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Mini Mayhem

I received another toy to play with as a Christmas gift from my in-laws – a Netduino Mini. It has most of the power of it’s bigger brother, boiled down into a tinier package. It does have some limitations such as only one serial UART and a couple fewer I/O pins, but those are pretty minor.

I knew that I wanted to use the Mini in my next generation pump control box to replace the PICAXE 28×1, and that meant the serial UART had to be used for communications to and from the XBee wireless modem. This also meant that all my LCD backpacks were essentially worthless – I wouldn’t have any way to communicate to them without a second UART. After some digging around on the web, I found Adafruit’s I2C backpack and Szymon Kobalczyk’s uLiquidCrystal library and I was back in business.

After some prototyping success and more consideration, I realized that if the backpack was using a MCP23008 digital I/O expander, this same circuit layout and code should work for the larger MCP23016 and MCP23017 digital I/O expanders, but with the added bonus of the chip driving a LCD display, as well as 9 pins worth of LED outputs and switch inputs. I could actually use a single MCP23017 IC to handle all display information for the control box panel!

The screenshot to the left shows the MCP23017 LCD interface in action. It displays a 3 line message, followed by a fourth line with a count of the milliseconds since the program initiated and a custom smiley-faced character (part of Szymon’s test programs that I lifted and threw into my test). The last 3 digits of the milliseconds don’t show up well in the photo because they change so fast, but you get the idea.

There is plenty of testing and prototyping that remains before I can gut and reassemble the pump control box, however these little steps form the building blocks of the transformation. I also have several large 20 gallon batches on the near horizon that will require my box and grant to be operational, so I don’t want to do anything rash before I can part with it for a few weeks.

I’ve been working on some other circuitry mayhem utilizing PICAXE 08M modules and high-intensity RGB LEDs – that particular project has more work to be done before I unveil it, however. It definitely embodies the whole “needless but cool use of technology” that makes me grin, and I’d be suprised if a few folks didn’t want some for their own… Mwaaa haa haa.

Categories: Tech geeks
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  1. December 29, 2013 at 3:05 pm

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