How to programming servo control?

hi.  I'm using MDK 4.72 for ARM, and using a tm4c123g 

I want to servo control , but i can.

my code this. I applied this DCMOTOR.(because, i can`t find a servo library)

// DCMotor.c
// Runs on LM4F120 or TM4C123
// Use SysTick interrupts to implement a software PWM to drive
// a DC motor at a given duty cycle. The built-in button SW1
// increases the speed, and SW2 decreases the speed.
// Daniel Valvano, Jonathan Valvano
// August 6, 2013

/* This example accompanies the book
"Embedded Systems: Introduction to ARM Cortex M Microcontrollers",
ISBN: 978-1469998749, Jonathan Valvano, copyright (c) 2013
"Embedded Systems: Real Time Interfacing to ARM Cortex M Microcontrollers",
ISBN: 978-1463590154, Jonathan Valvano, copyright (c) 2013

Copyright 2013 by Jonathan W. Valvano, valvano@mail.utexas.edu
You may use, edit, run or distribute this file
as long as the above copyright notice remains
THIS SOFTWARE IS PROVIDED "AS IS". NO WARRANTIES, WHETHER EXPRESS, IMPLIED
OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
For more information about my classes, my research, and my books, see
users.ece.utexas.edu/.../
*/

// PA5 connected to DC motor interface

#include "PLL.h"

#define GPIO_PORTA_DATA_R (*((volatile unsigned long *)0x400043FC))
#define GPIO_PORTA_DIR_R (*((volatile unsigned long *)0x40004400))
#define GPIO_PORTA_AFSEL_R (*((volatile unsigned long *)0x40004420))
#define GPIO_PORTA_DR8R_R (*((volatile unsigned long *)0x40004508))
#define GPIO_PORTA_DEN_R (*((volatile unsigned long *)0x4000451C))
#define GPIO_PORTA_AMSEL_R (*((volatile unsigned long *)0x40004528))
#define GPIO_PORTA_PCTL_R (*((volatile unsigned long *)0x4000452C))
#define GPIO_PORTF_DATA_R (*((volatile unsigned long *)0x400253FC))
#define GPIO_PORTF_DIR_R (*((volatile unsigned long *)0x40025400))
#define GPIO_PORTF_IS_R (*((volatile unsigned long *)0x40025404))
#define GPIO_PORTF_IBE_R (*((volatile unsigned long *)0x40025408))
#define GPIO_PORTF_IEV_R (*((volatile unsigned long *)0x4002540C))
#define GPIO_PORTF_IM_R (*((volatile unsigned long *)0x40025410))
#define GPIO_PORTF_RIS_R (*((volatile unsigned long *)0x40025414))
#define GPIO_PORTF_ICR_R (*((volatile unsigned long *)0x4002541C))
#define GPIO_PORTF_AFSEL_R (*((volatile unsigned long *)0x40025420))
#define GPIO_PORTF_PUR_R (*((volatile unsigned long *)0x40025510))
#define GPIO_PORTF_DEN_R (*((volatile unsigned long *)0x4002551C))
#define GPIO_PORTF_LOCK_R (*((volatile unsigned long *)0x40025520))
#define GPIO_LOCK_KEY 0x4C4F434B // Unlocks the GPIO_CR register
#define GPIO_PORTF_CR_R (*((volatile unsigned long *)0x40025524))
#define GPIO_PORTF_AMSEL_R (*((volatile unsigned long *)0x40025528))
#define GPIO_PORTF_PCTL_R (*((volatile unsigned long *)0x4002552C))
#define SYSCTL_RCGC2_R (*((volatile unsigned long *)0x400FE108))
#define NVIC_ST_CTRL_R (*((volatile unsigned long *)0xE000E010))
#define NVIC_ST_RELOAD_R (*((volatile unsigned long *)0xE000E014))
#define NVIC_ST_CURRENT_R (*((volatile unsigned long *)0xE000E018))
#define NVIC_EN0_R (*((volatile unsigned long *)0xE000E100))
#define NVIC_PRI7_R (*((volatile unsigned long *)0xE000E41C))
#define NVIC_SYS_PRI3_R (*((volatile unsigned long *)0xE000ED20))

// basic functions defined at end of startup.s
void DisableInterrupts(void); // Disable interrupts
void EnableInterrupts(void); // Enable interrupts
long StartCritical (void); // previous I bit, disable interrupts
void EndCritical(long sr); // restore I bit to previous value
void WaitForInterrupt(void); // low power mode

unsigned long H,L;
unsigned long degree;
void Motor_Init(void){
SYSCTL_RCGC2_R |= 0x00000001; // activate clock for port A
H = L = 0; // 0% start not active
degree = 0;
GPIO_PORTA_AMSEL_R &= ~0x20; // disable analog functionality on PA5
GPIO_PORTA_PCTL_R &= ~0x00F00000; // configure PA5 as GPIO
GPIO_PORTA_DIR_R |= 0x20; // make PA5 out
GPIO_PORTA_DR8R_R |= 0x20; // enable 8 mA drive on PA5
GPIO_PORTA_AFSEL_R &= ~0x20; // disable alt funct on PA5
GPIO_PORTA_DEN_R |= 0x20; // enable digital I/O on PA5
GPIO_PORTA_DATA_R &= ~0x20; // make PA5 low
NVIC_ST_CTRL_R = 0; // disable SysTick during setup
NVIC_ST_RELOAD_R = L-1; // reload value for 500us
NVIC_ST_CURRENT_R = 0; // any write to current clears it
NVIC_SYS_PRI3_R = (NVIC_SYS_PRI3_R&0x00FFFFFF)|0x40000000; // priority 2
NVIC_ST_CTRL_R = 0x00000007; // enable with core clock and interrupts
}
void SysTick_Handler(void){
if(GPIO_PORTA_DATA_R&0x20){ // toggle PA5
GPIO_PORTA_DATA_R &= ~0x20; // make PA5 low
NVIC_ST_RELOAD_R = L-1; // reload value for low phase
} else{
GPIO_PORTA_DATA_R |= 0x20; // make PA5 high
NVIC_ST_RELOAD_R = H-1; // reload value for high phase
}
}
void Switch_Init(void){ unsigned long volatile delay;
SYSCTL_RCGC2_R |= 0x00000020; // (a) activate clock for port F
delay = SYSCTL_RCGC2_R;
GPIO_PORTF_LOCK_R = 0x4C4F434B; // unlock GPIO Port F
GPIO_PORTF_CR_R = 0x11; // allow changes to PF4,0
GPIO_PORTF_DIR_R &= ~0x11; // (c) make PF4,0 in (built-in button)
GPIO_PORTF_AFSEL_R &= ~0x11; // disable alt funct on PF4,0
GPIO_PORTF_DEN_R |= 0x11; // enable digital I/O on PF4,0
GPIO_PORTF_PCTL_R &= ~0x000F000F; // configure PF4,0 as GPIO
GPIO_PORTF_AMSEL_R &= ~0x11; // disable analog functionality on PF4,0
GPIO_PORTF_PUR_R |= 0x11; // enable weak pull-up on PF4,0
GPIO_PORTF_IS_R &= ~0x11; // (d) PF4,PF0 is edge-sensitive
GPIO_PORTF_IBE_R &= ~0x11; // PF4,PF0 is not both edges
GPIO_PORTF_IEV_R &= ~0x11; // PF4,PF0 falling edge event
GPIO_PORTF_ICR_R = 0x11; // (e) clear flags 4,0
GPIO_PORTF_IM_R |= 0x11; // (f) arm interrupt on PF4,PF0
NVIC_PRI7_R = (NVIC_PRI7_R&0xFF00FFFF)|0x00400000; // (g) priority 2
NVIC_EN0_R = 0x40000000; // (h) enable interrupt 30 in NVIC
}
// L range: 8000,16000,24000,32000,40000,48000,56000,64000,72000
// power: 10% 20% 30% 40% 50% 60% 70% 80% 90%
void GPIOPortF_Handler(void){ // called on touch of either SW1 or SW2
if(GPIO_PORTF_RIS_R&0x01){ // SW2 touch
GPIO_PORTF_ICR_R = 0x01; // acknowledge flag0
degree += 40;
if(L>0) L = 0; // slow down
}
if(GPIO_PORTF_RIS_R&0x10){ // SW1 touch
GPIO_PORTF_ICR_R = 0x10; // acknowledge flag4
degree += 40;
if(L<72000) L = L+16000; // speed up
}
// H = 80000-L; // constant period of 1ms, variable duty cycle
}

int main(void){
DisableInterrupts(); // disable interrupts while initializing
PLL_Init(); // bus clock at 80 MHz
Motor_Init(); // output from PA5, SysTick interrupts
Switch_Init(); // arm PF4, PF0 for falling edge interrupts
EnableInterrupts(); // enable after all initialization are done
while(1){
// main program is free to perform other tasks
WaitForInterrupt(); // low power mode
}
}

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