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Like anything in the real world, your sensors and devices won't necessarily work perfectly all the time. Many analog semiconductor devices are light, temperature, and pressure sensitive, so your actual readings can vary depending on outside conditions. Also, while sensors are usually manufactured to within pretty tight tolerances, every sensor has some finite error that you will need to account for to get maximum performance.

Some kind of calibration routine can help alleviate many of these concerns. By calibrating your sensors against a trusted source, you can correct a lot of the skew caused by outside conditions. Calibration will also eliminate any steady state error caused by the device itself.

A calibration routine collects a set of known data points and scales the input signal to fit the calibration data. Since we are calibrating a linear ADC, we only need two data points to determine its operating curve. To get the most out of the calibration, you should use two data points that are as far from each other as possible. In the case of the MSP430 G2231, that is 0v and 3.3v .

Calibration routine pseudocode (not in c syntax)

flag=0; interrupt function: calibrate()returns: lowMeasured, highMeasured {if flag=0: set low and set flag=1if flag=1: set highreturn }

Interrupts in c

Code Composer Studio has a special way of handling interrupts in C. It uses "compiler directives" (special instructions to the compiler, assembler, and linker) to specify which functions should go in the interrupt vector table. ISRs in C are written like any other function, except that they can take and return no values. This fits with the convention that ISRs don't interfere with or depend on the code around them.

Formatting an interrupt in code composer c

#pragma vector=PORT1_VECTOR //compiler directive saying that this function should correspond with the port1 interrupt vector__interrupt void interruptHandle() {//your ISR CODE }void main() {... all setup __enable_interrupt();//Enables general maskable interrupts ... the rest of your program}

Other concerns

Even though interrupts should work in isolation, you often need to get or modify data inside them. This can be done using volatile global variables. A global variable simply means a variable that any function in your code can see and modify. Using global variables is generally discouraged (they can be easily abused and lead to problems if you repeat common variable names), but in this case they allow you to interface with your ISR. Volatile is a directive that tells the processor to never cache the variable's value. When dealing with ISRs, cached variables could lead to problems if the ISR updates the cached data while another function is using it. Be careful using the volatile keyword excessively though-- the lack of caching slows down performance.

Full range voltmeter assignment details

Using Code Composer Studio 4, write a C language program to drive a precise 3 digit volt meter. Use the ADC to read the voltage and display back the actual voltage value. Write a calibration routine for your volt meter and an output routine that will allow you to display each of the output digits.

    Your program should include:

  • A setup section to setup the GPIO, configure the ADC, and enable interrupts
  • An ISR that runs the calibration routine and keeps track of what has been calibrated so far (so it will only run once)
  • A main loop that continuously samples, filters, and scales the ADC input to the 0-3.3 volt range as determined by your calibration.

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Intro to computational engineering: elec 220 labs. OpenStax CNX. Mar 11, 2013 Download for free at http://cnx.org/content/col11405/1.2
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