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The F5637's ADC can run off of one of several available clock signals of varying speeds. Once a sample has been captured, it is held ready in the ADC10MEMx registers for a defined number of clock cycles. Since we are concerned with a low frequency signal, we will want to slow down the ADC12 as much as possible. (Students who have had Elec241 will notice some fundamental flaws in the assumptions made regarding high-frequency noise, but in practice this has very little effect on the final results). Even in its slowest mode, the ADC12 will still sample too quickly, so the use of some kind of moving average will help stabilize its DC readings.

Controlling the adc12 in c

C basics

Your C program will be structured similarly to its assembly language counterparts, but with a much different syntax. Like before, the register names are all pre-defined in the "msp430.h" header file. To set a register, now just use an equals sign and set it like any other variable. For example, you will want to disable the watchdog timer in the first line of your program. WDTCTL=WDTPW+WDTHOLD; The compiler will execute the void main(void) function first. From that function, you can call any other functions or run any loops that you would like.

C skeleton program

#include<msp430.h>//Global Variable Declarations //Global Function Declarationsint main(void) {WDTCTL = WDTPW + WDTHOLD; // Stop WDT //Other Setup//Your Program Here //Can call other helper functions, loops, etc.return 0; }

Configuring the adc12

The ADC12 has two main control registers ADC12CTL0 and ADC12CTL1 , and 16 memory control registers ADC10MCTLx ( 12 bit ADC M emory C o N tro L 0/1/2... channel 0-15). These registers control all the timing and conversion aspects of the ADC.

Adc12ctl0

Register diagram of the ADC12CTL0 register.

In the first control register ( ADC12CTL0 ), we only need to change two parameters,

  • ADC12SHT0_x-- 12 bit ADC S ample H old T ime-- a higher value means each sample will be held for a longer period of time. We want to set this at the max value of ADC12SHT0_8 .
  • ADC12ON-- 12 bit ADC ON /OFF--setting this bit to "1" (denoted by the label ADC12ON ) turns on the ADC, a vital step to performing any conversion!
To actually do this in C, just use addition and an equals sign: ADC12CTL0 = ADC12SHT0_8 + ADC12ON ;

Adc12ctl1

Register diagram of the ADC12CTL1 register.

In the second control register ( ADC12CTL1 ), we want to set two parameters.

  • Since some of the bit labeling is inconsistent (especially between different versions of a microcontroller), it is always good to examine the header file for a controller to see how its aliases are defined before using them in your code.
ADC12CTL1 = ADC12SHP + ADC12CONSEQ_0;

Register diagram of the ADC12CTL1 register.

We also need to set the appropriate input channel to our output memory address in the ADC12MCTL0 register

  • ADC12INCH_x-- 12 bit ADC In put Ch annel # -- this 4 bit section determines which of the possible input channels the ADC will actually convert and store into the ADC12MEM0 register.
ADC12MCTL|= ADC12INCH_0;

Lastly, analog conversion must be enabled on the input ports themselves. These act as gates to prevent leakage current from flowing from a pin set as an output through the ADC to ground-- a substantial waste of power. To enable the ADC for your desired GPIO pin, just set the corresponding bit in P6SEL ( P ort 6 Special Function SEL ect) to "1". P6SEL |= BIT#;

For more info about the ADC12's configuration options, see the MSP430 manual starting on page 742.

Using the adc

To read a sample from the ADC, just read from the ADC12MEM register after the sample has completed. while (ADC12CTL1&ADC12BUSY); // Wait in naive loop for conversion to complete my_var= ADC12MEM0; Remember that we have setup the ADC for single conversion and hold, so if you want another value, you will have to tell it to sample and convert again. You do so by modifying two values in ADC12CTL0:

  • ADC12ENC-- 12 bit ADC En able C onversion-- locks in the ADC settings and stabilizes it for conversion.
  • ADC12SC-- 12 bit ADC S tart C onversion-- setting this bit to one actually triggers the ADC's conversion cycle.
ADC12CTL0 |= ADC12ENC + ADC12SC;
Be sure to use OR equal (|=) so that the configuration bits you set before don't get overridden.
Also, don't forget to configure P3 as usual. You will need to set the pins you wish to use as outputs in the P3DIR register to display a value on the LEDs. You can configure the P3 registers using aliases and variable assignments just like with the ADC registers.

Assignment details

Using Code Composer Studio 5, write a C language program turning your MSP430 ESCAPE Platform into a simple 10 level voltmeter. Your program should divide the 0-3.3V input range of the ADC into 10 zones, and then output from a 0 to a 9 on the LED display depending on the input voltage from the light sensor. Don't worry about a value landing on the boundary between two zones, just deal with it consistently. Test your volt meter by sampling pin P6.0 and exposing it to different light intensities.

Your Program should consist of:

  • A "void main(void)" function that drives your program
  • A successful setup routine that properly configures the ADC12
  • An output routine that loop infinitely and successfully re-scales the 4096 ADC possibilities to 10 zones

Questions & Answers

how environment affect demand and supply of commodity ?
Amos Reply
Wht at the criteria for market ?
Amos
what is difference between monitory policy and fiscal policy?
Malik Reply
monetary policy is a policy thrust by National Govt(CBN) to influence government spending, purchase &taxes
Frank
necessity of economics
Pamela Reply
I will say want,choice,opportunity cost,scarcity,scale of preference
Alao
what is monopoly market.How price output are determined under monopoly market
bisham
b) Monopoly market is an impecfect market where s single firm having the innovation to produce a particular commodity.Prices are determined through output since there are no other competitive.
Frank
Monopoly market:firm has market power & does not respond to market price
Frank
Explain the process of price determination under perfect competition market with suitable diagram
bisham Reply
Price determination under perfect competition via this process :firms have no market power to influence price rather firms respond to market price.
Frank
price is different from demand- demand is amount of commodity
Effah Reply
demand is amount /quantity of commodity a potential buyer is willing to buy at a given price at market
Frank
demand is a desire of customer on commodity with the ability to pay it and willing to buy it at given price of commodity
Harika
demand is price of what
Faith Reply
show that shortrun average cost
Baby Reply
what is economics
Mbah Reply
what is money
Mbah
what is money
Mbah
Difine macro economics
agaba
money is a medium of exchange between goods and services,maybe inform of currency.
Wesonga
Economics is study of how human beings strive to satisfy numerous wants using limited available resources.
Wesonga
how do you find the maximum number of workers the firms should employ order to produce where there are increasing returns
Jane
what are implications of computing national income?.
agaba
pl
MUDASIRU
what is the formulae for calculating national income
MUDASIRU
it calculated by value added method
Praveen
classify the production units like agriculture, banking, transport etc
Praveen
money is anything that is generally acceptetable for human
Ogbaji
Estimate the net value added(NVA) at fixed cost by each industrial structure
Praveen
definition of unemployment
Adam Reply
what are the causes of unemployment?
Mbubi Reply
The main causes of unemployment are listed below. 1. Frictional unemployment 2. Cyclical unemployment 3. Structural unemployment
assani
We can also categorize the causes on a broader sense as: 1. Political and 2. Social cause As unemployeement root causes are embaded in this two.
Yonathan
would opportunity cost exist if there was no scarcity?
assani
yes just because the opportunity cost arose when there is Alternative to choose among the alternatives.
BADAMASIU
I am thinking that, if our resources were unlimited, then there wouldn't be any need to forgo some wants. Hence the inexistence if opportunity cost
assani
Politics
Job
politics has done what?
assani
consider time assani
Mary
I'm Emmanuel,...I taught the main cause is the change in gov't.
Emmanuel
...Lack of capital to set up a firm respectively
Emmanuel
🙈
Emmanuel
I would like to bring in Educational levels can also be the cause the cause of the problem respectively
Emmanuel
I think the main causes of unemployment is lack of INFRASTRUCTURAL DEVELOPMENT OVER POPULATION OVER DEPENDENT ON GOVERNMENT LACK OF SELF EMPOWERMENT...
ananti
lack of skills among the new generation is the serious issue.
Vishal
Where I come from , I don't see why education or personal aspects seem to do with unimployment, technically the motivation and eigerness in all works of live is there , dispite the cultural influence and physical bearriors;the thing we lacking is Government Support and open market ethics.
Joe
sorry about that-(repation). We have a over powering ethical political system that's displacing the marketing asspects of economy and causing large scale unemployment right across the board...
Joe
can someone Explain Expansionary Monetary Policy and Contractionary Monetary Policy Using one of the instrument of Monetary Policy? Please am kinda lost here?. ta
Emmanuel Reply
using a graph show the case of substitute and compliment goods
Ade Reply
can anyone give me a simple explanation to Five Sector Macroeconomics?
Emmanuel
Can someone please define what economics is
jason Reply
economics simply is a social science subject that study human behavior.
dajan
economics is a social science which studies human behaviour as a relationship between ends and scarce means that has alternative uses
Alao
Can someone please tell me how to calculate GDP
Emmanuel
emmanual kapal to calculate GDP (Gross Domestic Product) has three method in calculating it (1)income approach (2) expenditure approach (3) value added method
Alao
thanks Alae
Emmanuel
u are welcome
Alao
in basic terms economics is revered to as battery system, it date back to when Men sees the need to exchange sapless goods and produce to gain , either wealth , basic necessities or to establish trading ties for personal benefit or social asspects in terms of coexistence and continuity, future .
Joe
what is the law of demand
Berlinda Reply
keep other thing constant, when the price increases demand decrease when the price decreases demand increases of the commodity.
sj
all things being equal,quantity demanded decrease as price increase and increase as price decrease
Seth
there's practial joke to it ..." the higher the demand ; scarcity, increase in production and drop in quality"... quite the controversy - for example China vs Europe, United States and we are all boxed up in between somewhere...
Joe
Other thing remain constant the low price of commodity the high quantity of commodity and vice versa is true
Baraka
Explain Effective demand
Anita Reply
What is effective demand
Anita
like Modi is in demand...best example of effective demand
Pranav
Don't get you
Anita
Anita you mean you don't get me or who?
Onyeking
level of demand that represents a real intention to purchase by people with the means to pay
Pranav
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Source:  OpenStax, Elec 220 lab course (escape). OpenStax CNX. Apr 07, 2013 Download for free at http://cnx.org/content/col11513/1.1
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