In this video I’m going to review the Digilent
Analog Discovery and look how it can be used
for the analysis of analog and digital circuits.
The Analog Discovery combined with the Waveforms
software forms: a 2 channel USB oscilloscope;
a 2 channel waveform generator; a 16-channel
digital pattern generator shared with a 16-channel
logic analyser; and more, in a single package.
It is priced at $99 for US students and $219
for non-academics. That is very competitive
in comparison to separate tools and it is
a very neat package that is ideal for university
teaching and independent learning.
So, the package comes with the analog discovery
unit that connects to the PC using the supplied
micro-usb cable. As all of the cables on the
loom are female terminated there are also
some male headers. As an accessory, there
is a BNC adapter board available for $20 that
plugs into the Analog Discovery and allows
you to use BNC terminated test leads and probes.
There are better professional specification
tools available for each of the devices, but
as a reasonably low cost-solution for education
and independent learning, the tools are very
feature rich. I’ll demonstrate this in the
video by looking at three different applications:
First, I will use a standard rectifier diode
and look at how we can connect a basic circuit
that uses the Analog Discovery to characterise
its behaviour. I also look at the more advanced
analog features that are available.
Secondly, I look at how we can use the digital
pattern generator and logic analyser to investigate
the behaviour of a JK flip-flop, without using
any additional circuitry or power supplies.
Finally, I look at how we can use the Analog
Discovery logic analyser and its I2C interpreter
to connect to the Beaglebone I2C bus and analyse
how it behaves when we use the Linux i2c tools.
This is an introductory video so you can skip
to the section that interests you by jumping
to the timestamps that are displayed here.
So, just very briefly, the Waveforms software
requires a Windows PC and you can install
it by following the Download link at the top
right-hand corner of the Waveforms site. There
is a Linux SDK that exposes features of the
Waveforms API (it’s not Waveforms for Linux),
but I haven’t looked at that yet. It installs
fairly easily and detects the device. One
feature is that Waveforms will work without
the Analog Discovery using an audio input;
however, it can be confusing when you accidently
plug out the Discovery that superficially
everything looks like it is working, but the
inputs are not as you expect!
For the first part of this video I am going
to look at the Digilent waveform software
connected to the analog discovery I am going
to look at the analog side. So, I’m going
to use the scope and waveform generator. For
this circuit I’m going to use a 1N4004 which
is a basic rectifier diode. So, for this circuit
which is a standard circuit if you were getting
started with analog electronics, so lets see
how this type of setup performs with this
type of circuit and how you would connected
it up. So, here I have my diode with the anode
cathode in this direction, so current flows
when the diode is forward biased.
So, I am going to connect up my scope 1+ and
1- is my first input, 2+ and 2- are my second
inputs. I’m going to use W1 which is my
waveform output and any of the ground lines.
1+ to the input side of the diode. 1- To the
common point. 2+ blue wire is the output of
the circuit. 2- Blue wire with white stripe
connected to ground, any black wire. W1 is
the waveform input
The cables are female ended cables so I have
added male headers to the board.
So, that’s my circuit wired. We can then
startup the software
We can look at the scope and waveform generator
which is very powerful – very feature rich.
Here is the waveform generator that allows
us to generate waves of any type. We can set
the amplitude and frequency. Let’s leave
the frequency at 1KHz.
If we look at the output we can run this and
see what we get. I forgot to start the wave
generator. Start the wave generator and it
is as we would expect. Set the offsets so
we can overlay the two waves. Now you can
see when we zoom in by changing the timebase,
down to 200ms. So, that is the characteristic
we would expect of a pn-junction diode. You
can see the orange signal is the input and
the output is the blue. You can see we have
a voltage drop due to the pn-junction. When
the circuit is reverse biased we do not get
a current flowing, so this is the characteristic
we would expect from this type of diode. We
can measure. Add in measurements on channel
1 (input) we can get the maximum, add the
minimum, peak-to-peak, amplitude and on channel
2 we can get 
the maximum, amplitude, minimum.
We have our values. The maximum +3V, the minimum
on the negative 170mV. Single to pause. Amplitude
on the output is 1.4V on the input 
is 3V perfect.
So, in conclusion the Analog Discovery coupled
with Waveforms provides a rich set of tools.
Okay, they are limited on 
the analog side to a 5MHz bandwidth and 
on the digital side it is limited to 16 channels
and 100 Million samples per second. However,
as a teaching and independent learning tool
it is ideal. Also, for hobbyists it is a great
way to become familiar with 
the type of features that you would like to
have available 
in more expensive hardware. If you 
know 
of better solutions, please let me know.
