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Explains how the digital-to-analog converter works on the MSP430.

The MSP430F169 is equipped with two digital to analog converters (DACs) on general I/O port 6. A DAC converts an unsigned integer into an analog voltage within the capacity of the MSP. As in all cases with the MSP, the complete details are found in the MSP430 Family User’s Guide from the Texas Instruments website www.ti.com .

Voltage range and precision

Unlike the ADC on the MSP, the DACs have variable bit precision of either 8 or 12 bits. The range is also controllable as either one or three times the voltage reference. The voltage reference is also selectable. All bits for controlling voltage reference, scaling, and precision can be found in the DAC12 Control Register (DAC12_xCTL). In most cases, 12 bit precision is desirable.

In the MSP430 architecture there are two general sources for a voltage reference: VeRef and Vref. VeRef is an externally supplied voltage, but Vref is generated by the MSP itself. Because the 226 board does not provide the MSP with a VeRef voltage, the only voltage reference available for the DAC and ADC is the Vref. This restricts the choices for the SREF bits of the DAC control register to the Vref choice. Additionally, the Vref voltage reference for the DAC comes from the ADC module. This means that it is necessary to turn on the voltage reference in the ADC control register (ADC12CTL0) with the REFON bit.

Operating modes

The DAC competes with two of the ADC channels for access to the pins of I/O Port 6. Unlike most peripheral controls on the MSP430, the DAC’s access to the pins is not controlled by the PxSEL register. Instead, the DAC is multiplexed with the ordinary port control and will drive the output if the DAC12AMPx bits are set to any value greater than zero. The DAC12AMPx bits in the control registers also determine the mode of the DAC’s operation.

  • Mode 000 The input buffer is off. The DAC is off, and the output buffer is high impedence.
  • Mode 001 The input buffer is off. The DAC is off, and the output buffer is 0V.
  • Modes 010 - 111 Each step in mode increases the power consumption of the DAC while improving the settling time of the module.
The two most useful modes for these labs are modes 000 and 111. Because our devices are not battery powered, we can afford the power consumption to improve speed. Mode 000 is needed to turn off the module when necessary.

Using the dac

The basic method of DAC operation is to load the DAC12_xDAT. Using the DAC12LSELx bits of the control register, the actual trigger for the output is set. The device can be figured to output whenever the data register is written to, whenever the data register is written and the DAC enable is set, or according to timers A or B. It is necessary to change the mode out of SEL mode 0 in order to use the interrupts with the DAC.

The DAC can be interrupt enabled via the DAC control register and the interrupt enable registers. The flag is set whenever a conversion is complete. Also, the DAC outputs can be grouped together to ensure that the output of both DACs appears simultaneously. When the units are grouped, both DAC12_xDAT registers must be written before the outputs will appear. The device does not check whether you have changed the value; updating with the same information will still work.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
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
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Microcontroller and embedded systems laboratory. OpenStax CNX. Feb 11, 2006 Download for free at http://cnx.org/content/col10215/1.29
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