Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by MTset on Fri Mar 22, 2013 8:23 pm

Since this kit uses the I2C expander and I2C is stackable is it possible to run multiple units on the I2C bus?
What steps would have to be taken? I assume some addressing issues would have to be handled. Anybody try this already?
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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by tldr on Fri Mar 22, 2013 11:24 pm

you can use as many as eight of these plates. addresses can be set by cutting some traces and shorting some pads on the back of the board under the mcp23017 chip.

matter of fact, a second i2c bus is brought on the unpopulated header between the cpu and the ethernet controller on the pi, so you could use 16.
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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by MTset on Wed Apr 03, 2013 5:07 pm

Thanks for the reply! Are the steps for addressing difficult or outlined in the datasheet or online? I figured the addressing would be handled via software and drivers rather than hardware.
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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by adafruit_support_mike on Thu Apr 04, 2013 10:17 pm

I2C addresses are handled in hardware. The details are explained in the MCP23017's datasheet (http://www.adafruit.com/datasheets/mcp23017.pdf), but the short version is that the address pins are the three closest to the buttons along the outer edge of the PCB.

By default, those pins are connected to GND to give the device an address of 0x20. There are three sets of pads on the back of the PCB that will let you select any of the 8 possible addresses you want though: http://learn.adafruit.com/assets/2646
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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by voc on Tue Sep 17, 2013 6:27 am

Sorry to resurrect this posting but is there a small how-to somewhere with pictures how to accomplish this.

Addressing should be simple if you look at this picture:

Image
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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by adafruit_support_bill on Tue Sep 17, 2013 6:44 am

Don't have a how-to with photos. Although that would be a good addition to the basic tutorial. Looking at the photo below: the 3 sets of jumper pads below the soldering iron are (from right to left) A0 - A3. If you look closely, you will see 3 small bridges from the center pads to the upper pads. These are tying the address pins to GND. If you cut one of those bridges with a knife and solder a blob between the center pad and the lower pad, it will tie the address pin to 3.3v.


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Re: Multiple Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi?

by voc on Tue Sep 17, 2013 7:59 am

Thanks Bill!.

I'll heat up my Weller in a few hours when i'm back home :D
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