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Calibration

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

how can chip be made from sand
Eke Reply
are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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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