New board for I2C LCD Backpack

Anyone who has seen my unfinished post about the I2C LCD backpack probably thinks that is a long time forgotton project. Not really, I just wanted to take it a step farther than I had and didn’t. That is until now. I just discovered a very reasonable prototype PCB manufacturer. Where for a board that is less than 2″ x 2″, you can get ten boards for less than $20 shipped. Yes, less than $2 per board shipped. When I found that, I couldn’t pass it up. So, I finalized my board design and ordered them.

These boards are purchased from and shipped from China so I was expecting a long delay. I must say though, I was pleasantly surprised. I placed my order on February 4th and sent my files to them via email. I got a response from them that they had sent my designs to the fabricator on the 5th. On the 14th, they flagged my order as “Delivered” (Really meant shipped). On the 20th, Hong Kong tracking said it left Hong Kong. And on the 27th, they were at my home in N/W Indiana. Pretty good for a start to finish.

The boards look great too. Here is a shot of the front and back of the board.

Blank board top

IC side of board

Bottom of board

Back side

As you can see, the boards look good.

I did have one down side.  When I designed my backpack, I used a port expander I had sourced from Maxim.  It was a MAX7318AWG.  Since then, this part doesn’t seem to be available anywhere.  While there is a suitable pin for pin alternative, the MAX7311AWG, they are a bit pricey where I did find them.  Oh well, at least the boards will be usable :D.

I had on hand all the components to build the board except for the SMD Potentiomenter for contrast.  I know however, as long as the contrast line is biased to ground with a 1K resistor that the contrast works.  So, I just installed a 1/8W 1K resistor in place of the pot.

Here is the end product.

Board Top

IC side




Solder Jumpers for Pullups (Above R2 & R3)

Contrast Resistor

Contrast Resistor (1K) Tied from GND to LCD Pin 3


Board Installed in NerdKit LCD


Board Wired to NerdKit


Showing familiar welcome screen.

I have zipped up the files for the board, the Gerbers for manufacture (If you want), and the test program and libraries.  They can be downloaded here

This project was designed around a NerdKit.  The library files should be placed in the same folder as the default NerdKit libraries (libnerdkits).

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7 Responses to New board for I2C LCD Backpack

  1. wiredsel says:

    Hello, I’ve been seeing working on the project of Morse Decoder for
    ATtiny26L in, and i’ve attemping making one but, I have
    some troubles, could you please help me? i don’t have the library
    files of delay.c, uart.h and lcd.h (because i don’t have already the kit so i
    have the components) can you send me the librarys of nerdkits? Hope
    your answer, Thank you

    • Rick_S says:


      I am not affiliated with the Nerdkits people. I am just a kit owner and user. As such, their libraries (include files) are not mine to give out and are included as part of thier kit. I will admit I was quite skeptical at first when it came to purchasing thier kit because the hardware cost was marginal compared to their kit cost. However in hind sight, it was money well spent. They have an awesome forum (Which I am a part of) that rarely if ever turns ugly. A great group of helpful people with a support staff like no other.

      I will also say that most of thier libaries can be easily replaced with publicly available libraries with some program modifications. If you need UART / LCD functions, check my link to Peter Fleury Libraries. You’ll find UART and LCD libraries there. As for delays, the avrlibc libraries have delay functions, they are just used a bit differently.


  2. Ok got it to work once I sorted out my LCDs.

    Got at lest 3 LCDs that are not working, well one partially works, I’ll post some pictures.

    Thanks once again Rick!!


  3. Hey Rick the I2C_LCD_SOIC.brd file will not open in my version of Eagle!!

    “Invalid data in file” error!!


  4. Dragan says:

    I guess that you forgot to mention the manufacuter name/url?
    Nice design btw.

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