AnalogMux is an Arduino-based interface to a SparkFun 16-Channel Analog Multiplexer breakout board.
HackPittsburgh has launched two high-altitude balloon projects.
One was successful, one was not. Our third launch is pending, and the payload is anticipated to
include a number of sensors not previously flown. This will challenge the Arduino-based flight
computer, given its limited number of analog inputs.
To address this limitation, a SparkFun 16-Channel Analog Multiplexer breakout board was selected. This board will allow up to 16 analog inputs to feed into one Arduino analog input pin. This requires four digital outputs from the Arduino used to select which analog input is connected to the Arduino.
This software library provides an interface to the multiplexer.
Previous balloon launch photos are available at the HackPittsburgh Flickr Pool. My favorites, plus my ground photos, are in My Flickr set.
- An Arduino (http://arduino.cc)
- Arduino 0021 (http://arduino.cc)
- SparkFun Analog Mux Breakout (http://www.sparkfun.com/commerce/product_info.php?products_id=9056)
To use AnalogMux in your project, you must ensure that a few preprocessor definitions are accurate, and you must of course wire up the proper circuit. The best place to see what is required is in the code itself. If you have any questions, email me.
Initialize the analog multiplexer by calling the initAnalogMux function. This function requires
that the Arduino pins to which the multiplexer's S0, S1, S2, and S3 inputs be specified as
parameters.
Initially, channel 0 is selected. To select a different channel, call selectAnalogMuxChannel with
the number of the channel, 0 - 15, to select. The analog voltage can then be read from the analog
input pin using the built-in analogRead function.
AnalogMux is completely and utterly untested and unreviewed. The code compiles, and that's all. I tried to be careful with the coding and design, and I read the datasheet. Nevertheless, I haven't actually run this thing yet.
The chip on the SparkFun Analog Mux Breakout, the TI CD74HC4067, supports an enable line that will turn off all of the analog inputs. This is currently unsupported in the library.
It would also be nice to package this up better some day.
- Initial release (totally untested)
The MIT License
Copyright (c) 2010 Jonathan Speicher
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
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copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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