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Using the MSP-EXP430FG4618 Development Tool analyse the Comparator_A operation. A voltage is applied to one of the Comparator’s inputs, generated optionally by the DAC12 or by other external source. Whenever the external voltage value is higher than the comparison value internally generated, it is generated an interrupt that switches the LED state.

Laboratory signal acquisition: lab4 - voltage signal comparison with comparator_a


This laboratory gives examples of the uses of the ADC types available in the hardware development kits. A different laboratory is developed for each kit, taking into account that both the ADC10 and the SD16_A laboratories implement a temperature data logger. The ADC12 laboratory also uses operational amplifiers to perform the analogue signal conditioning.


This laboratory ( Lab4_ADC.c ) analyses Comparator_A operation. A voltage is applied to one of the Comparator’s inputs, generated either by the DAC12 or by other external source. Whenever the external voltage value is higher than the comparison value internally generated, an interrupt is generated that switches the LED state.


The resources used by the application are:

- DAC12;

- Comparator_A;

- Digital IO;

- Timer_A.

Software application organization

The application starts by stopping the Watchdog Timer.

Timer_A is configured to generate an interrupt once every msec, and updates the DAC12 output in order to provide a ramp signal.

The Comparator_A’s output is configured to be accessible at pin P6.6, which is available on Header 4 pin 7. The signal applied to CA0 input is compared with 0.5 V cc internal reference voltage. Every time that a compare match occurs, an interrupt is requested and switches the state of LED1.

System configuration

Comparator_a configuration

Configure the registers in order to receive the external signal at the CA0 input and compare it with the internal reference 0.5 V cc . Enable the comparator with an interrupt triggered on a low-to-high transition of the comparator output.

CACTL1 = CAON | CAREF_2 | CARSEL | CAIE; // Enable comp, ref = 0.5*Vcc CACTL2 = P2CA0; // Pin to CA0P2DIR |= 0x042; // P2.1 and P2.6 output direction P2SEL |= 0x040; // P2.1 = LED1 and P2.6 = CAOUTCACTL1 |= CAIE; // Setup interrupt for Comparator //*********************************************************// Comp_A interrupt service routine -- toggles LED //*********************************************************#pragma vector=COMPARATORA_VECTOR __interrupt void Comp_A_ISR (void){ CACTL1 ^= CAIES; // Toggles interrupt edgeP2OUT ^= 0x02; // Toggle P2.1 }

Adc12 configuration

ADC12CTL0 = REF2_5V + REFON; // Internal 2.5V ref on

Dac12 configuration

DAC12_0DAT = 0x00; // DAC_0 output 0V

DAC12_0CTL = DAC12IR | DAC12AMP_5 | DAC12ENC; // DAC_0->P6.6 // DAC reference Vref// 12 bits resolution // Imediate load// DAC full scale output // Medium speed/current// Straight binary // Not grouped

Timer_a configuration

// Compare mode TAR = 0; // TAR resetTACCR0 = 13600; // Delay to allow Ref to settle TACCTL0 |= CCIE; // Compare-mode interruptTACTL = TACLR + MC_1 + TASSEL_2; // up mode, SMCLK // Interrupt enableTAR = 0; // TAR reset TACCTL0 = CCIE; // CCR0 interrupt enabledTACCR0 = 32; // 1 msec counting period TACTL = TASSEL_1 | MC_1 | ID_0; // ACLK, up mode//********************************************************* // ISR to TACCRO from Timer A//********************************************************* #pragma vector=TIMERA0_VECTOR__interrupt void TimerA0_ISR (void) {DAC12_0DAT++; if (DAC12_0DAT == 0xFFF) DAC12_0DAT = 0;if (flag == 1) // if flag active exit LPM0{ flag = 0;LPM0_EXIT; }}

Analysis of operation

The experimental verification of this laboratory can be accomplished by connecting the DAC12’s output, available on Header 8 pin 7, to the Comparator_A’s input CA0, available on Header 4 pin 7.

Observe the signals wave form at the Comparator_A’s input and output using an oscilloscope. The LED1 switches state whenever the input’s voltage value is lower than the compare value.

This example and many others are available on the MSP430 Teaching ROM.

Request this ROM, and our other Teaching Materials here (External Link)

Questions & Answers

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..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
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.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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Source:  OpenStax, Teaching and classroom laboratories based on the “ez430” and "experimenter's board" msp430 microcontroller platforms and code composer essentials. OpenStax CNX. May 19, 2009 Download for free at http://cnx.org/content/col10706/1.3
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