Voltage Data Through Bluetooth

Hello Everyone,
Apologies if this has been asked before. I’m basically a newbie on BeagleBone Boards but have a basic background on programming.

Now part of my project is supposed to gather data from a power source, it will basically act as a voltmeter. My idea is to send this data either via a Bluetooth dongle or wireless to
a phone running android, in which it will be displayed as a graph real-time. Any ideas on where can I start?. I took a look at some other projects but these use an arduino to read
the voltages and then send it to the Beaglebone, I would prefer if everything is done on the BeagleBone as the whole actual project will be based on it.

If anyone have any idea, please let me know.

Thanks

Any ideas on where can I start?

Yes. You can start by learning about the on die ADC, and how to buffer the voltage input. That is, the BBB can not take much more than 1.8v on the ADC input, so you’d need to scale that down. I’m not an electronics engineer by any stretch of the imagination, so exactly how is best, I’m not sure.

Passed that, knowing C reasonably well, and learning the libc function / API calls is pretty much a must. For this, you’re either going to need to understand how to use sysfs, or mmap() to access the ADC. Once you get that down, you’ll need some way to get the data out over the wire. There are more than a couple ways to do this. But you could use a shared memory file to store the data from your C application above, and a Nodejs app to put the data out over the wire. You could even directly call a C application as mentioned above through Nodejs. Or you could use strictly C with something like libmongoose, to put the data out over a websocket - To any listening browser clients.

Not 100% sure here, But I think Jasons bonescript may be able to do most if not all of the above as well. No hands on here, so could not say for sure.

Personally, I prefer the all C approach, but thats me.

Also since you mention you’re new to this whole “thing”. I would highly recommend this book.

http://www.amazon.com/Exploring-BeagleBone-Techniques-Building-Embedded/dp/1118935128

*Any ideas on where can I start?*

Yes. You can start by learning about the on die ADC, and how to buffer the
voltage input. That is, the BBB can not take much more than 1.8v on the ADC
input, so you'd need to scale that down. I'm not an electronics engineer by
any stretch of the imagination, so exactly how is best, I'm not sure.

One of the more reasonable failsafe options is to use an op amp that
will run at 1.8 volts vcc, use it in a non-inverting configuration,
and use it to scale the voltage to your A/D input. You must have a
part that will do rail to rail (0 volts to vcc), or you must take
steps to use the available range. Also, do check the maximum readable
input on the chip, which may not be the maximum input voltage, and may
well be less. This would be your maximum voltage output from the amp.

The reason for an op-amp is that it is easier to get a high input
impedance for your measurement and also the op-amp itself can afford
some protection for the processor's ADC in an overload situation.

Harvey