PWM output experiment based on stm32f103zet6 library function

send use TIM3 The passage of 2, Put the channel 2 Remap to PB5, produce PWM To control DS0 The brightness of .

PWM brief introduction

A little bit more simple , It's the control of pulse width .

STM32 In addition to TIM6 and 7. Other timers can be used to generate PWM Output . Among them, high-level setting Chronometer TIM1 and TIM8 It can produce as many as 7 On the road PWM Output . And universal timers can also generate up to 4 On the road PWM Output , such ,STM32 At most... Can be generated at the same time 30 road PWM Output ！ Here we only use TIM3 Of CH2 All the way to PWM Output . If you want to generate multiple outputs , You can make some modifications according to our code .

Configure this through library functions Functional steps . PWM The related functions are set in the library function file stm32f10x_tim.h and stm32f10x_tim.c In file .
1. Turn on TIM3 Clock and multiplexing function clock , To configure PB5 For multiplex output .
To use TIM3, We have to turn on TIM3 The clock of . Here we have to configure PB5 For multiplex output , This is because TIM3_CH2 The channel will be remapped to PB5 On , here ,PB5 It belongs to multiplexing function output . Library functions enable TIM3 The way to clock is ：

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); // Enable timer  3  The clock  

Library function settings AFIO The way to clock is ：

RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);  // Multiplex clock enable  

Here is a brief list of GPIO Just initialize one line of code ：

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  // Multiplexing push pull output  

2. Set up TIM3_CH2 Remap to PB5 On .
because TIM3_CH2 The default is connected to PA7 Upper , So we need to set TIM3_REMAP For partial remapping （ through too AFIO_MAPR To configure ）, Give Way TIM3_CH2 Remap to PB5 above . Set the remapping function in the library function The number is ：

void GPIO_PinRemapConfig(uint32_t GPIO_Remap, FunctionalState NewState); 

STM32 Remapping can only remap to a specific port . first The entry parameter can be understood as setting the type of remapping , such as TIM3 Some remapping entry parameters are GPIO_PartialRemap_TIM3, this Dot can be just as the name suggests . therefore TIM3 The library function implementation method of partial remapping is ：

GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); 

3. initialization TIM3, Set up TIM3 Of ARR and PSC.
In the open TIM3 After the clock , We need to set ARR and PSC Two registers to control the output PWM Of cycle . When PWM The cycle is too slow （ lower than 50Hz） When , We'll obviously feel the flicker . therefore ,PWM Zhou The period should not be set too small here . This is in the library function by TIM_TimeBaseInit Functionally implemented

TIM_TimeBaseStructure.TIM_Period = arr; 										// Set auto reload load value  
TIM_TimeBaseStructure.TIM_Prescaler =psc; 										// Set the prescaler value  
TIM_TimeBaseStructure.TIM_ClockDivision = 0; 									// Set the clock split :TDTS = Tck_tim 
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 					// Upcount mode  
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); 								// Initialize... According to the specified parameters  TIMx  Of  

4. Set up TIM3_CH2 Of PWM Pattern , Can make TIM3 Of CH2 Output .
We need to set TIM3_CH2 by PWM Pattern （ The default is frozen ）, Because of our DS0 It's low power Ping Liang , And we want to be CCR2 When the value is small ,DS0 It's dark ,CCR2 When it's high ,DS0 Just light up , So I We need to configure TIM3_CCMR1 To control TIM3_CH2 The pattern of . In library functions ,PWM Channel setting Setting is through the function TIM_OC1Init()~TIM_OC4Init() To set up , Different channels have different settings , Here I am They use channels 2, So the function used is TIM_OC2Init().

void TIM_OC2Init(TIM_TypeDef* TIMx, TIM_OCInitTypeDef* TIM_OCInitStruct); 

Look at the structure TIM_OCInitTypeDef The definition of ：

typedef struct 
{
       
	uint16_t TIM_OCMode; 
	uint16_t TIM_OutputState;     
	uint16_t TIM_OutputNState;    
	uint16_t TIM_Pulse;            
	uint16_t TIM_OCPolarity;       
	uint16_t TIM_OCNPolarity;      
	uint16_t TIM_OCIdleState;     
	uint16_t TIM_OCNIdleState;   
}TIM_OCInitTypeDef; 

Here we will explain several member variables related to our requirements ：
Parameters TIM_OCMode The setting mode is PWM Or output comparison , Here we are PWM Pattern .
Parameters TIM_OutputState Used to set the compare output enable , That is to enable PWM Output to port .
Parameters TIM_OCPolarity Used to set whether the polarity is high or low .
Other parameters TIM_OutputNState,TIM_OCNPolarity,TIM_OCIdleState and TIM_OCNIdleState yes Advanced timer TIM1 and TIM8 Just used .

To implement the scenario we mentioned above , The method is ：

TIM_OCInitTypeDef  TIM_OCInitStructure;  
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; 						// choice  PWM  Pattern  2 
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 			// Compare output enable  
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 				// High output polarity  
TIM_OC2Init(TIM3, &TIM_OCInitStructure);  								// initialization  TIM3 OC2 

5. Can make TIM3.
After completing the above settings , We need to enable TIM3.

TIM_Cmd(TIM3, ENABLE);  // Can make  TIM3 

6. modify TIM3_CCR2 To control the duty cycle .
After the above settings ,PWM In fact, it has started to output , But its duty cycle and frequency are fixed Of , And we modify it TIM3_CCR2 You can control CH2 The output duty cycle of . And then control DS0 The brightness of .
In library functions , modify TIM3_CCR2 The function of the duty cycle is ：

void TIM_SetCompare2(TIM_TypeDef* TIMx, uint16_t Compare2); 

For other channels , There is a function name , The function format is TIM_SetComparex(x=1,2,3,4).
Through the above 6 A step , We can control TIM3 Of CH2 Output PWM Wave .

Hardware design

The hardware resources used in this experiment are ：
1） Indicator light DS0
2） Timer TIM3

software design

stay timer.c It's added to it The following code ：

//TIM3 PWM Partial initialization  
//PWM Output initialization 
//arr： Auto reload value 
//psc： Clock presplitting frequency 
void TIM3_PWM_Init(u16 arr,u16 psc)
{
      
	GPIO_InitTypeDef GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef  TIM_OCInitStructure;
	
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);							// Enable timer 3 The clock 
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB  | RCC_APB2Periph_AFIO, ENABLE);    // Can make GPIO Peripherals and AFIO Multiplexing function module clock 
	
	GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); 							//Timer3 Partial remapping  TIM3_CH2->PB5 
	
	// Set this pin to multiplex output function , Output TIM3 CH2 Of PWM Pulse shape  GPIOB.5
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; 										//TIM_CH2
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  								// Multiplexing push pull output 
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOB, &GPIO_InitStructure);											// initialization GPIO
	
	// initialization TIM3
	TIM_TimeBaseStructure.TIM_Period = arr; 										// Set the value of the auto reload register cycle for the next update event load activity 
	TIM_TimeBaseStructure.TIM_Prescaler =psc; 										// Set as TIMx Prescaled value of clock frequency divisor  
	TIM_TimeBaseStructure.TIM_ClockDivision = 0; 									// Set the clock split :TDTS = Tck_tim
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  					//TIM Upcount mode 
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); 								// according to TIM_TimeBaseInitStruct The parameter specified in TIMx Unit of time base 
	
	// initialization TIM3 Channel2 PWM Pattern  
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; 								// Select timer mode :TIM Pulse width modulation mode 2
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 					// Compare output enable 
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 						// Output polarity :TIM High output polarity 
	TIM_OC2Init(TIM3, &TIM_OCInitStructure);  										// according to T The specified parameter initializes the peripheral TIM3 OC2
	
	TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  								// Can make TIM3 stay CCR2 Pre loaded registers on 
	
	TIM_Cmd(TIM3, ENABLE);  														// Can make TIM3
	

}

The header file timer.h The difference from the previous one is that TIM3_PWM_Init Statement of

#ifndef __TIMER_H
#define __TIMER_H
#include "sys.h"

void TIM3_Int_Init(u16 arr,u16 psc);
void TIM3_PWM_Init(u16 arr,u16 psc);
#endif

main.c

#include "led.h"
#include "delay.h"
#include "key.h"
#include "sys.h"
#include "usart.h"
#include "timer.h"

int main(void)
{
    		
 	u16 led0pwmval=0;
	u8 dir=1;	
	delay_init();	    	 								// Delay function initialization  
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); 	    // Set up NVIC Interrupt grouping 2:2 Bit preemption priority ,2 Bit response priority 
	uart_init(115200);	 									// The serial port is initialized to 115200
 	LED_Init();			     								//LED Port initialization 
 	TIM3_PWM_Init(899,0);	 								// Regardless of the frequency .PWM frequency =72000000/900=80Khz
   	while(1)
	{
    
 		delay_ms(10);	 
		if(dir)
		{
    
			led0pwmval++;
		}
		else
		{
     
			led0pwmval--;
		}

 		if(led0pwmval>300)
 		{
    
			dir=0;
		}
		if(led0pwmval==0)
		{
    
			dir=1;
		}										 
		TIM_SetCompare2(TIM3,led0pwmval);		   
	}	 
}

here , We can see from the dead cycle function that , We will led0pwmval This value is set to PWM It's worth , It's just It's through led0pwmval To control PWM Duty cycle of , Then control led0pwmval From 0 Change to 300, And then from 300 Change to 0, So circular , therefore DS0 The brightness will also change from dark to bright , And then it goes from light to dark . As for the In the value of the , Why do we take 300, Because PWM When the output duty cycle of reaches this value , our LED brightness There will be little change （ Although the maximum value can be set to 899）, Therefore, it is unnecessary to design too large a value here .