Picaxe as an I/O expander for Arduino
February 12, 2013
As I was thinking of new features for my robot, I realised how painfully short I was on pins! The Arduino Mini just doesn't have enough! I'm not thinking of upgrading to a Mega, seeing how pricey it is and also because it's pretty huge. That's when I though of I/O expanders. Unfortunately, most are designed to be shields for anything but the Arduino Mini, so, again, I didn't know what to do. That's when I thought of using a Picaxe for expanding! I'm thinking of using a PWM or an analog pin from the Arduino as an output to a Picaxe input pin. Different ranges of PWM/Voltage the pin issues correspond to different pins on the Picaxe being turned HIGH or LOW. Let's say 1 to 10 PWM means Pin 1 and a 255 PWM signal following in the next milliseconds signals HIGH, while a 0 PWM signal means LOW. Just a basic idea of a communication protocol using 1 pin.
Also, why Picaxe? I think Picaxe boards are very cheap and small, which gives them an advantage over the bulky and more expensive I/O expanders I've looked at.
This is just a thought I wanted to share, and I also wanted to get some comments on the feasability of such a thing. If it works, I end up saving LOTS AND LOTS of pins on the Arduino.
Also, I can't recall seeing a method like this used for any robot I've seen. Is it because there's a more convenient way of expanding? Maybe is there something obvious I missed?