Arduino Interface Hardware:
This page provides a collection of useful interfacing techniques including:
Find out what causes switch bounce and why your
microcontroller will have a problem with it! The real
problem is the spring in the switch but a bigger problem
is the microcontroller itself...
You may be surprised when you first accept input from a
push button, that it does not just generate a clean
output but actually
generates a lot of on/off signals in a very short space
If you are not careful, a single button press can
result in your code counting up 10's of button presses.
This is obviously not
useful if you want to increment a variable by one!
You have to get the switch under control and the link
below shows you some easy ways to do it.
You don't need to buy a toggle switch as it is possible
make one using only a push button and a microcontroller.
toggle remains in which ever state you leave it i.e. it
Making a toggle switch from a push button just requires
the Arduino to remember the current state of the switch.
Using a proper toggle switch gives a very nice feel to your projects. Find out here the two different ways you connect them up.
This tutorial showing you exactly how to read the outputs of the potentiometers but makes it simpler by using a new library.
Or how to save I/O pins when driving LEDs!
Charlieplexing uses a clever trick:
The fact that a reverse biased LED
is a diode that stops current flow.
Combined with the ability of microcontrollers to change
input to an output on the fly the circuit current flow
can easily be
altered to light specific LEDs, but more importantly you
more LEDs than there are controlling pins!
One problem you will come up against is the fact that
system uses 5 volts and the chip you want to use must
only have 3V3
(including the control signals). Its ok if the signals
are all going to
the 3V3 chip as you can then use voltage dividers.
The problem comes if you need to change direction with
same signal. Fortunately, there is a very elegant
solution using two
resistors and a MOSFET!
It's not the first thing that comes to mind when using
a rotary encoder:
They just don't work right -
producing all kinds of spurious signals.
Even though they use Grey encoding (that ensures only on signal changes from one movement to the next) they are still an absolute pain. It's all due to switch bouncing inside the device as the metal contacts bounce on and off the substrate when you rotate the shaft.There are several solutions such as capacitor smoothing but if you don't want to slow things down too much a more elegant solution is to use a state machine. In the code below you can get your rotary encoder to reliably output single digit changes with absolutely no skipping.
The I2C protocol saves you a lot of wiring as it is a 2
wire interface. Not only that, it is also a multi-drop -
system with bi-directional communication (Remember that
The I2C protocol allows communication in both directions between the master controller and slave devices so you can have very complex systems e.g. gathering data from an ADC and sending data to a display; all on same two wires.
The SPI interface is a much simpler interface than I2C,
because it is simpler it can operate far faster e.g. a
typical I2C rate
is 400kHz but SPI is 10MHz. Updates to I2C let it go at
~3MHz but never
as fast as SPI.
Lots of chips implement SPI for this reason; Sometimes
have to get a faster data throughput at the expense of a
Have your say about what you just read! Leave me a comment in the box below.
Don’t see the comments box? Log in to your Facebook account, give Facebook consent, then return to this page and refresh it.