Go Down

Topic: Settings switches (Read 959 times) previous topic - next topic


I'm fairly new to this whole Arduino thing to be honest.
To be more honest, I have nearly no robotic experience at low-level.

(Which is why I chose Arduino; seemed friendly enough!)

Basically, in an attempt to use less I/O pins, I want to rely on an Uno board rather than a Mega. My problem is, I can think of only a very primitive way to use input pins.

My current problem is that I need a set of 8 switches (well, not need, but it seems best) for the software to decide what to do. The first 3 bits shall be used for which program to run (2^3 = 8 separate programs). The remaining 5 bits will be used for various other boolean settings.

Now the statement of the problem: I don't want to use 8 different pins. Especially, when considering digital terms, that's just a byte.

I'm a software guy. Low-level programming thrills a little part of me. I'm just not used to the hardware end of things.

If anyone has pointers to introductory I/O tutorials, hints, or hardware optimizations and methods, I would very much appreciate them!

Thanks for any replies that come in, and for your time in writing them!

PS: I'm fairly sure this is in the right subforum. It -could- go under software, but I have far more problems on th hardware side. I can deal with software mostly by myself.


Well there are several approaches to this, firstly I/O expanders - chips that take a few pins to drive (such as I2C) and provide 8 or 16 I/O pins (but lower bandwidth than direct pins).

Secondly you can use a resistor network to convert several switch inputs into an analog voltage to be read by one analog pin.  The absolute limit is 10 switches as the A/D converter is 10 bits, but in practice 5 or 6 per analog input would be plenty if you want to avoid problems of noise, linearity and component tolerances.  This approach is appealing in that a few resistors are all that's needed.

Also a simple shift-register or input-multiplexer approach would work - two approaches to rolling your own input expander.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Jan 20, 2011, 09:06 am Last Edit: Jan 20, 2011, 09:07 am by tkbyd Reason: 1
Another option, with a bit of an early learning curve, but the effort will repay you handsomely, is to use one of the Dallas Semiconductor 1-Wire chips. That would give you 8 inputs for the "price" of one Arduino I/O bit.

1-Wire is often used by Arduino forum folk for the temperature sensors in the product line, but there are many, many other devices which work the same way. The 8 bit I/O chip is the DS2408, dta sheet....


I believe it can be configured to "catch" transient inputs, too... so you don't need to monitor the lines intensively.

More on 1-Wire generally at...


Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131