W5500 adjusts the brightness of LED light band through upper computer control

The experiment uses W5500 The development board sends commands to the development board through the upper computer to control the brightness of the external light strip ; The main process is as follows ：

1  The experiment purpose

The upper computer sends through serial port in the format of :“redbrightness,greenbrightness,bluebrightness” String to MCU.MCU Convert the number into the corresponding brightness .

2  The overall design of the experiment

The experiment is mainly divided into two parts ：PWM Configuration and serial communication configuration . The difficulty of the whole experiment lies in ASCII The process of converting codes into numbers .

3 PWM The principle of production

Universal timers can be used GPIO Pin for pulse output . To make STM32 Universal timer TIMx produce PWM Output , Need to use 3 A register . Namely ： Capture / Compare mode register （TIMx_CCMR1/2）、 Capture / Compare enable register （TIMx_CCER）、 Capture / Compare register （TIMx_CCR1~4）.（ Be careful , There's another. TIMx Of ARR Registers are used to control pwm The output frequency of ）.

For capture / Compare mode register （TIMx_CCMR1/2）, This register has 2 individual ,TIMx _CCMR1 and TIMx _CCMR2.TIMx_CCMR1 control CH1 and 2, and TIMx_CCMR2 control CH3 and 4. The second is capture / Compare enable register （TIMx_CCER）, This register controls the switch of each input and output channel .

Finally, capture / Compare register （TIMx_CCR1~4）, This register has 4 individual , Corresponding 4 Two transmission channels CH1~4.4 The functions of registers are similar , It's all used to set up pwm The duty cycle of . for example , If pulse counter is configured TIMx_CNT Count up for , Overloaded registers TIMx_ARR Be configured as N, namely TIMx_CNT The current count value of X stay TIMxCLK Under the drive of clock source, it keeps accumulating , When TIMx_CNT The numerical X Greater than N when , Reset TIMx_CNT Values for 0 Recount . And in the TIMxCNT While counting ,TIMxCNT The count of X Will compare register with TIMx_CCR Pre stored values A Compare , When the pulse counter TIMx_CNT The numerical X Less than comparison register TIMx_CCR Value A when , Output high level （ Or low level ）, By contraries , When the value of the pulse counter X Greater than or equal to the value of the compare register A when , Output low level （ Or high level ）. So circular , The output pulse period obtained is the overload register TIMx_ARR Stored values (N+1) Times the clock period of the trigger , Its pulse width is a comparison register TIMx_CCR Value A Times the clock period of the trigger , The output PWM The duty cycle of is A/(N+1) .

4  PWM Configuration steps

4.1  To configure GPIO

void LED_Config(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

 

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC|RCC_APB2Periph_AFIO, ENABLE);// Turn on multiplex clock

 

GPIO_InitStructure.GPIO_Pin =  LED_RED| LED_BLUE | LED_GREEN;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

 

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOC, &GPIO_InitStructure);

 

GPIO_SetBits(GPIOC, LED_RED | LED_BLUE | LED_GREEN);

}

4.2  Configure timer

void TIMER_Config(void)

{

TIM_TimeBaseInitTypeDef     TIM_BaseInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

 

GPIO_PinRemapConfig(GPIO_FullRemap_TIM3, ENABLE);

 

TIM_BaseInitStructure.TIM_Period = 255;

TIM_BaseInitStructure.TIM_Prescaler = 0;

TIM_BaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;

TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;

 

TIM_TimeBaseInit(TIM3, &TIM_BaseInitStructure);

TIM_ARRPreloadConfig(TIM3, ENABLE);

TIM_Cmd(TIM3, ENABLE);

}

4.3  To configure PWM

void PWM_Config(void)

{

TIM_OCInitTypeDef  TIM_OCInitStructure;

 

TIM_OCStructInit(&TIM_OCInitStructure);

TIM_OCInitStructure.TIM_Pulse = 0;

TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM1;              // Choice mode 1

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low      // Polarity is active at high level

 

TIM_OC2Init(TIM3, &TIM_OCInitStructure);

TIM_OC3Init(TIM3, &TIM_OCInitStructure);

TIM_OC4Init(TIM3, &TIM_OCInitStructure);

 

TIM_OC2PreloadConfig(TIM3,TIM_OCPreload_Enable);

TIM_OC3PreloadConfig(TIM3,TIM_OCPreload_Enable);

TIM_OC4PreloadConfig(TIM3,TIM_OCPreload_Enable);

 

TIM_CtrlPWMOutputs(TIM3,ENABLE);

 

}

4.4  Summary

PWM Pattern 1：

When counting up , once TIMx_CNTTIMx_CCR1 Time channel 1 Is the invalid level (OC1REF=0), Otherwise, it is the effective level (OC1REF=1).

PWM Pattern 2：

When counting up , once TIMx_CNTTIMx_CCR1 Time channel 1 Is the effective level , Otherwise, it is invalid level .

At the same time, the effective comments output are also related to the polarity configuration ：

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

This configuration is that the high level is the effective level , vice versa .

5         UART Configuration steps

5.1          To configure UART1 And corresponding GPIO

void Usart_Config(uint32_t BaudRate)

{

GPIO_InitTypeDef GPIO_InitStructure;

USART_InitTypeDef USART_InitStructure;

 

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

 

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;

GPIO_Init(GPIOA, &GPIO_InitStructure);

 

 

USART_InitStructure.USART_BaudRate = BaudRate;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

 

USART_Init(USART_PC, &USART_InitStructure);

 

USART_ITConfig(USART_PC, USART_IT_RXNE, ENABLE);  // Open serial port receive interrupt

USART_ITConfig(USART_PC, USART_IT_IDLE, ENABLE);  // Open serial port receive interrupt

 

USART_Cmd(USART_PC, ENABLE);

}

5.2  Configuration interrupt

void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

 

 

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);

 

 

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

5.3  Interrupt function

void USART1_IRQHandler(void)

{

uint8_t clear = clear;

 

if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)

{

USART_ClearITPendingBit(USART1, USART_IT_RXNE);

 

RxBuffer[RxCounter++] = USART_ReceiveData(USART1);

}

else if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET)

{

clear = USART1->SR;

clear = USART1->DR;      // First reading SR read DR, To clear away IDLE interrupt

RxNumber = RxCounter;

RxCounter = 0;            // Counter reset

IDLE_Flag = 1;        // Mark the received data of one frame

}

}

5.4  Summary

STM32 Single chip microcomputer can receive variable length byte data . because STM32 MCU with IDLE interrupt , Take advantage of this interrupt , Can receive variable length bytes of data . because STM32 Belong to ARM Single chip microcomputer , So the method of this article is also suitable for other ARM Single chip microcomputer .

IDLE After receiving a frame of data through the serial port , The interruption that happened . For example, send it to MCU once 1 Bytes , Or one time 8 Bytes , These data from one time , It's called one frame data , It can also be called a packet of data .  At the end of a frame of data , It will produce IDLE interrupt . This interrupt is very useful , It can save a lot of trouble of judgment .

6 ASCII Code to number

6.1  Implementation steps ：

 

while(RxBuffer[i] !=  ','){     i++;  len++;}// If not for ',' The length of the add 1

 

for(j=i-len; j

value = RxBuffer[j]&0x0f;         // take ascii Code to number

pwm_red += value * Power(len-1);

len--;

}

i++;

len = 0;

 

 

while(RxBuffer[i] !=  ','){         i++;  len++;}

 

for(j=i-len; j

value = RxBuffer[j]&0x0f;         // take ascii Code to number

pwm_green += value * Power(len-1);

len--;

}

 

i++;

len = 0;

 

 

while(RxBuffer[i] !=  '\0'){      i++;  len++;}

 

for(j=i-len; j

value = RxBuffer[j]&0x0f;         // take ascii Code to number

pwm_blue += value * Power(len-1);

len--;

}

 

RedOutput(pwm_red);

GreenOutput(pwm_green);

BlueOutput(pwm_blue);

 

pwm_red = 0;

pwm_green = 0;

pwm_blue = 0;

 

for(i=0; i<11; i++)               RxBuffer[i] = NULL;// Clear array

 

i = 0;

len = 0;

}

}

}

6.2 10 Of n The power function

uint8_t Power(uint8_t pow)

{

uint8_t i;

uint8_t sum = 1;

 

for(i=0; i

 

return sum;

}