Too many pins needed

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smblackledge
 
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Joined: Thu Mar 13, 2014 5:08 pm

Too many pins needed

Post by smblackledge »

I've got a 20x4 lcd display and a 4-digit, 7-segment display. Both of these use incredible numbers of pins, something that my UNO R3 doesn't have an abundance of. I'm going to get the backpack for the display which cuts that one down from 12 to 6 (I think) pins. I don't think I have enough pins for the 4-digit, 7-segment display, though, not to mention anything else (such as a speaker, push button, etc.). Besides get a Mega, does anyone have suggestions?

Thanks,
Scott

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adafruit_support_mike
 
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Re: Too many pins needed

Post by adafruit_support_mike »

It sounds like you need an I2C port expander:

http://www.adafruit.com/products/593 - MCP23008 (8 channels)
http://www.adafruit.com/products/732 - MCP23017 (16 channels)

Both chips communicate with your Arduino through the I2C bus, so they only use two pins. They have pins that let you set the chip's address, so you can put up to 8 of them on the same bus. Each GPIO pin on the MCP23* can be configured as a digital input or output, and since we use them by the pound in our own products, we have complete code libraries for working with them:

https://github.com/adafruit/Adafruit-MCP23008-library
https://github.com/adafruit/Adafruit-MC ... no-Library

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