16x2 LCD display i2c - More than one?
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16x2 LCD display i2c - More than one?

by pprovost on Tue Jan 01, 2013 12:24 pm

Hi all,

I just got some 16x2 display w/ shield kits. They are working nicely. I would like to daisy chain them and drive them from a single Pi. The MCP23017 controller has three address lines, so I guess I could chain up to 8 displays on the i2c bus. Is that right? Any way I can hack the PCB to set different addresses? Sure, I could put it on an external board, solder some leads to the PCB and do as I please, but I quite like the format of the display attached to the PCB.

Any advice or suggestions? Can I drive 8 16x2 displays through i2c from a single Raspberry Pi?

Thanks!

Paul
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Re: 16x2 LCD display i2c - More than one?

by adafruit_support_bill on Wed Jan 02, 2013 6:53 am

With a little address hacking, you should be able to drive 8 boards on the same I2C bus.
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Re: 16x2 LCD display i2c - More than one?

by pprovost on Wed Jan 02, 2013 8:17 am

Thanks for the answer.

So can I hack the Pi Plate to do this, or do I have to bring the MCP23017 to an outside board and do the address hacking there? I see three tabs in the back of the board. Are these the address lines?

Please advise!

Paul

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Re: 16x2 LCD display i2c - More than one?

by adafruit_support_bill on Wed Jan 02, 2013 8:24 am

I don't have one on hand to verify, but it looks like those pads are adjacent to the address pins on the chip. I'll check further to confirm.
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Re: 16x2 LCD display i2c - More than one?

by adafruit on Wed Jan 02, 2013 10:22 am

Those are address pins and you can cut the trace on the middle pads on one side to ground and then solder the middle pads to t he other side to adjust the address. however, its not supported and we dont have any tutorials on it, just something we tossed onto the PCBs for fun :)
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Re: 16x2 LCD display i2c - More than one?

by pprovost on Wed Jan 02, 2013 12:04 pm

Just as I thought. Thanks! Will have fun!

Can you draw me up where I have to cut the trace and where to solder?

Paul
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Re: 16x2 LCD display i2c - More than one?

by adafruit_support_bill on Wed Jan 02, 2013 2:12 pm

If you look closely: for each set of three pads, the middle pad will be connected to one of the others. Cut the connecting trace, and use a drop of solder to bridge to the pad on the other side.
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Re: 16x2 LCD display i2c - More than one?

by pprovost on Wed Jan 02, 2013 4:02 pm

Got it. I guess the eyes aren't what they used to be <puts glasses on>.

Thanks for your help, sonny!
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