<s>
A	O
single-board	B-Device
microcontroller	I-Device
is	O
a	O
microcontroller	B-Architecture
built	O
onto	O
a	O
single	O
printed	O
circuit	O
board	O
.	O
</s>
<s>
This	O
board	O
provides	O
all	O
of	O
the	O
circuitry	O
necessary	O
for	O
a	O
useful	O
control	O
task	O
:	O
a	O
microprocessor	B-Architecture
,	O
I/O	B-General_Concept
circuits	I-General_Concept
,	O
a	O
clock	O
generator	O
,	O
RAM	B-Architecture
,	O
stored	O
program	B-Device
memory	I-Device
and	O
any	O
necessary	O
support	O
ICs	O
.	O
</s>
<s>
As	O
they	O
are	O
usually	O
low-cost	O
,	O
and	O
have	O
an	O
especially	O
low	O
capital	O
cost	O
for	O
development	O
,	O
single-board	B-Device
microcontrollers	I-Device
have	O
long	O
been	O
popular	O
in	O
education	O
.	O
</s>
<s>
Single-board	B-Device
microcontrollers	I-Device
appeared	O
in	O
the	O
late	O
1970s	O
,	O
when	O
the	O
appearance	O
of	O
early	O
microprocessors	B-Architecture
,	O
such	O
as	O
the	O
6502	B-General_Concept
and	O
the	O
Z80	B-General_Concept
,	O
made	O
it	O
practical	O
to	O
build	O
an	O
entire	O
controller	O
on	O
a	O
single	O
board	O
,	O
as	O
well	O
as	O
affordable	O
to	O
dedicate	O
a	O
computer	O
to	O
a	O
relatively	O
minor	O
task	O
.	O
</s>
<s>
In	O
March	O
1976	O
,	O
Intel	O
announced	O
a	O
single-board	B-Device
computer	I-Device
product	O
that	O
integrated	O
all	O
of	O
the	O
support	O
components	O
required	O
for	O
their	O
8080	B-General_Concept
microprocessor	I-General_Concept
,	O
along	O
with	O
1	O
kilobyte	O
of	O
RAM	B-Architecture
,	O
4	O
kilobytes	O
of	O
user-programmable	O
ROM	O
,	O
and	O
48	O
lines	O
of	O
parallel	O
digital	O
I/O	B-General_Concept
with	O
line	O
drivers	O
.	O
</s>
<s>
The	O
board	O
also	O
offered	O
expansion	O
through	O
a	O
bus	B-General_Concept
connector	O
,	O
but	O
could	O
be	O
used	O
without	O
an	O
expansion	O
card	O
cage	O
when	O
applications	O
did	O
not	O
require	O
additional	O
hardware	O
.	O
</s>
<s>
Software	O
development	O
for	O
this	O
system	O
was	O
hosted	O
on	O
Intel	O
's	O
Intellec	O
MDS	O
microcomputer	O
development	O
system	O
;	O
this	O
provided	O
assembler	B-Language
and	O
PL/M	B-Language
support	O
,	O
and	O
permitted	O
in-circuit	B-Application
emulation	I-Application
for	O
debugging	O
.	O
</s>
<s>
RAM	B-Architecture
and	O
EPROM	B-General_Concept
were	O
separate	O
,	O
often	O
requiring	O
memory	O
management	O
or	O
refresh	O
circuitry	O
for	O
dynamic	O
memory	O
.	O
</s>
<s>
I/O	B-General_Concept
processing	O
might	O
have	O
been	O
carried	O
out	O
by	O
a	O
single	O
chip	O
such	O
as	O
the	O
8255	B-Device
,	O
but	O
frequently	O
required	O
several	O
more	O
chips	O
.	O
</s>
<s>
A	O
single-board	B-Device
microcontroller	I-Device
differs	O
from	O
a	O
single-board	B-Device
computer	I-Device
in	O
that	O
it	O
lacks	O
the	O
general-purpose	O
user	O
interface	O
and	O
mass	O
storage	O
interfaces	O
that	O
a	O
more	O
general-purpose	O
computer	O
would	O
have	O
.	O
</s>
<s>
Compared	O
to	O
a	O
microprocessor	B-Architecture
development	O
board	O
,	O
a	O
microcontroller	B-Device
board	I-Device
would	O
emphasize	O
digital	O
and	O
analog	O
control	O
interconnections	O
to	O
some	O
controlled	O
system	O
,	O
whereas	O
a	O
development	O
board	O
might	O
by	O
have	O
only	O
a	O
few	O
or	O
no	O
discrete	O
or	O
analog	O
input/output	B-General_Concept
devices	I-General_Concept
.	O
</s>
<s>
The	O
bus	B-General_Concept
of	O
the	O
early	O
single-board	O
devices	O
,	O
such	O
as	O
the	O
Z80	B-General_Concept
and	O
6502	B-General_Concept
,	O
was	O
universally	O
a	O
Von	B-Architecture
Neumann	I-Architecture
architecture	I-Architecture
.	O
</s>
<s>
Program	O
and	O
data	O
memory	O
were	O
accessed	O
via	O
the	O
same	O
shared	O
bus	B-General_Concept
,	O
even	O
though	O
they	O
were	O
stored	O
in	O
fundamentally	O
different	O
types	O
of	O
memory	O
:	O
ROM	B-Device
for	O
programs	O
and	O
RAM	B-Architecture
for	O
data	O
.	O
</s>
<s>
This	O
bus	B-General_Concept
architecture	O
was	O
needed	O
to	O
economise	O
the	O
number	O
of	O
pins	O
needed	O
from	O
the	O
limited	O
40	O
available	O
for	O
the	O
processor	O
's	O
ubiquitous	O
dual-in-line	O
IC	O
package	O
.	O
</s>
<s>
It	O
was	O
common	O
to	O
offer	O
access	O
to	O
the	O
internal	B-General_Concept
bus	I-General_Concept
through	O
an	O
expansion	O
connector	O
,	O
or	O
at	O
least	O
provide	O
space	O
for	O
a	O
connector	O
to	O
be	O
soldered	O
on	O
.	O
</s>
<s>
Typical	O
expansions	O
would	O
be	O
I/O	B-General_Concept
devices	I-General_Concept
or	O
additional	O
memory	O
.	O
</s>
<s>
Later	O
,	O
when	O
single-chip	O
microcontrollers	B-Architecture
,	O
such	O
as	O
the	O
8048	B-Device
,	O
became	O
available	O
,	O
the	O
bus	B-General_Concept
no	O
longer	O
needed	O
to	O
be	O
exposed	O
outside	O
the	O
package	O
,	O
as	O
all	O
necessary	O
memory	O
could	O
be	O
provided	O
within	O
the	O
chip	O
package	O
.	O
</s>
<s>
This	O
generation	O
of	O
processors	O
used	O
a	O
Harvard	B-Architecture
architecture	I-Architecture
with	O
separate	O
program	O
and	O
data	B-General_Concept
buses	I-General_Concept
,	O
both	O
internal	O
to	O
the	O
chip	O
.	O
</s>
<s>
Many	O
of	O
these	O
processors	O
used	O
a	O
modified	B-Device
Harvard	I-Device
architecture	I-Device
,	O
where	O
some	O
write	O
access	O
was	O
possible	O
to	O
the	O
program	O
data	O
space	O
,	O
thus	O
permitting	O
in-circuit	B-Device
programming	I-Device
.	O
</s>
<s>
None	O
of	O
these	O
processors	O
required	O
,	O
or	O
supported	O
,	O
a	O
Harvard	O
bus	B-General_Concept
across	O
a	O
single-board	B-Device
microcontroller	I-Device
.	O
</s>
<s>
When	O
they	O
supported	O
a	O
bus	B-General_Concept
for	O
expansion	O
of	O
peripherals	O
,	O
a	O
dedicated	O
I/O	B-General_Concept
bus	I-General_Concept
,	O
such	O
as	O
I²C	O
,	O
1-Wire	O
or	O
various	O
serial	O
buses	O
,	O
was	O
used	O
.	O
</s>
<s>
Some	O
microcontroller	B-Device
boards	I-Device
using	O
a	O
general-purpose	O
microprocessor	B-Architecture
can	O
bring	O
the	O
address	O
and	O
data	B-General_Concept
bus	I-General_Concept
of	O
the	O
processor	O
to	O
an	O
expansion	O
connector	O
,	O
allowing	O
additional	O
memory	O
or	O
peripherals	O
to	O
be	O
added	O
.	O
</s>
<s>
Microcontroller	B-Architecture
systems	O
provide	O
multiple	O
forms	O
of	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
signals	O
to	O
allow	O
application	O
software	O
to	O
control	O
an	O
external	O
"	O
real-world	O
"	O
system	O
.	O
</s>
<s>
Discrete	O
digital	O
I/O	B-General_Concept
provides	O
a	O
single	O
bit	O
of	O
data	O
(	O
on	O
or	O
off	O
)	O
.	O
</s>
<s>
Analog	O
signals	O
,	O
representing	O
a	O
continuous	O
variable	O
range	O
,	O
such	O
as	O
temperature	O
or	O
pressure	O
,	O
can	O
also	O
be	O
inputs	O
and	O
outputs	O
for	O
microcontrollers	B-Architecture
.	O
</s>
<s>
Discrete	O
digital	O
inputs	O
and	O
outputs	O
might	O
be	O
buffered	O
from	O
the	O
microprocessor	B-Architecture
data	B-General_Concept
bus	I-General_Concept
only	O
by	O
an	O
addressable	O
latch	O
,	O
or	O
might	O
be	O
operated	O
by	O
a	O
specialized	O
input/output	B-General_Concept
IC	O
,	O
such	O
as	O
an	O
Intel	B-Device
8255	I-Device
or	O
Motorola	O
6821	O
parallel	B-General_Concept
input/output	I-General_Concept
adapter	I-General_Concept
.	O
</s>
<s>
Later	O
single-chip	O
microcontrollers	B-Architecture
have	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
pins	O
available	O
.	O
</s>
<s>
These	O
input/output	B-General_Concept
circuits	O
usually	O
do	O
not	O
provide	O
enough	O
current	O
to	O
directly	O
operate	O
devices	O
like	O
lamps	O
or	O
motors	O
,	O
so	O
solid-state	O
relays	O
are	O
operated	O
by	O
the	O
microcontroller	B-Architecture
digital	O
outputs	O
,	O
and	O
inputs	O
are	O
isolated	O
by	O
signal	O
conditioning	O
level-shifting	O
and	O
protection	O
circuits	O
.	O
</s>
<s>
One	O
or	O
more	O
analog	O
inputs	O
,	O
with	O
an	O
analog	O
multiplexer	O
and	O
common	O
analog-to-digital	O
converter	O
,	O
are	O
found	O
on	O
some	O
microcontroller	B-Device
boards	I-Device
.	O
</s>
<s>
Analog	O
outputs	O
may	O
use	O
a	O
digital-to-analog	O
converter	O
or	O
,	O
on	O
some	O
microcontrollers	B-Architecture
,	O
may	O
be	O
controlled	O
by	O
pulse-width	B-Algorithm
modulation	I-Algorithm
.	O
</s>
<s>
It	O
is	O
common	O
practice	O
for	O
boards	O
to	O
include	O
"	O
prototyping	O
areas	O
"	O
,	O
areas	O
of	O
the	O
board	O
laid	O
out	O
as	O
a	O
solderable	O
breadboard	O
area	O
with	O
the	O
bus	B-General_Concept
and	O
power	O
rails	O
available	O
,	O
but	O
without	O
a	O
defined	O
circuit	O
.	O
</s>
<s>
Several	O
controllers	O
,	O
particularly	O
those	O
intended	O
for	O
training	O
,	O
also	O
include	O
a	O
pluggable	O
,	O
re-usable	O
breadboard	O
for	O
easy	O
prototyping	O
of	O
extra	O
I/O	B-General_Concept
circuits	I-General_Concept
that	O
could	O
be	O
changed	O
or	O
removed	O
for	O
later	O
projects	O
.	O
</s>
<s>
Communications	O
interfaces	O
vary	O
depending	O
on	O
the	O
age	O
of	O
the	O
microcontroller	B-Architecture
system	O
.	O
</s>
<s>
Early	O
systems	O
might	O
implement	O
a	O
serial	B-Protocol
port	I-Protocol
to	O
provide	O
RS-232	O
or	O
current	O
loop	O
.	O
</s>
<s>
The	O
serial	B-Protocol
port	I-Protocol
could	O
be	O
used	O
by	O
the	O
application	O
program	O
or	O
could	O
be	O
used	O
,	O
in	O
conjunction	O
with	O
a	O
monitor	O
ROM	B-Device
,	O
to	O
transfer	O
programs	O
into	O
the	O
microcontroller	B-Architecture
memory	O
.	O
</s>
<s>
Current	O
microcontrollers	B-Architecture
may	O
support	O
USB	B-Protocol
,	O
wireless	O
networks	O
(	O
Wi-Fi	O
,	O
Zigbee	B-Protocol
,	O
or	O
others	O
)	O
,	O
or	O
provide	O
an	O
Ethernet	O
connection	O
.	O
</s>
<s>
In	O
addition	O
,	O
they	O
may	O
support	O
a	O
TCP/IP	B-Protocol
protocol	I-Protocol
stack	I-Protocol
.	O
</s>
<s>
This	O
programming	O
was	O
typically	O
done	O
in	O
assembly	B-Language
language	I-Language
,	O
or	O
sometimes	O
in	O
C	B-Language
or	O
PL/M	B-Language
,	O
and	O
then	O
cross-assembled	O
or	O
cross-compiled	B-Application
on	O
the	O
host	O
.	O
</s>
<s>
Some	O
single-board	B-Device
microcontrollers	I-Device
support	O
a	O
BASIC	O
language	O
system	O
,	O
allowing	O
programs	O
to	O
be	O
developed	O
on	O
the	O
target	O
hardware	O
.	O
</s>
<s>
Early	O
microcontrollers	B-Architecture
relied	O
on	O
erasable	B-General_Concept
programmable	I-General_Concept
read-only	I-General_Concept
memory	I-General_Concept
(	O
EPROM	B-General_Concept
)	O
devices	O
to	O
hold	O
the	O
application	O
program	O
.	O
</s>
<s>
The	O
object	B-Language
code	I-Language
from	O
a	O
host	O
system	O
would	O
be	O
"	O
burned	O
"	O
onto	O
an	O
EPROM	B-General_Concept
with	O
an	O
EPROM	B-General_Concept
programmer	I-General_Concept
.	O
</s>
<s>
This	O
EPROM	B-General_Concept
was	O
then	O
physically	O
plugged	O
into	O
the	O
board	O
.	O
</s>
<s>
As	O
the	O
EPROM	B-General_Concept
would	O
be	O
removed	O
and	O
replaced	O
many	O
times	O
during	O
program	O
development	O
,	O
it	O
was	O
common	O
to	O
provide	O
a	O
ZIF	B-General_Concept
socket	I-General_Concept
to	O
avoid	O
wear	O
or	O
damage	O
.	O
</s>
<s>
Erasing	O
an	O
EPROM	B-General_Concept
with	O
a	O
UV	B-Application
eraser	O
takes	O
a	O
considerable	O
time	O
,	O
and	O
so	O
it	O
was	O
also	O
common	O
for	O
a	O
developer	O
to	O
have	O
several	O
EPROMs	B-General_Concept
in	O
circulation	O
at	O
any	O
one	O
time	O
.	O
</s>
<s>
Some	O
microcontroller	B-Architecture
devices	O
were	O
available	O
with	O
on-board	O
EPROM	B-General_Concept
.	O
</s>
<s>
The	O
use	O
of	O
EPROM	B-General_Concept
sockets	O
allowed	O
field	O
updates	O
to	O
the	O
application	O
program	O
,	O
either	O
to	O
fix	O
errors	O
or	O
to	O
provide	O
updated	O
features	O
.	O
</s>
<s>
When	O
the	O
single-board	O
controller	O
formed	O
the	O
entire	O
development	O
environment	O
(	O
typically	O
in	O
education	O
)	O
,	O
the	O
board	O
might	O
also	O
have	O
included	O
a	O
simple	O
hexadecimal	O
keypad	O
,	O
calculator-style	O
LED	O
display	O
,	O
and	O
a	O
"	O
monitor	O
"	O
program	O
set	O
permanently	O
in	O
ROM	B-Device
.	O
</s>
<s>
This	O
monitor	O
allowed	O
machine	B-Language
code	I-Language
programs	O
to	O
be	O
entered	O
directly	O
through	O
the	O
keyboard	O
and	O
held	O
in	O
RAM	B-Architecture
.	O
</s>
<s>
These	O
programs	O
were	O
in	O
machine	B-Language
code	I-Language
,	O
not	O
even	O
in	O
assembly	B-Language
language	I-Language
,	O
and	O
were	O
often	O
assembled	O
by	O
hand	O
on	O
paper	O
before	O
being	O
inputted	O
.	O
</s>
<s>
Single-board	O
"	O
keypad	O
and	O
calculator	O
display	O
"	O
microcontrollers	B-Architecture
of	O
this	O
type	O
were	O
very	O
similar	O
to	O
some	O
low-end	O
microcomputers	O
of	O
the	O
time	O
,	O
such	O
as	O
the	O
KIM-1	B-Device
or	O
the	O
Microprofessor	B-Device
I	I-Device
.	O
</s>
<s>
Some	O
of	O
these	O
microprocessor	B-Architecture
"	O
trainer	O
"	O
systems	O
are	O
still	O
in	O
production	O
today	O
,	O
used	O
as	O
very	O
low-cost	O
introductions	O
to	O
microprocessors	B-Architecture
at	O
the	O
hardware	O
programming	O
level	O
.	O
</s>
<s>
When	O
desktop	O
personal	O
computers	O
appeared	O
,	O
initially	O
CP/M	B-Application
or	O
Apple	B-Device
II	I-Device
,	O
then	O
later	O
the	O
IBM	B-Device
PC	I-Device
and	O
compatibles	O
,	O
there	O
was	O
a	O
shift	O
to	O
hosted	O
development	O
.	O
</s>
<s>
Hardware	O
was	O
now	O
cheaper	O
and	O
RAM	B-Architecture
capacity	O
had	O
expanded	O
such	O
that	O
it	O
was	O
possible	O
to	O
download	O
the	O
program	O
through	O
the	O
serial	B-Protocol
port	I-Protocol
and	O
hold	O
it	O
in	O
RAM	B-Architecture
.	O
</s>
<s>
This	O
program	B-Device
memory	I-Device
was	O
still	O
volatile	B-General_Concept
and	O
would	O
be	O
lost	O
if	O
power	O
was	O
lost	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
was	O
not	O
yet	O
available	O
at	O
a	O
viable	O
price	O
.	O
</s>
<s>
As	O
a	O
completed	O
controller	O
project	O
was	O
usually	O
required	O
to	O
be	O
non-volatile	O
,	O
the	O
final	O
step	O
in	O
a	O
project	O
was	O
often	O
to	O
burn	O
it	O
to	O
an	O
EPROM	B-General_Concept
.	O
</s>
<s>
Single-chip	O
microcontrollers	B-Architecture
,	O
such	O
as	O
the	O
Intel	O
8748	B-Device
,	O
combined	O
many	O
of	O
the	O
features	O
of	O
previous	O
boards	O
into	O
a	O
single	O
IC	O
package	O
.	O
</s>
<s>
Single-chip	O
microcontrollers	B-Architecture
integrate	O
memory	O
(	O
both	O
RAM	B-Architecture
and	O
ROM	B-Device
)	O
on-package	O
and	O
,	O
therefore	O
,	O
do	O
not	O
need	O
to	O
expose	O
the	O
data	O
and	O
address	O
bus	B-General_Concept
through	O
the	O
pins	O
of	O
the	O
IC	O
package	O
.	O
</s>
<s>
These	O
pins	O
are	O
then	O
available	O
for	O
I/O	B-General_Concept
lines	O
.	O
</s>
<s>
These	O
changes	O
also	O
reduce	O
the	O
area	O
required	O
on	O
the	O
printed	O
circuit	O
board	O
and	O
simplify	O
the	O
design	O
of	O
the	O
single-board	B-Device
microcontroller	I-Device
.	O
</s>
<s>
Examples	O
of	O
single-chip	O
microcontrollers	B-Architecture
include	O
:	O
</s>
<s>
For	O
production	O
use	O
as	O
embedded	B-Architecture
systems	I-Architecture
,	O
the	O
on-board	O
ROM	B-Device
was	O
either	O
mask	B-General_Concept
programmed	I-General_Concept
at	O
the	O
chip	O
factory	O
or	O
one-time	O
programmed	O
(	O
OTP	O
)	O
by	O
the	O
developer	O
as	O
a	O
PROM	B-General_Concept
.	O
</s>
<s>
PROMs	O
often	O
used	O
the	O
same	O
UV	B-General_Concept
EPROM	I-General_Concept
technology	O
for	O
the	O
chip	O
,	O
but	O
in	O
a	O
cheaper	O
package	O
without	O
the	O
transparent	O
erasure	O
window	O
.	O
</s>
<s>
During	O
program	O
development	O
,	O
it	O
was	O
still	O
necessary	O
to	O
burn	O
EPROMs	B-General_Concept
.	O
</s>
<s>
In	O
this	O
case	O
,	O
the	O
entire	O
controller	O
IC	O
,	O
and	O
therefore	O
the	O
ZIF	B-General_Concept
sockets	I-General_Concept
,	O
would	O
be	O
provided	O
.	O
</s>
<s>
With	O
the	O
development	O
of	O
affordable	O
EEPROM	B-General_Concept
and	O
flash	B-Device
memory	I-Device
,	O
it	O
became	O
practical	O
to	O
attach	O
the	O
controller	O
permanently	O
to	O
the	O
board	O
and	O
to	O
download	O
program	O
code	O
from	O
a	O
host	O
computer	O
through	O
a	O
serial	O
connection	O
.	O
</s>
<s>
This	O
was	O
termed	O
"	O
in-circuit	B-Device
programming	I-Device
"	O
.	O
</s>
<s>
Erasure	O
of	O
old	O
programs	O
was	O
carried	O
out	O
by	O
either	O
over-writing	O
them	O
with	O
a	O
new	O
download	O
,	O
or	O
bulk	O
erasing	O
them	O
electrically	O
(	O
for	O
EEPROM	B-General_Concept
)	O
.	O
</s>
<s>
The	O
main	O
function	O
of	O
the	O
controller	O
board	O
was	O
then	O
to	O
carry	O
the	O
support	O
circuits	O
for	O
this	O
serial	O
or	O
,	O
on	O
later	O
boards	O
,	O
USB	B-Protocol
interface	O
.	O
</s>
<s>
As	O
a	O
further	O
convenience	O
during	O
development	O
,	O
many	O
boards	O
also	O
had	O
low-cost	O
features	O
like	O
LED	O
monitors	O
of	O
the	O
I/O	B-General_Concept
lines	O
or	O
reset	O
switches	O
mounted	O
on	O
board	O
.	O
</s>
<s>
It	O
is	O
now	O
cheap	O
and	O
simple	O
to	O
design	O
circuit	O
boards	O
for	O
microcontrollers	B-Architecture
.	O
</s>
<s>
Development	O
host	O
systems	O
are	O
also	O
cheap	O
,	O
especially	O
when	O
using	O
open	B-Application
source	I-Application
software	I-Application
.	O
</s>
<s>
Higher	O
level	O
programming	O
languages	O
abstract	B-Application
details	O
of	O
the	O
hardware	O
,	O
making	O
differences	O
between	O
specific	O
processors	O
less	O
obvious	O
to	O
the	O
application	O
programmer	O
.	O
</s>
<s>
Rewritable	O
flash	B-Device
memory	I-Device
has	O
replaced	O
slow	O
programming	O
cycles	O
,	O
at	O
least	O
during	O
program	O
development	O
.	O
</s>
<s>
Accordingly	O
,	O
almost	O
all	O
development	O
now	O
is	O
based	O
on	O
cross-compilation	B-Application
from	O
personal	O
computers	O
and	O
programs	O
are	O
downloaded	O
to	O
the	O
controller	O
board	O
through	O
a	O
serial-like	O
interface	O
,	O
usually	O
appearing	O
to	O
the	O
host	O
as	O
a	O
USB	B-Protocol
device	O
.	O
</s>
<s>
The	O
original	O
market	O
demand	O
for	O
a	O
simplified	O
board	O
implementation	O
is	O
no	O
longer	O
as	O
relevant	O
for	O
microcontrollers	B-Architecture
.	O
</s>
<s>
Single-board	B-Device
microcontrollers	I-Device
are	O
still	O
important	O
,	O
but	O
have	O
shifted	O
their	O
focus	O
to	O
:	O
</s>
<s>
These	O
controllers	O
may	O
be	O
embedded	O
to	O
form	O
part	O
of	O
a	O
physical	B-General_Concept
computing	I-General_Concept
project	O
.	O
</s>
<s>
Popular	O
choices	O
for	O
this	O
work	O
are	O
the	O
Arduino	O
,	O
Dwengo	O
or	O
Wiring	B-Device
.	O
</s>
