backlight.c

STM32综合例程（3.5.0固件库）

#include "stm32f10x.h"
#include <stdio.h>
#include "BackLight.h"

void SetBackLight(uint8_t _bright)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef  TIM_OCInitStructure;

	/* 第1步：打开GPIOB RCC_APB2Periph_AFIO 的时钟	*/
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);

	if (_bright == 0)
	{
		/* 配置背光GPIO为输入模式 */
		GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
		GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
		GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
		GPIO_Init(GPIOB, &GPIO_InitStructure);

		/* 关闭TIM3 */
		TIM_Cmd(TIM3, DISABLE);
		return;
	}
	else if (_bright == BRIGHT_MAX)	/* 最大亮度 */
	{
		/* 配置背光GPIO为推挽输出模式 */
		GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
		GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
		GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
		GPIO_Init(GPIOB, &GPIO_InitStructure);

		GPIO_SetBits(GPIOB, GPIO_Pin_1);

		/* 关闭TIM3 */
		TIM_Cmd(TIM3, DISABLE);
		return;
	}

	/* 配置背光GPIO为复用推挽输出模式 */
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOB, &GPIO_InitStructure);

	/* 使能TIM3的时钟 */
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

	/* -----------------------------------------------------------------------

	TIM3 ARR Register = 1894 => TIM3 Frequency = TIM3 counter clock/(ARR + 1)
	TIM3 Frequency = 37.99 KHz (接近38KHz 红外发射管的调制基频)
	TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR)* 100 = 50%
	----------------------------------------------------------------------- */

	/*
		TIM3 配置: 产生1路PWM信号;
		TIM3CLK = 72 MHz, Prescaler = 0(不分频), TIM3 counter clock = 72 MHz
		计算公式：
		PWM输出频率 = TIM3 counter clock /(ARR + 1)

		我们期望设置为100Hz

		如果不对TIM3CLK预分频，那么不可能得到100Hz低频。
		我们设置分频比 = 1000， 那么  TIM3 counter clock = 72KHz
		TIM_Period = 720 - 1;
		频率下不来。
	 */
	TIM_TimeBaseStructure.TIM_Period = 720 - 1;	/* TIM_Period = TIM3 ARR Register */
	TIM_TimeBaseStructure.TIM_Prescaler = 0;
	TIM_TimeBaseStructure.TIM_ClockDivision = 0;
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

	/* PWM1 Mode configuration: Channel1 */
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
	/*
		_bright = 1 时, TIM_Pulse = 1
		_bright = 255 时, TIM_Pulse = TIM_Period
	*/
	TIM_OCInitStructure.TIM_Pulse = (TIM_TimeBaseStructure.TIM_Period * _bright) / BRIGHT_MAX;	/* 改变占空比 */

	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
	TIM_OC4Init(TIM3, &TIM_OCInitStructure);
	TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

	TIM_ARRPreloadConfig(TIM3, ENABLE);

	/* TIM3 enable counter */
	TIM_Cmd(TIM3, ENABLE);
}