I/O Expander Shield

Hello, I started a new project and I have to use many pins not only for input but for output too and all the pins my Arduino Uno has just aren't enough. I also don't want to use a shift register only, because I don't know how to handle things like a LCD display with them. Can I use one of the shield or the breakouts from Sparkfun? Or do you have any other/better ideas?

SparkFun PWM Shield or SparkFun I2C Expander Breakout - PCF8575

with Female Headers

Thanks in advance for quick answers.

How many without shift registers would be enough? The Atmega1284P provides 32 IO (vs 20 on '328P) vs many more on a '2560. Some examples of boards I offer that IDE supports with a minor addition: http://www.crossroadsfencing.com/BobuinoRev17/ |500x209 |500x296

Thanks for answer. I think I will maybe need up to 24 pins. As far as I know the Atmega1284P is another microcontroller. Should I use it with the Aurduino in combination or is there a way to give the Arduino itself more pins?

Well, it is pretty straightforward.

If you want lots of PWM, then the PWM shield is the way to go. If you want more inputs, you want the PCF8575. You can use both (or more) as they connect (together) to the I2C bus.

Why not just use a mega...?

It'll be cheaper to buy a mega than to expand your UNO with a port expander and easier to program...

Yes, 1284P is another microcontroller, you would use it as a replacement for a '328P board.

C-F-K: Why not just use a mega...? [...]

Because the uno is what I have at home :)

Paul__B: [...] If you want lots of PWM, then the PWM shield is the way to go. If you want more inputs, you want the PCF8575. You can use both (or more) as they connect (together) to the I2C bus.

So I would just have to decide between pin or pins with pwm, right?

CorCl: So I would just have to decide between pin or pins with pwm, right?

Well, you have to count them. Since the PWM expander uses only 2 pins, you would have all the other Arduino pins available as inputs.