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November 2, 2010 AT 4:51 pm

NEW PRODUCT – i2c / SPI character LCD backpack

I2Cspilcdbackpacklcd Lrg

I2Cspilcdbackpack Lrg

NEW PRODUCT – i2c / SPI character LCD backpack. LCD backpacks reduce the number of pins needed to connect to an LCD. LCDs are a fun and easy way to have your microcontroller project talk back to you. Character LCDs are common, and easy to get, available in tons of colors and sizes. (or similar microcontroller) but find that the number of pins necessary to control the LCD can be restrictive, especially with ambitious projects. We wanted to make a ‘backpack’ (add-on circuit) that would reduce the number of pins without a lot of expense.

By using simple i2c and SPI input/output expanders we have reduced the number of pins (only 2 pins are needed for i2c) while still making it easy to interface with the LCD. For Arduino users, we provide a easy-to-use library that is backwards compatible with projects using the ‘6 pin’ wiring.

This backpack will work with any ‘standard’ character LCD, from 8×1 to 40×4 sizes! As long as they have a 16-pin single-line connection header at the top. We carry a few LCDs that work great.

For advanced users, this project can be used for general purpose I/O expansion, the MCP23008 has 8 i/o pins (7 are connected) with optional pull-ups, the SPI 74HC595 has 7 connected outputs.

For a detailed tutorial on usage, including an Arduino library, wiring diagrams, and files, please visit the product page

In stock and shipping now from the Adafruit store!


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8 Comments

  1. Great stuff! There will be a few of these in my next order!

  2. Nice product. I was considering making something similar (PIC16xxx and using the uart to communicate to the external circuit)
    I am gonna skip making one now that there is a better option available. Thank you!

  3. As usual, awesome stuff from adafruit!

  4. Here I am making a LCD-I2C board for my launchpad http://www.43oh.com/forum/viewtopic.php?f=10&t=164 and you just have to go and make one too. Go fig. (P.s. great minds, yadda yadda yadda :D)

    Suggestion for next revision, why not add a smd low profile dip switch/jumper, or a right angle 2 pin smd header so that a standard jumper can select between i2c and spi mode? This would make it more versatile. Great idea with the weak pulldowns on the i2c address lines. I’m going to have to borrow that one.

  5. Here I am making a LCD-I2C board for my launchpad http://www.43oh.com/forum/viewtopic.php?f=10&t=164 and you just have to go and make one too. Go fig. (P.s. great minds, yadda yadda yadda :D)

    Suggestion for next revision, why not add a smd low profile dip switch/jumper, or a right angle 2 pin smd header so that a standard jumper can select between i2c and spi mode? This would make it more versatile. Great idea with the weak pulldowns on the i2c address lines. I’m going to have to borrow that one.

  6. cde, we’ll check it out… we wanted to hit the $10 price point but we think this is a good start!

  7. I like the idea of a switch or jumper as cde mentions, but it’s only needed if you’re reusing the device. Once integrated you won’t need the extra component.

    So keep the costs down and perhaps a rev b would have a modified PCB with a place for through hole header or smd dip switch pads. This way if someone was using it as a prototype component they could add the header+jumper or switch. For a prototype rig the user might consider female header on the backpack and male header on their lcd.

  8. so then I look at the photo and remember the address jumpers, so maybe 4 position smd dip switch? but space is tight…

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