The sensor$$s output voltage can be digitized with one of the ADC channels in the MCU. The ADC has a

maximum of $14$ bits of resolution, providing $16,384$ levels of voltage digitization. The reference voltage is

provided by the voltage reference module in the MCU. The module provides three selections of voltages: $1\mathrm{.}2,$

$1\mathrm{.}45$ and $2\mathrm{.}5$ V$.$ For example, if $2\mathrm{.}5$ V is used, the ADC provides a resolution of $0\mathrm{.}15$ mV $(2\mathrm{.}5/16384)$

The example project,

C:$\backslash$ti$\backslash$simplelink$\_$msp$432$p$4\_$sdk$\_3\_40\_01\_02\backslash$examples

ortos$\backslash$MSP$\_$EXP$432$P$401$R$\backslash$driverlib$\backslash$adc$14\_$single

$\_$conversion$\_$repeat$\_$timera$\_$source$\backslash$ccs$,$ illustrates how to set up various modules to do the timer triggering.

Basically, it sets up the A$0$ timer to count in Up mode and Compare register $1($TA$0$CCR$1)$ to generate a

pulse train to trigger an ADC sampling on the rising edge of a pulse.

Use the previous project and the example project, and adapt accordingly, to produce the same results in the

previous exercise. Note that the example project uses ADC input channel A$0,$ but the temperature sensor

uses A$22.$ Define the sampling frequency to use with following statement:

#define SAMPLING$\_$FREQUENCY $100//$ Sampling frequency in Hz

Compute the necessary parameters in the program based on this constant and the current frequency of the

system $($do not hard$-$code the system clock frequency or its period$).$ For more precise timing, use SMCLK

$($not ACLK$)$ for the timer module setup. The duty cycle of the pulse train is not important here. So$,$ use

something reasonable.

Do not enter sleep mode in the control loop in main$()($as it is done in the example project$).$ There is no

triggering action in the control loop because it is now all done by the timer. Since we are sampling at a much

higher rate than the rate to print to the console, the ISR can just update a global variable to contain the latest

digitized value, and the control loop just uses it when needed.

Before the control loop is entered, do a quick measurement on the sampling frequency to verify that the ADC

is indeed sampling at the desired rate. For example, we can measure how long it takes to collect $10$ samples

with the Timer$32$ timer. Print the measured frequency to the debug console. If the measurement is

implemented properly, the measured frequency should be very close to the defined macro

SAMPLING$\_$FREQUENCY because the timing is all controlled by hardware; the error should be less than

$0\mathrm{.}01$ Hz$.$ Note that there are two software $$tasks$$ going on at the same time here. One is the ISR being

invoked periodically to update the global variable containing the latest digitized value, and the other is main$()$

doing the measurement. In order to measure the sampling rate accurately, we need to pay attention to when

the digitization cycle starts or ends.

After the quick measurement is done, enter the forever control loop to show the digitized value and voltage

at a regular interval. Note that the display frequency in the control loop $($the foreground task$)$ is much lower

than the sampling $($the background task$)$ frequency.

Do not use the MAP$\_$Interrupt$\_$enableSleepOnIsrExit$()$ call in your program as it is done in the example

project so that the control loop in main$()$ can continue to run after an interrupt is processed. Also do not use

MAP$\_$CS$\_$initClockSignal$()$ as it will change SMCLK to a much lower value.