Xbee modules provide a very simple way to add a wireless capability to communications on Arduino. Essentially they let you work in exactly the same way as a direct serial connection between two boards – albeit wirelessly.
The easiest way to connect an Xbee to your Arduino, is to use the Arduino Wireless Shield.
It’s possible to connect Xbee’s without a shield – but given the fact that they don’t have the (standard) breadboard 0.
In my previous posts in this series I looked at a couple of ways to use an Arduino to generate analogue waveforms.
In this third part I look at a much simpler, IC-based digital to analog (DAC) circuit to provide the waveforms, and look at ways of changing the frequency of the output.
Let’s start with the new circuit.
In part two of this series, I used an R-2R ladder resistor network built from discrete components.
Last time, we looked at some Arduino code that we could use to generate some square waves.
The problem with the setup we’ve been looking at so far, is that we can only produce signals of one amplitude – equivalent to the HIGH logic level.
In order to be able to produce any other waveforms we’ll need to be able to produce a variety of different output voltages. Although the PWM method we looked at last time gives us a way to do this, it’s not suitable for producing variable waveforms – as it’s time-based.
I was looking around for an interesting Arduino project, and I came up with the idea of making a function generator (also called a signal generator). The reason I picked a function generator is that it gives us the chance of playing with some interesting circuits – and some interesting code…
Before we start with that – what is a function generator?
A function generator is a circuit that generates some kind of waveform.
Whilst you have quite a few outputs to play with on an Arduino board; sometimes there won’t be enough. One way to get around this is with the use of a shift register. This is a brilliant way to output eight pin’s worth of outputs – using just three pins. What’s more – it’s a fascinating insight into some elementary computer science…
I’m using the 74HC595 – purchased from the good folks at Oomlout.