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bendembarrassElectronics - Devices

Nov 2, 2013 (3 years and 5 months ago)

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Gadget Lab Lecture 6:

Sensors and Interfacing…

Microcontrollers…

More
Project Time

Dr. Cindy Harnett

ECE Dept., U of Louisville

Spring 2008

Course Evals

Microcontrollers

run the gadget universe






A
MSP430

microcontroller talks to the 1
-
wire chips in the
sensor project, and to the radio chip. (Texas Inst.)


ARM

microcontrollers in cell phones are as powerful as
desktop computers of a few years ago, and consume little
power. (Made by many companies)


Nowadays: programmable in high level languages like C.


Minimalist chips like some
PIC

microcontrollers
(Microchip) are still programmed in assembly language.


Most microcontrollers are not good at multitasking, but
excel at repetitive tasks requiring good timing.



Remember all those “black dots” in our
teardowns? Usually there’s a microcontroller
underneath. Sometimes a custom made IC.

Microchip PICs

ARM

Furby board

MSP430

Assembly Language

Strict syntax, few commands

Commands differ for each controller

Can make up variable names

Can have subroutines

Should have comments!

;
--------

; change LED pattern based on state of digit_index and dot_index

;
--------

Display_now

movlw

0x05



xorwf

dot_index,w

;test for end of digit



movlw

0xFF


;pattern for blank column



btfsc

STATUS,Z



goto

D_lookup_3

;it needs a blank



bcf

STATUS,C

;clear carry before a rotate



rlf

digit_index,w

;double the index because each



addwf

PCL,f


;takes two instructions

How do you program
microcontrollers?


Get or build a
programmer

that plugs into a
PC. Can program in a ZIF socket or in a circuit.


Get software that “
cross
-
compiles
” from your
PC to the target chip. Usually sold by the chip
maker, sometimes 3rd party


Usually there’s a free
development
environment

that lets you code, compile, and
download your code onto the chip


Fancy hardware (debuggers, emulators) is
usually available to catch
run
-
time errors
.

Learning to use microcontrollers


Take ECE course specifically on microcontrollers:




Or pick a starter project like lighting a 7
-
segment
display and learn from examples


Microchip PICs are versatile and cheap
--
if you
stick with assembly language
--
http://www.phanderson.com



MSP430 tools are also inexpensive ($20
-
$40)


Or get a module like a Basic Stamp or Arduino,
with a large online community and plenty of code


ECE 412, Computer Interfacing (uses 68HC11 chips)


From last time:

Computer Interfacing


LabView PCI or PCMCIA
cards and connector board
very common in research labs

http://www.ni.com



Lower cost: “Phidgets” have
analog inputs and USB to PC

http://www.phidgets.com



Even cheaper, dedicated
circuits such as the 1
-
Wire
DS2450 converter

http://www.maxim
-
ic.com


And many more…

Demos based on lab projects at U of L:


1
-
Wire and wireless sensor interfacing

“1
-
wire” chips allow
multiple sensors to be
connected to the same
wire for weatherstations
and similar devices.

(Thermometer Demo)

http://www.maxim
-
ic.com/products/1
-
wire/

Wireless sensor board
can poll multiple sensors
on the 1
-
wire bus.

(Flow sensor demo)

From last time:

Antepenultimate* Slide of the
Entire Semester


Thanks for being the Gadget Lab “
guinea
pigs
.” Comments? What should be changed
next year?


See IEEE student group for jumper
wires/other gadget building tools.


Slides and most websites I mentioned in the
course are available on BlackBoard.


Visit ECE labs in BRB/Lutz/Speed!

*2 more slides after this one. This word is “drittletzt” in German

Soldering “Tips”



Heat the part, then solder will flow onto it. If solder is only going onto your
wire but not your motor, you’ve probably noticed that thin wires heat more
quickly than chunky motors. Try heating the motor first, then bring the wire
in just before soldering.


Attach copper foil to your motor: copper solders easily


Is the tip blackened (oxidized) so much that

the solder won’t melt? Dip the hot soldering

iron in tip
-
tinner.


Avoid touching the soldering iron to the sponge for more than about 1
second. Long contact will oxidize the tip.


Work at the lowest temperature you can, to avoid oxidizing the tip.


Sandpaper can be used in tough cases (let your tip cool off first), but
eventually it will remove the tin plating on the iron.


You will need a new tip someday.





Feb. 16:
Engineering Day

at the


727 West Main Street


12:30
-
4:30 (drop in anytime)


Show off your projects at the ECE table



Project Time!

And A Special Announcement
--