Hi everyone, I have been playing around with keypads recently and became frustrated that I didn’t have enough pins to use the keypad with any other equipment. To fix this, I made Keypad-I2C, a library which allows anyone to connect a keypad using an I2C port expander. Currently, the only chips sup…

That’s awesome! Thank you so much for the contribution! What are you building?

@will The reason I built the library was for a controller for an neopixel shield. I have the keypad and a screen hooked up to my Photon and am using it to control an RGB on another Photon. I haven’t implemented the neopixel shield yet because I can’t seem to find a Particle library that works with t…

Have you had a look at this? [image] Adafruit Neopixel Library [PORTED] Libraries ###Just updated the NeoPixel library to support the RGBW NeoPixels grin Important: If you have an old app in Build that you are migrating to a Photon, P1, Electron or Core, please remove th…

Thank you for showing me, I hadn’t seen that! It’s been a busy week. I guess I’ll finish the project this weekend then!

I have a project I want to add a keyboard and LCD to and I would like to use this library so I can take advantage of the I2C bus. I have been looking at the code and the MCP23017 datasheet, but could use some help. As a first step I was trying to use the code from the example in the library, whic…

@jariding , it looks like the library calls the begin() function for MCP23017 which uses the default I2C address for the device. Unless you modify the library, you won’t be able to set the address.

@jariding I am working on a modification to let users define the address. It builds but I don’t have my board with me to test it so I won’t publish it just yet. You can try replacing the header and source files with the following though and see if it helps. Keypad_I2C.h: /* || || @file Keypad_I2C.…

Thanks to both of you for your replies. I don’t necessarily need to modify the address, I just assumed I needed to set it to something on the MCP23017 and put it in the code somewhere. I’m not sure what the default address is, however. Is it 0x20? This would work fine for me since the LCD is 0x27…

In response to your first question, yes the default address is 0x20. The numbering of the row and column pins corresponds to the numbered pins on the MCP23017 so the row pins as you’ve defined them would be GPB0-3 and the columns would be GPB4-7. The mapping should be in order but I don’t remember i…

Okay @esimkowitz thanks for the information and thanks for creating the library. I was able to get the simple example program working. I had forgot to connect the two ground buses on my breadboard and wasn’t addressing the I2C chip as a result. This was causing me to get some random characters at…

Connecting a keypad over I2C

Firmware Libraries

ScruffR June 15, 2016, 7:58pm 4

Have you had a look at this?

@BDub has just recently added RGBW support

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Connecting a keypad over I2C

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