有没有大神帮我看一下这个程序，我是小白 看不太懂

这是主函数，TIM后面的数字表示什么？
#include "include.h"
#include "DZXH_STM32_UltrasonicWave1.h"
#include "dzxh_stm32_gpio.h"
#include "dzxh_stm32_delay.h"
#include "dzxh_stm32_pwm.h"
void init()
{
delay_init();
UltrasonicWave_Configuration();
NVIC_HC_Configuration();
Timerx_HC_Init(5000,7199);
delay_HC_init(72);
GPIO_Common_Init(2,GPIO_Pin_12|GPIO_Pin_13,GPIO_Mode_Out_PP);
TIM_PWM_Init(2,72,20000,1100,1,0);
TIM_PWM_Init(2,72,20000,1100,2,0);
TIM_PWM_Init(2,72,20000,1100,3,0);
TIM_PWM_Init(2,72,20000,1100,4,0);
}
int main(void)
{
init();
while(1)
{
UltrasonicWave_StartMeasure();
Change_PWM_pulse(TIM2,1,5);
Change_PWM_pulse(TIM2,2,6000);
Change_PWM_pulse(TIM2,3,5);
Change_PWM_pulse(TIM2,4,6000);
if(UltrasonicWave_Distance<=20)
{
Change_PWM_pulse(TIM2,2,5);
Change_PWM_pulse(TIM2,1,6000);
Change_PWM_pulse(TIM2,4,5);
Change_PWM_pulse(TIM2,3,6000);
delay_ms(1000);
Change_PWM_pulse(TIM2,2,6000);
Change_PWM_pulse(TIM2,1,6000);
Change_PWM_pulse(TIM2,3,5);
Change_PWM_pulse(TIM2,4,6000);
delay_ms(1000);
}
}
}
这是超声波测距功能函数
#include "DZXH_STM32_UltrasonicWave1.h"
#include "misc.h"
#define TRIG_PORT GPIOB //TRIG
#define ECHO_PORT GPIOB //ECHO
#define TRIG_PIN GPIO_Pin_8 //TRIG
#define ECHO_PIN GPIO_Pin_7 //ECHO
float UltrasonicWave_Distance;
void NVIC_HC_Configuration(void)
{
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
}
void UltrasonicWave_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
EXTI_InitTypeDef EXTI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable , ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB|RCC_APB2Periph_AFIO, ENABLE);
GPIO_InitStructure.GPIO_Pin = TRIG_PIN; //PC8½ÓTRIG
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(TRIG_PORT, &GPIO_Ini