The explosive growth of the “Internet of Things” is changing our world and the rapid drop in price for typical IoT components is allowing people to innovate new designs and products at home. In this first class in the specialization you will learn the importance of IoT in society, the current components of typical IoT devices and trends for the future. IoT design considerations, constraints and interfacing between the physical world and your device will also be covered. You will also learn how to make design trade-offs between hardware and software. We'll also cover key components of networking to ensure that students understand how to connect their device to the Internet. Please note that this course does not include discussion forums. Upon completing this course, you will be able to: 1. Define the term “Internet of Things” 2. State the technological trends which have led to IoT 3. Describe the impact of IoT on society 4. Define what an embedded system is in terms of its interface 5. Enumerate and describe the components of an embedded system 6. Describe the interactions of embedded systems with the physical world 7. Name the core hardware components most commonly used in IoT devices 8. Describe the interaction between software and hardware in an IoT device 9. Describe the role of an operating system to support software in an IoT device 10. Explain the use of networking and basic networking hardware 11. Describe the structure of the Internet 12. Describe the meaning of a “network protocol” 13. Explain MANETs and their relation to IoT
Lecture 1.3: Microcontroller Properties
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Del curso dictado por University of California, Irvine
Introduction to the Internet of Things and Embedded Systems
3849 calificaciones
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University of California, Irvine
3849 calificaciones
Curso 1 de 6 en SpecializationAn Introduction to Programming the Internet of Things (IOT)
De la lección
Hardware and Software
IoT devices are implemented using both hardware and software components. Dedicated hardware components are used to implement the interface with the physical world, and to perform tasks which are more computationally complex. Microcontrollers are used to execute software that interprets inputs and controls the system. This module discusses the roles of both the hardware and software components in the system. The functions of common hardware components are described and the interface between the software and hardware through the microcontroller is explained. IoT devices often use an operating system to support the interaction between the software and the microcontroller. We will define the role of an operating system in an IoT device and how an IoT operating system differs from a standard one.
Conoce a los instructores
Ian HarrisProfessor
Department of Computer Science
[MUSIC]
This lecture we'll talk about microcontroller specifically.
So when you're designing your project,
you're gonna have to decide on what type of microcontroller you're gonna use.
So this is a very early decision.
Actually probably it's the first decision you're gonna make is
which microcontroller will I use to control this system.
Because you can't write any software, or it's very difficult to write software
until you know at least what type of microcontroller you're gonna use.
So you've gotta make that decision.
So you can look in your data sheets and
try to understand which microcontrollers have the properties that you need.
Now these data sheets for microcontrollers are very big,
and they have tons of information.
And you don't need all of that at first, but there is some data out of that data
sheet rather that you need to understand in order to just pick apart, in order to
say look this is the microcontroller that will work for my system.
You need to understand certain information out of there so we'll go through that.
Right now the type of data that you need out of a data sheet
to make the first decisions about what microcontroller you will use.
And I should note that in this course,
in this specialization in general we'll focusing on Arduino and Raspberry pie so
they already have their microcontrollers built in so
we won't be making those decisions about which microcontroller fits for
this purpose or that because we're given those.
We're just using Arduino and the microcontroller in that.
Or Raspberry pie and the microcontroller and that.
But understand that outside of this class, in general when you make an IOT device,
you need to make this decision early on, which microcontroller you will use.
All right, so characteristics of a microcontroller that you need to consider
early on in order to pick which controller will work for your system.
So one is the data path bit width.
What that means is, it's the number of bits in each register.
Let me be more specific.
So there is data in this microcontroller,
there's lots of information floating around.
This information is represented as binary numbers, a series of zeros and ones.
A bit is a single binary number.
A single zero one that's a single digit.
A single binary digit is a bit.
Now, these numbers can be very large, right?
So, every data path, every microcontroller,
it has a certain, what you call a bit width.
The size of a standard piece of data in that microcontroller.
So common numbers would be like a 32-bit datapath for Microcontroller.
That means that most of the data inside that microcontroller is
gonna be represented as a 32 bit number.
A 32 bit sequence of zeroes and ones.
And that says a lot about the microcontroller.
It tells you something about the accuracy,
about how much data you can process at a time.
Because you are processing data in 32-bit chunks.
It tells you how big the registers are.
So we haven't said what a register is, but a registers basically just a storage
element, it stores data, it stores one number, essentially.
And so I, you have 32-bit registers, right?
To store 32-bit numbers, it also means, the buses that carry the data,
are generally 32-bits, 32 wires, running along the circuit, right?
So the bit width tells you a lot about the data path, and
generally high bit width means roughly more powerful.
It means you're handling more data at a time.
So if you take a 32-bit datapath compared to an 8-bit datapath,
you can handle 32-bit numbers instead of 8-bit numbers, so
you have more accuracy with the 32-bit number.
Also you can do generally more number crunching.
You can do more complicated things because you have 32-bits of data rather than 8.
So and actually between 8-bit and 32 bit is a common cut off so
if you look in Arduino, and Arduino is an 8-bit datapath, which is small.
And Raspberry Pie is a 32-bit datapath and there's a big cut off between those two.
For instance, just very roughly if using an operating system and
we will get to operating systems.
Operating systems, you can use an operating system on a 32-bit datapath,
but it's a very hard thing to have an operating system on an 8-bit datapath.
Right? So if you're thinking about your system,
well I need an operating system,
then you probably are not going to go with an 8-bit microcontroller.
You're probably gonna need a 32-bit microcontroller so
at a very high level the bitwidth is something you need to know and
that's gonna be on the front page of the data sheet, somewhere around there.
Input/Output Pins.
These are actually very important.
They're often a bottleneck.
So these chips, you've probably heard of Moore's Law.
Basically it says that chips get denser and denser every year.
They have more and more transistors on them every year,
so theoretically more powerful.
More power hungry too, but more powerful.
Now, even though the density is increasing at that rate, the number of pins,
meaning the number of connections to the outside world,
the wires that go to the outside that increases at a much more slow rate.
Okay?
So, you get more density on chip, but
the number of pins is barely increasing over time, slowly increasing over time.
So pins can be precious.
So, cuz remember the microcontroller is the center of the system.
It's connected to all the other components,
telling them receiving data from different sensors sending data to actuators,
talking to other integrated circuits on the device.
So the microcontroller,
it needs to be connected to other components in the design.
And so the number of input/output pins is really important and
you need to decide on that.
I find that's a big decision maker as far as what microcontroller I use because if I
know I need my microcontroller to connect to the following five devices and
these devices have x number of pins, I add that up and
I say wait I need a microcontroller that has at least five x pins, right?
So that rules out a lot of parts right off the bat.
So, the number of input/output pins tells you how well it can connect,
how many devices it can connect to in your system.
And so, that's actually an important factor.
If you look at Arduinos, well we'll get to that later, but Arduinos and
Raspberry Pi's don't have all that many pins.
And that many input/output pins.
That's okay for this class, but in general you might need more.
And so, Arduino for instance you could buy the Arduino uno,
which has a certain number of pins or you can go to the Do-A and
they have a series of Ardwinos and some of them have more pins than others.
So you can sort of upgrade the part you want if you know that your system needs
more connectivity to the microcontroller.
So input/output pins you'll also see that the front page, and
near the front page on the datasheet.
Performance of course, is important, how fast it operates.
Now we're gonna gloss over some of this because
judging how fast a microcontroller is involves a lot of things.
But the first thing is gonna be the clock rate, how fast the clock is.
So you'll be able to see a clock rate and
that should be again on the front page of the datasheet.
A clock just to briefly say, roughly one instruction is executed,
one machine code, one very simple instruction,
is executed every clock on your standard microcontroller.
And, standard single core microcontroller which is what we're dealing with.
So, if you want more instructions executed fast, you need a better clock rate so if
you have a clock rate of eight megahertz, right then that eight megahertz,
mega is million, that means you can have 8 million instructions in a second, up to.
Right?
Or, on the other hand, if you have one gigahertz,
then that means you can have a billion instructions in a second.
So, that's also a big cutoff commonly between 8-bit and 32-bit processors.
The 8-bits processor are all in this sort of 4 megahertz, 8 megahertz,
16 megahertz range, usually, where the 32-bit processes are up there in
the 500 megahertz/gigahertz range and higher.
So you get a big difference in speed there.
So you'll have to be able to make some sort of a rough estimate of
how much performance you need, and this is completely going to depend on
the application what the task is that's being performed.
Other features of a microprocessor that you might be interested in
examining in the data sheet before you pick which processor you are using.
Oh, and by the way, I said microprocessor here,
I'm using that interchangeably with the word microcontroller.
This is just a sliding scale between the two.
A microprocessor is a more complicated version of a microcontroller.
So I switch terms, but I mean the same thing.
Timers.
There are lots of different components inside microprocessors,
a timer's very common.
In fact not just very common, I think
a timer is in every microcontroller I've ever seen, you've some sort of timer.
You need timers for various things.
One thing is, when you're making these IOT devices,
they're often interacting with humans, right?
And, so they're often time delays involved with humans, for
instance, button pressing, actually, we'll get into more of this detail later.
But there are a lot of things where you want them to happen
on a certain time deadline.
Take sampling sound, right?
Maybe you want to sample sign of 4 kilohertz so you need to
trigger a sample to be recorded every 4000 times a second at a fixed rate.
Or say you got a video, right?
With video, maybe you want 30 frames a second,
then you need to trigger a frame to be produced 30 times every second.
So you need a timer for that.
So time is a very common.
Analog-to-Digital Converters, we talked about this.
How we need to do analog-to-digital conversion because
the world is through our perception is analog, we need to convert to digital.
So A-to-D converter is typically built in to these microprocessors and
microcontrollers.
Another important feature is low power modes so
power is important in processors these days.
Especially IOT devices, which are often portable, they run off of batteries, and
so people are very power-aware these days when they're doing their IOT design.
So it's common to look for
microcontrollers that have low-power modes which would shut off
parts of the microcontroller that you don't need to conserve power.
So power-saving is important and so for that reason you might look for
sort of sleep mode and you can have, this can get very complicated,
you can have basic sleep mode, deep sleep modes, all this.
So that's another feature that you can usually
see at least a notification that they exist at the beginning of the datasheet.
Now if you wanna understand more fully how they work,
you'd have to look deeper into the datasheet.
They'll have sections on the different low-power modes, and
how much power they consume.
Communication protocol support, so
here's another thing that you're often interested in the microcontroller.
The microcontroller has to communicate with lots of different devices.
So there will be, the center of the system, it has to communicate
with other integrated circuits and different components.
And the complicated components, like integrated circuits,
they send lots of data back and forth to the microcontroller and
the communication is complicated enough that it requires a communication protocol.
You can't just send a zero and a one, one at a time.
It's more complicated than that,
and they speak a certain protocol which is a sequence in which they send their bits.
So these protocols, there are a variety of protocols that are commonly used,
UART, I2C, SPI.
And we'll talk about a little bit these later, a little bit about them,
we'll touch on them.
But these are common protocols.
And the thing is, when you get other parts in the system like say your system's gonna
have the particular integrated circuit to do, video and coding or something, right?
That video and coding component, it might support only a subset of those protocols.
So, maybe this thing speaks I2C, but not SPI, right?
Or, maybe the other video and coding chip, it speaks SPI but not I2C.
So you need to be aware that, so when you get your microcontrol, you say look,
my video chip, it needs I2C, so I better get a microcontroller that supports I2C.
Or whatever protocol you're using.
So, this is another feature of a microcontroller that you can find in
the data sheet and you need to be able at least if you don't fully understand it,
at least be able to know, oh I2C, that's a protocol that matches the integrated
circuit service that I'm gonna buy and put in the rest of my system.
Thank you. [MUSIC]
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