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Adafruit LCD MCP23017 IC

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#1 knehowig


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Posted 05 January 2013 - 04:53 PM

I'm having a weird problem with the Adafruit LCD shield, specifically with the MCP23017 chip sitting on the I2C bus.


My setup:


Netduino Plus

4.2 firmware

My app is in VB

Using the Toolbox driver for this shield


Everything builds fine and starts up well. I get an initial sign on message to display on the LCD and can read the buttons fine. My app periodically writes new data to the LCD (about every 3 seconds or so). At random, the LCD/buttons stop working. My app continues to run fine, but when I attempt to write to the LCD or read the state of the buttons, nothing on the shield works.


I can set breakpoints in my code and everything looks fine -- it executes the Display.Write command to the LCD, but just returns without putting anything on the LCD once it is "locked up".


I suspect a problem with the I2C interface (the only way to recover from this is to power down the board).


Any thoughts?



#2 JimmyNet



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Posted 13 January 2013 - 02:32 PM

I have the same isseu, don't know what it is.

#3 AxelG


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Posted 29 January 2013 - 01:44 AM

Can you post a schematic?


I2C is sensitive to the pullup resistor values used on the SDA SCL wires.

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