This document summarizes code for a digital signal processing lab that uses a Tiva C Series microcontroller. The code includes header files for variable definitions, Boolean definitions, and APIs for the microcontroller, memory map, common types, and peripherals like system control, GPIO, and timers. Functions are declared to initialize LEDs and a timer. The timer is configured to generate interrupts at different frequencies by changing the TIMER0_FREQ definition, and an interrupt service routine toggles the LEDs.

1. Lab 2
EENG 3910: Project V - Digital Signal
Processing System Design
9/21/2015
Joseph Chandler
University of North Texas
College of Engineering
Electrical Engineering

2. Introduction
Lab 2 continuesthe studyof the TivaTM
C SeriesEK-TM4C123GXL andCCS software. Lab2 has software
driverlibrariesand typesof systemcontrols.The timingAPIandfrequencyare the mainaspectsof the
systemcontrolsanddifferentmodules.
Results and Discussions
Problem 1
#include <stdint.h>
Thisline containsthe headerfile forvariabledefinitions.The headerfileisalreadydefinedinthe CCS
software.Examplesof the valuesare bitsize,precision,andsignedorunsignedintegers.
#include <stdbool.h>
Thisline containsthe header file forBooleandefinitions.The headerfile isalreadydefinedinthe CCS
software The file definitionsare usedforoperations,comparingvariables,andprogramcontrol flow.
#include "inc/tm4c123gh6pm.h"
Thisline containsthe headerfile forthe TM4C123GH6PM microcontroller.The headerfile ispart-
specificandcontainsmacrosand definitionstosimplifyprogrammingthe peripheral'sregistersand
interruptcontrol.Thisiscontainedinthe incdirectory.The .c file forthe TM4C123GH6PM
microcontrollerisincludedinthe projectfolderfordirectaccess.
#include "inc/hw_memmap.h"
Thisline containsthe headerfile forthe TivaCSeriesdevice memorymapdefinitions.The headerfile
containsmanyof the same definitionsusedfordirectregisteraccess.The headerfilecontainsmacros
and definitionstosimplifyprogrammingthe peripheral'sregistersandinterruptcontrol.Thisis
containedinthe incdirectory.The definitionsare usedbydriverlibrariesandare hiddenfromthe
programmer.
#include "inc/hw_types.h"
Thisline containsthe headerfile forcommontypesandmacros.The headerfile containsmanyof the
same definitionsusedfordirectregisteraccess.Thisiscontainedinthe incdirectory.The definitionsare
usedbydriverlibrariesand are hiddenfromthe programmer.The valuesare a wide varietyof general
use for itemssuchas arithmetic,clocktiming,file recognition,anddevicerecognition.
#include "driverlib/sysctl.h"

3. Thisline containsthe headerfile forthe SystemControl API definitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The driversprovideguidedcontrol of the peripheralsand
allowsforquickapplication.Enablingperipheralsisanexampleof thiscontrol.
#include "driverlib/interrupt.h"
Thisline containsthe headerfile forthe SystemControl APIdefinitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The driversprovideguidedcontrol of the peripheralsand
allowsforquickapplication.Enablingperipheralsisanexampleof thiscontrol.
#include "driverlib/gpio.h"
Thisline containsthe headerfile forGPIOAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The driverprovidesasetof functionstocontrol the inputand output
module.
#include "driverlib/timer.h"
Thisline containsthe headerfile forTimerAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The driversprovide quickcontrol of the peripheralsandallowsforquick
application.The timerAPIprovidesasetof functionsforusingthe timermodule.
#define TIMER0_FREQ 10
Createsa constantusedfor frequencyinthe TimerAPImacrowitha value of 10 Hz.
void init_LEDs(void);
Thisline declaresthe functionprototype "init_LEDs".Declarationatthispointgivesthe actual functiona
global scope.Anyotherfunction,header,or.c file containedinthissource file isgivenaccesstothe
functionandaccessible bythe function.
void init_timer(void);
Thisline declaresthe functionprototype " init_timer".Declarationatthispointgivesthe actual function
a global scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccesstothe
functionandaccessible bythe function.
void Timer0_ISR(void);
Thisline declaresthe functionprototype " Timer0_ISR".Declarationat thispointgivesthe actual
functionaglobal scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccess
to the functionandaccessible bythe function.
uint32_t sys_clock;
Createsan unsigned32-bitglobal variable forthe systemclock.
int main(void){

4. The main processcallsandacts on variables,macros,definitions,andothersystemfunctions.
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
SystemControl ClockSetsetsthe clockingof the device.Osc_Mainconfiguresthe oscillatorsource.
XTAL_16MHZ usesa 16 MHZ crystal clock. USE_PLL is a phase lockedloopat400MHZ. SYSDIV_5 divides
the clock bythe numberspecifiedgivingcontrol of the frequency
sys_clock = SysCtlClockGet();
Thisline retrievesthe processorclockrate andassignsit toa variable.
init_LEDs();
InitializesLEDconfigurationandenables by calling the function definition.
init_timer();
InitializesTimerconfigurationandenables by calling the function definition.
IntMasterEnable();
ThisNVICAPIfunctionenablesinterruptsfromthe microprocessortointerruptcontroller.
TimerEnable(TIMER0_BASE, TIMER_A);
ThisTIMER API functionenablesoperationof the timer module.
while(1) {
The while loopprovidesacontinuousloopwhensetto"1".
void init_LEDs(void)
User-definedfunctiondefinitionforinitializingLEDs.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
The SystemControl APIfunctionenablesthe GPIOportF peripheral.
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
The GPIO APIfunctionconfigurespins1,2, or 3 of port F for use as GPIOoutputs.
void init_timer(void)
User-definedfunctiondefinitionforinitializingTIMER0.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
The SystemControl APIfunctionenablesTIMER0 peripheral.

5. TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC);
The TimerAPI functionconfiguresthe timerasa 32-bitfull-widthperiodictimer.
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerAPI functionspecifiesthe base addressforconfiguration,the correctname fora full-width
timer,andthe load value specifiedbyuser-definedconstants.
IntRegister(INT_TIMER0A, Timer0_ISR);
The NVICAPIfunctionregistersthe "TIMER0_ISR"functiontobe calledwhenthe "TIMER0A"interruptis
enabled.
IntEnable(INT_TIMER0A);
The NVICAPIfunctionenables"TIMER0A"asa full-widthtimer tobe usedforthe interruptfunction
process.
TimerIntEnable(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
The TimerAPI functionenablesthe specifictimermodule(TIMER0_Base) forthe timerinterruptsource.
The bit maskof the interruptsource tobe enabledis"TIMER_TIMA_TIMEOUT".
void Timer0_ISR(void)
User-definedfunctiondefinitionforinterrupthandler.The functionreturnsavalue of 0.
TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
The TimerAPI functionclearsthe timerinterruptsources.TIMER0 isthe base specifiedand
"TIMER_TIMA_TIMEOUT" isthe bitmaskfor the interruptsource cleared.
if(GPIOPinRead(GPIO_PORTF_BASE, GPIO_PIN_2)) {
If the GPIOAPIfunctionreadspin 2 fromport F,read line 88.
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0);
The GPIO APIfunctionwritesa0 to pins1,2, or 3 clearingthe blue LED.
else {
Else the GPIO APIfunction...
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 4);
Writesthe value of 4 to pin2 displayingthe blue LED.
Port F interface

6. The GPIO APIfunctionconfiguresportFforoutput.It furtherspecifiesthatpins1,2,and 3, inport F, will
be usedfor output. The launchpadschematicshowsPortFhas 5 pins.Pin1 is the redLED, Pin2 is the
blue LED, and Pin3 is the greenLED. The remainingpins(0and 4) are forthe USR SV.Afterthe GPIO
functionconfiguresthe pinsasoutput,itcanwrite valuesof 2, 3, and 4 for red,green,andblue,
respectively.The programactuallywritesa"4"to the pin2 whichoperatesthe blue LED.
Calculated TIMER0_FREQ
Timer0_Freq 1 2 5 10
Calculated 1Hz 2Hz 5Hz 10Hz
#define TIMER0_FREQ 1
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
sys_clock = SysCtlClockGet();
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerLoadSetfunction hasaparameterfor the "loadvalue".The loadvalue is
"sys_clock/TIMER0_FREQ -1". Thissetsthe periodforthe timer.The sys_clockvariable issettothe
value of the systemclock.The systemclockisconfiguredfor40 MHz. The TIMER0_FREQ variable isset
to 1. Therefore,
40,000,000/1 = 1 period
1/period= frequency
1/40,000,000 = 0.000000025 = frequencyof timer
The timeris enabledalongwiththe runningsystemclock.The frequenciesof boththe timerandsystem
clock mustbe takenintoaccount for the overall frequency of the interruptcausedbyenablingthe timer.
Therefore,
frequencyof timer*frequencyof systemclock= frequencyof timerinterrupt
0.000000025 * 40,000,000 = 1 Hz
#define TIMER0_FREQ 2
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
sys_clock = SysCtlClockGet();
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerLoadSetfunctionhasaparameterfor the "loadvalue".The loadvalue is
"sys_clock/TIMER0_FREQ -1". Thissetsthe periodforthe timer.The sys_clockvariable issettothe
value of the systemclock.The systemclockisconfiguredfor40 MHz. The TIMER0_FREQ variable isset
to 2. Therefore,
40,000,000/2 = 1 period
1/period= frequency
1/20,000,000 = 0.00000005 = frequencyof timer

7. The timeris enabledalongwiththe runningsystemclock.The frequenciesof boththe timerandsystem
clock mustbe takenintoaccount for the overall frequencyof the interruptcausedbyenablingthe timer.
Therefore,
frequencyof timer*frequencyof systemclock= frequencyof timerinterrupt
0.00000005 * 40,000,000 = 2 Hz
#define TIMER0_FREQ 5
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
sys_clock = SysCtlClockGet();
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerLoadSetfunctionhasaparameterfor the "loadvalue".The loadvalue is
"sys_clock/TIMER0_FREQ -1". Thissetsthe periodforthe timer.The sys_clockvariable issettothe
value of the systemclock.The systemclockisconfiguredfor40 MHz. The TIMER0_FREQ variable isset
to 5. Therefore,
40,000,000/5 = 1 period
1/period= frequency
1/8,000,000 = 0.000000125 = frequencyof timer
The timeris enabledalongwiththe runningsystem clock.The frequenciesof boththe timerandsystem
clock mustbe takenintoaccount for the overall frequencyof the interruptcausedbyenablingthe timer.
Therefore,
frequencyof timer*frequencyof systemclock= frequencyof timerinterrupt
0.000000125 * 40,000,000 = 5 Hz
#define TIMER0_FREQ 10
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
sys_clock = SysCtlClockGet();
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerLoadSetfunction hasaparameterfor the "loadvalue".The loadvalue is
"sys_clock/TIMER0_FREQ -1". Thissetsthe periodforthe timer.The sys_clockvariable issettothe
value of the systemclock.The systemclockisconfiguredfor40 MHz. The TIMER0_FREQ variable isset
to 10. Therefore,
40,000,000/10 = 1 period
1/period= frequency
1/4,000,000 = 0.00000025 = frequencyof timer
The timeris enabledalongwiththe runningsystemclock.The frequenciesof boththe timerandsystem
clock mustbe takenintoaccount for the overall frequencyof the interruptcausedbyenablingthe timer.
Therefore,
frequencyof timer*frequencyof systemclock= frequencyof timerinterrupt
0.00000025 * 40,000,000 = 10 Hz

8. Captured Oscilloscope Signal Waveform
Figure 1 10 Hz

9. Figure 2 5 Hz
Figure 3 2 Hz

10. Figure 4 1 Hz
Problem 2
/*************************************************
Blink LEDs on Tiva C Series LaunchPad
with SysTick timer.
By Dr. Xinrong Li, xinrong@UNT.EDU, Aug. 25, 2014
Adapted from Tiva example code.
*************************************************/
Commentsaboutthe programusuallybythe programmer.
#include <stdint.h>
Thisline containsthe headerfile forvariabledefinitions.The headerfileisalreadydefinedinthe CCS
software.The file isconsideredpartof the currentprogram when"#include"isstatedbeforethe name
of the headerfile.Examplesof the valuesare bitsize,precision, andsignedorunsignedintegers.
#include <stdbool.h>

11. Thisline containsthe headerfile forBooleandefinitions.The headerfile isalreadydefinedinthe CCS
software.The file isconsideredpartof the currentprogram when"#include"isstatedbeforethe name
of the headerfile.The file definitionsare usedforoperations,comparingvariables,andprogramcontrol
flow.
#include "inc/tm4c123gh6pm.h"
Thisline containsthe headerfile forthe TM4C123GH6PM microcontroller.The headerfile ispart-
specificandcontainsmacrosand definitionstosimplifyprogrammingthe peripheral'sregistersand
interruptcontrol.Thisiscontainedinthe incdirectory. The file isconsideredpartof the currentprogram
when"#include"isstatedbefore the name of the headerfile.The .cfile forthe TM4C123GH6PM
microcontrollerisincludedinthe projectfolderfordirectaccess.
#include "inc/hw_memmap.h"
Thisline containsthe headerfile forthe TivaCSeriesdevice memorymapdefinitions.The headerfile
containsmanyof the same definitionsusedfordirectregisteraccess.The headerfilecontainsmacros
and definitionstosimplifyprogrammingthe peripheral'sregistersandinterruptcontrol.Thisis
containedinthe incdirectory.The file isconsideredpartof the current programwhen"#include"is
statedbefore the name of the headerfile.The definitionsare usedbydriverlibrariesandare hidden
fromthe programmer.
#include "inc/hw_types.h"
Thisline containsthe headerfile forcommontypesandmacros.The headerfile containsmanyof the
same definitionsusedfordirectregisteraccess.Thisiscontainedinthe incdirectory.The file is
consideredpartof the currentprogram when"#include"isstatedbefore the name of the headerfile.
The definitionsare usedbydriverlibrariesandare hiddenfromthe programmer.The valuesare a wide
varietyof general use foritemssuchas arithmetic,clocktiming,file recognition,anddevice recognition.
#include "driverlib/sysctl.h"
Thisline containsthe headerfile forthe SystemControl APIdefinitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The file isconsideredpartof the currentprogram when
"#include"isstatedbefore the name of the headerfile.The driversprovide guidedcontrol of the
peripheralsandallowsforquickapplication.Enablingperipheralsisanexample of thiscontrol.
#include "driverlib/interrupt.h"
Thisline containsthe headerfile forthe SystemControl APIdefinitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The file isconsideredpartof the currentprogram when
"#include"isstatedbefore the name of the headerfile.The driversprovide guidedcontrol of the
peripheralsandallowsforquickapplication.Enablingperipheralsisanexample of thiscontrol.
#include "driverlib/gpio.h"

12. Thisline containsthe headerfile forGPIOAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The fileisconsideredpartof the currentprogram when"#include"is
statedbefore the name of the headerfile.The driverprovidesasetof functionstocontrol the inputand
outputmodule.
#include "driverlib/systick.h"
Thisline containsthe headerfile forTimerAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The fileisconsideredpartof the currentprogram when"#include"is
statedbefore the name of the headerfile.The driversprovide quickcontrol of the peripheralsand
allowsforquickapplication.The timerAPIprovidesasetof functionsforusingthe timermodule.
#define TIMER0_FREQ 10
Createsa constantusedfor frequencyinthe TimerAPImacrowitha value of 10 Hz.
void init_LEDs(void);
Thisline declaresthe functionprototype "init_LEDs".Declarationatthispointgivesthe actual functiona
global scope.Anyotherfunction,header,or.c file containedinthissource file isgivenaccesstothe
functionandaccessible bythe function.
void init_timer(void);
Thisline declaresthe functionprototype " init_timer".Declarationatthispointgivesthe actual function
a global scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccesstothe
functionandaccessible bythe function.
void Timer0_ISR(void);
Thisline declaresthe functionprototype " Timer0_ISR".Declarationat thispointgivesthe actual
functionaglobal scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccess
to the functionandaccessible bythe function.
uint32_t sys_clock;
Createsan unsigned32-bitglobal variable forthe systemclock.
int main(void){
The main processcallsandacts on variables,macros,definitions,andothersystemfunctions.
SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
SystemControl ClockSetsetsthe clockingof the device.Osc_Mainconfiguresthe oscillatorsource.
XTAL_16MHZ usesa 16 MHZ crystal clock. USE_PLL is a phase lockedloopat400MHZ. SYSDIV_2_5
dividesthe clockbythe numberspecifiedgivingcontrol of the frequency.
sys_clock = 80000000;

13. Thisline retrievesthe processorclockrate andassignsit toa variable.
init_LEDs();
InitializesLEDconfigurationandenables by calling the function definition.
init_SysTick();
InitializesSysTick configurationandenables by calling the function definition.
IntMasterEnable();
ThisNVICAPIfunctionenables interruptsfromthe microprocessortointerruptcontroller.
SysTickEnable();
ThisSysTickAPI functionenablesoperationof the timer module.
while(1) {
The while loopprovidesacontinuousloopwhensetto"1".
void init_LEDs(void)
User-definedfunction definitionforinitializingLEDs.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
The SystemControl APIfunctionenablesthe GPIOportF peripheral.
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
The GPIO APIfunctionconfigurespins1,2, and3 of portF for use as GPIO outputs.
void init_SysTick(void)
User-definedfunctiondefinitionforinitializingSysTick.The functionreturnsavalue of 0.
SysTickPeriodSet(sys_clock/TIMER0_FREQ);
The SysTick APIfunctionconfigures the value specifiedbyuser-definedconstants.
SysTickIntRegister(SysTick_ISR);
The NVICAPIfunctionregistersthe "SysTick_ISR"functiontobe calledwhenthe "SysTick"interruptis
enabled.
SysTickIntEnable();
The SysTickAPIfunctionenablesthe specificSysTickmodule(TIMER0_Base) forthe SysTickinterrupt
source.

14. void SysTick_ISR(void)
User-definedfunctiondefinitionforinitializingSysTick_ISR.The functionreturnsavalue of 0.
if(GPIOPinRead(GPIO_PORTF_BASE, GPIO_PIN_3)) {
If the GPIOAPIfunctionreadspin 3 fromport F,read line 80.
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0);
The GPIO APIfunctionwritesa0 to pins1,2, or 3 clearingthe greenLED.
else {
Else the GPIO APIfunction ...
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_3, 8);
Writesthe value of 8 to pin3 turningonthe greenLED.
Calculated Timer0_Freq
Timer0_Freq 10 8 5 2 1
Signal Freq 10Hz 8 Hz 5 Hz 13.33 Hz 6.45 Hz
I was unable togetthe correct frequencywhenIwentto 2 Hz. The smallestfrequencythatIcan
generate correctlywiththe SysTicktimeris5 Hz.
Problem 3
/*************************************************
Interaction through UART, and
print debug messages on UART terminal.
By Dr. Xinrong Li, xinrong@UNT.EDU, Aug. 28, 2014
Adapted from Tiva example code.
*************************************************/
Commentsaboutthe programusuallybythe programmer.
#include <stdint.h>
Thisline containsthe headerfile forvariabledefinitions.The headerfile isalreadydefinedinthe CCS
software.The file isconsideredpartof the currentprogram when"#include"isstatedbeforethe name
of the headerfile.Examplesof the valuesare bitsize,precision,andsignedorunsignedintegers.
#include <stdbool.h>
Thisline containsthe headerfile forBooleandefinitions.The headerfile isalreadydefinedinthe CCS
software.The file isconsideredpartof the currentprogram when"#include"isstatedbeforethe name

15. of the headerfile.The file definitionsare usedforoperations,comparingvariables,andprogramcontrol
flow.
#include "inc/tm4c123gh6pm.h"
Thisline containsthe headerfile forthe TM4C123GH6PM microcontroller.The headerfile ispart-
specificandcontainsmacrosand definitionstosimplifyprogrammingthe peripheral'sregistersand
interruptcontrol.Thisiscontainedinthe incdirectory.The file isconsideredpartof the currentprogram
when"#include"isstatedbefore the name of the headerfile.The .cfile forthe TM4C123GH6PM
microcontrollerisincludedinthe projectfolderfordirectaccess.
#include "inc/hw_memmap.h"
Thisline containsthe headerfile forthe TivaCSeriesdevice memorymapdefinitions.The headerfile
containsmanyof the same definitionsusedfordirectregisteraccess.The headerfilecontainsmacros
and definitionstosimplifyprogrammingthe peripheral'sregistersandinterruptcontrol.Thisis
containedinthe incdirectory.The file isconsideredpartof the current programwhen"#include"is
statedbefore the name of the headerfile.The definitionsare usedbydriverlibrariesandare hidden
fromthe programmer.
#include "inc/hw_types.h"
Thisline containsthe headerfile forcommontypesandmacros.The headerfile containsmanyof the
same definitionsusedfordirectregisteraccess.Thisiscontainedinthe incdirectory.The file is
consideredpartof the currentprogram when"#include"isstatedbefore the name of the headerfile.
The definitionsare usedbydriverlibrariesandare hiddenfromthe programmer.The valuesare a wide
varietyof general use foritemssuchas arithmetic,clocktiming,file recognition,anddevice recognition.
#include "driverlib/sysctl.h"
Thisline containsthe headerfile forthe SystemControl APIdefinitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The file isconsideredpartof the currentprogram when
"#include"isstatedbefore the name of the headerfile.The driversprovide guidedcontrol of the
peripheralsandallowsforquickapplication.Enablingperipheralsisanexample of thiscontrol.
#include "driverlib/interrupt.h"
Thisline containsthe headerfile forthe SystemControl APIdefinitionsandmacros.The headerfile isin
the directory"driverlib"of the CCSsoftware.The file isconsideredpartof the currentprogram when
"#include"isstatedbefore the name of the headerfile.The driversprovide guidedcontrol of the
peripheralsandallowsforquickapplication.Enablingperipheralsisanexample of thiscontrol.
#include "driverlib/gpio.h"
Thisline containsthe headerfile forGPIOAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The fileisconsideredpartof the currentprogram when"#include"is

16. statedbefore the name of the headerfile.The driverprovidesasetof functionstocontrol the inputand
outputmodule.
#include "driverlib/timer.h"
Thisline containsthe headerfile forTimerAPIdefinitionsandmacros.The headerfile isinthe directory
"driverlib"of the CCSsoftware.The fileisconsideredpartof the currentprogram when"#include"is
statedbefore the name of the headerfile.The driversprovide quickcontrol of the peripheralsand
allowsforquickapplication.The timerAPIprovidesasetof functionsforusingthe timermodule.
#include "driverlib/pin_map.h"
Thisline containsthe headerfile forpin_mapAPIdefinitionsandmacros.The headerfile isinthe
directory"driverlib"of the CCSsoftware.The file isconsideredpartof the current programwhen
"#include"isstatedbefore the name of the headerfile.The driversprovide quickcontrol of the
peripheralsandallowsforquickapplication.The pin_map APIprovidesamapof the peripheral topin
configuration.
#include "driverlib/uart.h"
Thisline containsthe headerfile forUART(Universal AsynchronousReceiver/Transmitter) API
definitionsandmacros.The headerfile isinthe directory"driverlib"of the CCSsoftware.The file is
consideredpartof the currentprogram when"#include"isstatedbefore the name of the headerfile.
The driversprovide quickcontrol of the peripheralsandallowsforquickapplication.The UARTAPI
providesasetof functionsforusingthe TIVA UART module.
#include "utils/uartstdio.h"
Thisline containsthe header file forUART.The header file isinthe directory"utils"of the CCS
software.The file isconsideredpartof the currentprogram when"#include"isstatedbeforethe name
of the headerfile.The utilityprovidesquickcontrol of the peripheralsand allowsforquickapplication.
The file containsprototypesforthe UARTconsole functions.Onbuildingthe project,the .cfile hadtobe
addedmanuallytolinkthe filestogether.
#define TIMER0_FREQ 2
Createsa constantusedfor frequencyinthe TimerAPImacrowitha value of 2 Hz.
#define UART0_BAUDRATE 115200
Createsa constantusedfor baudrate inthe UART APImacro witha of value 115200 bps.
#define RED_LED GPIO_PIN_1
Createsa constantfor pin1 inthe GPIO APImodule thatdisplaysthe redLED.
#define BLUE_LED GPIO_PIN_2

17. Createsa constantfor pin2 inthe GPIO APImodule thatdisplaysthe blue LED.
#define GREEN_LED GPIO_PIN_3
Createsa constantfor pin3 inthe GPIO APImodule thatdisplaysthe greenLED.
#define NUM_DISP_TEXT_LINE 4
Createsa constantfor the numberof linesof textdisplayinthe characterpointer"disp_text"witha
value of 4.
void init_LEDs(void);
Thisline declaresthe functionprototype "init_LEDs".Declarationatthispointgivesthe actual functiona
global scope.Anyotherfunction,header,or.c file containedinthissource file isgivenaccesstothe
functionandaccessible bythe function.
void init_timer(void);
Thisline declaresthe functionprototype " init_timer".Declarationatthispoint givesthe actual function
a global scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccesstothe
functionandaccessible bythe function.
void init_UART(void);
Thisline declaresthe functionprototype " init_UART". Declarationatthispointgivesthe actual function
a global scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccesstothe
functionandaccessible bythe function.
void Timer0_ISR(void);
Thisline declaresthe function prototype "Timer0_ISR".Declarationat thispointgivesthe actual
functionaglobal scope.Anyotherfunction,header,or.cfile containedinthissource fileisgivenaccess
to the functionandaccessible bythe function.
extern void UARTStdioIntHandler(void);
Thisline declaresafunctionprototype of type "extern".Thisinformsthe microprocessorthatitneedsto
access a functionthatexistsoutsideof thissource file.The uartstdio.cfileisincludedinthe project
folderfordirectaccess.The uartstdio.cfile hasadditional functionsforthe UARTconsole.Thisparticular
functionhandlesinterruptsfromthe UART.The UART has a transmitandreceive bufferthatisusedfor
data transfersbetweenthe microprocessorandthe puttyconsole.
uint32_t sys_clock;
Createsan unsigned32-bitglobal variable forthe systemclock.
uint8_t cur_LED = RED_LED;

18. Createsan unsigned32-bitglobal variable forthe systemclock.
const char *disp_text[NUM_DISP_TEXT_LINE] = {
"n",
"UART and LED Demon",
"H: help, R: red, G: green, B: blue.n",
"> " };
Thisline createsa pointer fora systemmessage communicatedtothe userviaputtyconsole..
int main(void){
The main processcallsandacts on variables,macros,definitions,andothersystem functions.
uint32_t i;
Createsan unsigned32-bitvariable forloops.
unsigned char user_cmd;
Createsan unsignedcharactervariable foruserinput.
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
SystemControl Clock Setsetsthe clockingof the device.Osc_Mainconfiguresthe oscillatorsource.
XTAL_16MHZ usesa 16 MHZ crystal clock. USE_PLL is a phase lockedloopat400MHZ. SYSDIV_5 divides
the clock bythe numberspecifiedgivingcontrol of the frequency.
sys_clock = SysCtlClockGet();
Thisline retrievesthe processorclockrate andassignsit toa variable.
init_LEDs();
InitializesLEDconfigurationandenables by calling the function definition.
init_UART();
InitializesUARTconfigurationandenables by calling the function definition.
init_timer();
InitializesTimerconfigurationandenables by calling the function definition.
IntMasterEnable();
ThisNVICAPIfunctionenablesinterruptsfromthe microprocessortointerruptcontroller.
TimerEnable(TIMER0_BASE, TIMER_A);
ThisTIMER API functionenablesoperationof the timer module.

19. for(i=0; i<NUM_DISP_TEXT_LINE; i++)
Thisline isa for loopto displayprogrammessage onconsole.
UARTprintf(disp_text[i]);
Thisfunctionprintsthe message onthe console.
while(1) {
The while loopprovidesacontinuousloopwhensetto"1".
if(UARTRxBytesAvail())
If the UART has available userinput.
user_cmd = UARTgetc();
Thisline retrievesthe userinputandstoresitina variable.
else
user_cmd = 0;
Else,the usercommandvariable issetto 0.
switch(user_cmd){
Switchcase for the userinputdata.
case 'r':
Switchcase for red.
case ' ':
Switchcase for empty.
case 'H':
Switchcase for H.
case 'h':
Switchcase for h.
for(i=0; i<NUM_DISP_TEXT_LINE; i++)
Switchcase displayforlines87-90 is a for looptodisplayconsole message touser viaputty console.
UARTprintf(disp_text[i]);

20. Thisfunctionprintsthe message onthe putty console.
break;
Switchcase break.
case 'R':
Switchcase for redled.
case 'r':
Switchcase for redled.
cur_LED = RED_LED;
Storesthe red ledincurrentledvariable.
UARTprintf("n> ");
Thisfunctionprintsa newline witha> on the console.
break;
Switchcase break.
case 'B':
Switchcase for blue led.
case 'b':
Switchcase for blue led.
cur_LED = BLUE_LED;
Storesthe blue ledincurrentledvariable.
UARTprintf("n> ");
Thisfunctionprintsa newline witha> on the console.
break;
Switchcase break.
case 'G':
Switchcase for green led.
case 'g':

21. Switchcase for greenled.
cur_LED = GREEN_LED;
Storesthe greenledincurrentledvariable.
UARTprintf("n> ");
Thisfunctionprintsa newline witha> on the console.
break;
Switchcase break.
void init_LEDs(void)
User-defined functiondefinitionforinitializingLEDs.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
The SystemControl APIfunctionenablesthe GPIOportF peripheral.
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
The GPIO APIfunctionconfigurespins1,2, and3 of portF for use as GPIO outputs.
void init_timer(void)
User-definedfunctiondefinitionforinitializingTimer.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
The SystemControl APIfunctionenablesthe timer0peripheral.
TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC);
The TimerAPI functionconfiguresthe timerasa 32-bitfull-widthperiodictimer.
TimerLoadSet(TIMER0_BASE, TIMER_A, sys_clock/TIMER0_FREQ -1);
The TimerAPI functionspecifiesthe base addressforconfiguration,the correctname fora full-width
timer,andthe load value specifiedbyuser-definedconstants.
IntRegister(INT_TIMER0A, Timer0_ISR);
The NVICAPIfunctionregistersthe "TIMER0_ISR"functiontobe calledwhenthe "TIMER0A"interruptis
enabled.
IntEnable(INT_TIMER0A);

22. The NVICAPIfunctionenables"TIMER0A"asa full-widthtimer tobe usedforthe interruptfunction
process.
TimerIntEnable(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
The TimerAPI functionenablesthe specifictimermodule(TIMER0_Base) forthe timerinterruptsource.
The bit maskof the interruptsource tobe enabledis"TIMER_TIMA_TIMEOUT".
void init_UART(void)
User-definedfunctiondefinitionforinitializingUART.The functionreturnsavalue of 0.
SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
The SystemControl APIfunctionenablesthe UART0 peripheral.
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
The SystemControl APIfunctionenablesthe GPIOA peripheral.
GPIOPinConfigure(GPIO_PA0_U0RX);
The GPIO APIfunctionconfiguresthe alternate functionof aGPIO pin.GPIOPort A's pinmux is
configuredforthe UART peripheral.Pin0is configuredforthe UARTreceiverbuffer.
GPIOPinConfigure(GPIO_PA1_U0TX);
The GPIO APIfunctionconfiguresthe alternate functionof aGPIO pin.GPIOPort A's pinmux is
configuredforthe UART0 peripheral.Pin1isconfiguredforthe UART transmitterbuffer.
GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
The GPIO APIfunctionconfigurespinsforuse bythe UART peripheral.GPIOPortA will be the peripheral
usedforUART communication.Pins1and2 of port A are available.
IntRegister(INT_UART0, UARTStdioIntHandler);
The NVICAPIfunctionregistersthe "UARTStdioIntHandler"functiontobe calledwhenthe "UART0"
interruptisenabled.
UARTStdioConfig(0, UART0_BAUDRATE, sys_clock);
The UART driverfunctionconfiguresthe UARTforinput/output.UARTPort0 isthe base that will be
used.The user-definedconstant"UART0_BAUDRATE"isthe bitrate forthe UART and the user-defined
constant "sys_clock"isthe frequencyusedforthe source clockof the UART module.
void Timer0_ISR(void)
User-definedfunctiondefinitionforinterrupthandler.The functionreturnsavalue of 0.

23. TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
The TimerAPI functionclearsthe timerinterruptsources.TIMER0 isthe base specifiedand
"TIMER_TIMA_TIMEOUT" isthe bitmaskfor the interruptsource cleared.
if(GPIOPinRead(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3)) {
If the GPIOAPIfunctionreadspins1,2, or 3 fromport F, readline 164.
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0);
The GPIO APIfunctionwritesa0 to pins1,2, or 3.
else {
Else the GPIO APIfunction...
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, cur_LED);
Writesthe value of the variable "cur_LED" to the correct pin.
Problem 4
The NestedVectorInterruptController(NVIC) functionsasaninterrupthandler.Itcansetpriorities in
interruptsandenable ordisable themtoo.A registercanbe dedicatedfortopperformance.The
controllerhasthe abilitytonestprioritiesandchoose betweenstaticcompilesordynamicrun-time
environment.
The TimerAPI hasa setof functionsforcontrolling,modifying,andmanaginginterrupts.Itcanrun
continuouslyorjustone time ceasingatzeroor the load.It is alsoa full-widthtimerat32.768. Half-
widthgivesthe optionof pulse widthmodulationandsynchronization.
The Universal AsynchronousReceiver/Transmitter(UART) APIfunctionsasaninterrupthandler,send
and receive data,andconfigure andcontrol UART modules.Some of the featuresinclude:
programmable baudrate generator,programmable serial interface,line breakgeneration,and
detection.

24. UART standard IOmodule hasunbufferedandbufferedoperationwithgoodinterrupthandling.
Modificationcanbe made if the bufferisfull.The processorcaneliminate instructionsforfull buffersor
clearprior to utilization.
The ARM Cortex-Mprocessorprovidesimpressive performance andlow powerconsumption.Ithas32-
bitarchitecture withsingle-cyclemultiplyinstructionandexcellentinterrupthandling.Unaligneddata
access providesefficientmemoryandfastcode executionincreases sleeptime.Itmaintainshigh
precisionandhas32 dedicated32-bitregisters.Itsupportsmultiple software platformsand some
controllerscome withabuiltinlibraryforquickapplication.
Summary and Conclusions
The Tiva C SeriesTM4C123G microcontrollerhasattainedbetterprecision,durability,power
management,and interruptcontrol. 32-bitarchitecture andunaligneddataaccessdeliversafast
processingenvironment.These improvementssetanew tone formicro processingandcreative
environments.
References
TexasInstruments.(2014). TivaWarePeripheral Driver Library: User'sGuide. Austin,Texas:TI.