Getting Arduino and Arduino-like boards working properly under Linux can be a troublesome task if you are not familiar with how Linux works.
So I am going to introduce you to some of the basic tools you will need to work out why your board isn't working as you'd like it to work.
I thought the other day I would grab a couple of these cheap little LED volt & amp meters modules you see on eBay. 30V, 10A, red and blue LED displays. Funky little things. I felt I should take a look at them and see just what they are, what they do, how you use them, etc.
Now of course, true to form, the details on eBay are very sketchy about how to use them. This is all it has to say on the page I bought mine from about the wiring:
The Arduino (and many other boards) have a very useful time-and-cost saving feature ideal for when you are working with buttons and switches - namely internal pull-up resistors on the GPIO pins which can be enabled / disabled at will in software. This means you don't have to clutter your board up with pull-up resistors of your own for all the buttons and things, and also means they can be turned off and on to give your design much more flexibility.
But nowhere can you find out actually what the resistance of these resistors are. Why not? Simply because nobody knows.
I don't know about you, but I have a huge pile of different Arduino-like boards here. (I have so many because I need to test UECIDE with them - or that's what I tell the "bank manager"). Many is the time I will have more than one of them plugged in to my computer. Often times I have programmed one of them with some code only to find it's not worked - and why hasn't it worked? Because I have had the wrong serial port selected in the IDE.
Logging data on an Arduino is very much a trivial every-day task. Connect an SD card, open a file, and start printing data to it.
For many people that is good enough. It results in nice easily readable (by us humans) data.
But it's not fast. It's not efficient. It's perfectly fine for things like logging temperature every hour, or barometric pressure every 5 minutes, etc. But when you have large amounts of data to store very rapidly you have to think a little differently.
So many people starting out in electronics, especially beginning to dabble in the world of Arduino and similar boards, just don't have the basic equipment to do the job properly. And not only that, they don't even know what the basic equipment is.
So here's a list of things you should have on your desk no matter if you have just got your first Arduino or if, like me, you are a seasoned veteran.
My latest acquisition, the Dragino Yun Shield is actually quite a nice bit of kit. It's the Linux portion of an Arduino Yun placed on a shield, so you can attach it to any board of your choosing.
It provides both a UART and an SPI connection to whatever it is plugged in to. And that includes chipKIT boards.
So there's the Arduino Yun. That's quite a nice concept - an embedded Linux computer (MIPS based, YAY!) and microcontroller combined on one board. Just such a shame it's an Atmel microcontroller and not a PIC32.
Everyone, when they're starting out on the Arduino and similar boards, learns to use the String object for working with text. Or they think they do.
Well, you should forget all you think you have learned about using Strings on the Arduino, because it is all wrong.
There are many sensors out there which output a voltage as a function of the supply voltage as their sensed value. Temperature sensors, light sensors, all sorts.
Measuring that voltage, and converting it in to real figures for whatever is being sensed is not actually as simple as you might at first think.
There are many examples on the internet for converting an ADC value into a voltage, but basically it boils down to:
