Tinkering TI MSP430F5529

Analogue Hardware Overview

Except Digital-to-Analog Converter (DAC), MSP430F5529 microcontroller offers two major analogue hardware peripherals – ADC12_A and Comp_B+. Additionally, there is an on-chip reference voltage generator called REF module that can generate pretty accurate voltage references – 1.5V, 2.0V and 2.5V reference voltages.

As the name suggests ADC12_A is a fast 12-bit Analogue-to-Digital Converter (ADC). Since it has higher resolution compared to other typical 8-bit and 10-bit ADCs of other microcontrollers, it much more precise when it comes to reading analogue voltages. MSP430s usually pack SAR ADCs and the ADC12_A of MSP430F559 is a 200+ ksps Successive Approximation (SAR) ADC. ADC12_A has an internal temperature sensor and REF module’s reference voltages can be used with ADC12_A for more precise measurements. It is also possible to use external sources. Positive and negative references can be independently selected. Sample-and-hold circuitry offers programmable sampling periods via timers or software. In MSP430F5529, there are 16 individually configurable input channels – 12 external input channels and 4 internal input channels. There also 16 buffer registers to store AD conversion data. Since MSP430F5529 hosts a Direct-Memory-Access (DMA) peripheral, it can be combined with ADC12_A and we can get some more interesting effects.

A comparator compares two analogue voltage levels. This comparison results in an indication of which signal is at a higher/lower voltage level than the other. In simple terms, it is a one-bit ADC. Though it may look that a comparator is unnecessary when we have a good built-in ADC, it is otherwise. A comparator is a very important analogue building block. It is helpful in places where knowing voltage levels is more important the voltage itself. This makes it faster than an ADC in such cases. Owing to this a whole lot of electronics is based on it. Examples of such electronics include oscillators, level sensing, VU meters, capacitive touch sensing, measurement devices, etc. A LC meter is a perfect example. A LC meter is usually based on an oscillator. This oscillator uses a comparator. Its frequency varies with the L and C components, oscillating at a fixed frequency with known L and C values. Measuring frequency shifts as a result of changing L/C values leads us to measure unknown L/C effectively.

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