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welcome ladies and gentlemen fellow nerds
to my living room
uh... you're looking at a video about calculator link programming
and i've made this because I've had several questions from several different people
about calculator linking
and i thought I'd make a nice video to explain things a bit
I am Tim Franssen, also known as Timendus online
and i've made several
link applications, API's, protocols
what I'd like to start with is the OSI model. The OSI model is the model that
the internet uses
and as you can see it's structured in a very layered way
so that means that we start with
a physical layer
that's the cabling but it can also be
uh... wireless
network for example, that's also physical layer
And on top of that there's a data link layer which makes sure data comes
from one end of the connection to the other
On top of that is a network layer, so if we have
to route things
it makes sure that data gets from there to there
through here
Now, why am I showing you this? I'm showing you this because
it's important to understand that the differently layers do not have all that much
interaction
they were designed independently of each other
that means that the physical layer
uh... has absolutely no knowledge of the data link layer
and the data link layer has absolutely no knowledge of the network layer
And the other way around
it also goes, so the
network layer has absolutely no knowledge about the data link layer and the data link layer has no knowledge of the physical layer
all they do is
their own job, their own small little task and nothing else
now want you to keep that in mind, that idea
of having differently layers doing just one simple thing
when we go to calculator
networking
so i made this
uh... And I call it the calculator
networking
uh...
stack
we start with the physical layer, but this is all in software ofcourse
We're not really talking about the copper here
i'm talking about the bit of software that makes sure that on this copper we get zeros
and ones
bits
uh...
that can form messages
now that's the first layer, we have to make sure that we can do this
we can send zeros and ones across a line
if we can do that
we're halfway there
secondly at the byte layer we must make sure that we can combine these bits
into sensible bytes
This is a very nice byte
uh...
then there's a third layer, the data layer that combines bytes to make strings
blocks uh... allows you to send double registers all that kind of stuff
and then there's a fourth layer
the networking layer, I've...
done a few things in my CLAP project
uh... and the fifth layer is the application layer. What are you doing with this
calculator linking
in your application, how does it fit in.
uh... i'm going to try and make five videos, so this is the first, and I'll talk about
the physical layer in this first
and the other four i hope to address in some layer videos, no promisses though
Okay, so the first
part of this is the physical part
The physical layer, how to send a bit across a piece of copper, because that's all it is
let's be honest
um... this is nothing special
it's just wire, so if I put a current on here, say plus five volts
Oh I can't write with a mouse
and you connect this to the ground
that's important you always have to compare voltage
compared to something
uh... that on this and we also get five volts
and we also get a ground