a breakout board for the MCP23017 and wanted to get this clear.

PCF8574 IO Expander Board - Tutorial/example requested

Hardware

dome May 31, 2017, 10:06am 12

I’m making great progress, though some may say I’m going a bit overboard.

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PCF8574 IO Expander Board - Tutorial/example requested

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