# Analog serial port-analog serial port Driver Based on gossip 8 common IO port

Source: Internet
Author: User

Analog serial port Driver Based on Listen 8 common IO port

The format of standard serial communication data is:Start bit (1) + Data bit (8) + check bit (1) + stop bit (1)

Another important part of serial communication is to set the baud rate,The baud rate is the number of bits transmitted by the serial port within one second.

Sampling frequency:In order to reduce the error of reading or sending serial data, we took the data read at a fixed position in the N (I used 4 times) interruption.

I use the 9600 baud rate calculation process in listen 8 as an example: (1 second transmission of 9600 bits)

It can be calculated that the time required for transmitting 1 bit T1 = 1/9600 is about104us

It can be seen that the interval between the timer interruption and the sending of one bit of data should be 104/4 = 26us (4x sampling frequency)

Stm8 internal crystal oscillator frequency is 16 m, I use 8 division, that is, 2 m, so the MCU shock cycle is 1/2 M =0.5us

From the above calculation, we can know that to send a bit of data, the initial value of the timer interrupt should be set to 26/0. 5 =52

The above is the calculation process of the relevant data. below is the simulation of the serial port driver and notes:

Timer interrupt and IO port configuration:

`void TIM3_Configuration(void){  TIM3_DeInit();  TIM3_TimeBaseInit(TIM3_PRESCALER_8,52);        //52  104  TIM3_ITConfig(TIM3_IT_UPDATE ,ENABLE);    TIM3_ARRPreloadConfig(ENABLE);  TIM3_Cmd(ENABLE);                                                //DISABLE TIM3_Cmd(DISABLE)}//模拟串口引脚定义#define SIM_UART_TX_PORT               GPIOC#define SIM_UART_TX_PIN                GPIO_PIN_2#define SimUartTxHigh()                (SIM_UART_TX_PORT->ODR |= (u8)(SIM_UART_TX_PIN))    #define SimUartTxLow()                 (SIM_UART_TX_PORT->ODR &= (u8)(~SIM_UART_TX_PIN)) #define SIM_UART_RX_PORT               GPIOC#define SIM_UART_RX_PIN                GPIO_PIN_3#define SimUartRxStatus()              (SIM_UART_RX_PORT->IDR & SIM_UART_RX_PIN)GPIO_Init(SIM_UART_RX_PORT, SIM_UART_RX_PIN,GPIO_MODE_IN_PU_NO_IT);         GPIO_Init(SIM_UART_TX_PORT, SIM_UART_TX_PIN,GPIO_MODE_OUT_PP_LOW_FAST);     `

`/* Includes ------------------------------------------------------------------*/#include "stm8s.h"#include "global.h"//默认采样频率为4倍  一下为16M晶振 8分频 后计数器的装载值//9600B 104us发送一位  4倍采样频率 故为26us发送一位#define  SIM_BAUDRATE_9600     52  #define  SIM_BAUDRATE_4800     104#define  SIM_BAUDRATE_2400     208/* Private variables ---------------------------------------------------------*/u8 RxByteIndex;        //接收字节索引u8 RxSampFreq;         //采样频率控制 1/4u8 TxXKCnt = 3;        //需要发送数据包的字节数u8 SimUartRxBuff[10];  //接收数据包缓冲u8 SimUartTxBuff[10] = {0x55, 0xaa, 0x66};bool IsSimUartRxFinish;//是否接收完成标志bool IsSimUartRecv;    //模拟串口是否处于接收状态/* Private functions ---------------------------------------------------------*//* Public functions ----------------------------------------------------------*/void <span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;">InterruptSimUart</span><span style="font-size: 12px; font-family: Arial, Helvetica, sans-serif;">(void);</span>static void Drv_SimUartTxByte(void);static void Drv_SimUartRxByte(void);/*******************************************************************************#Function      :   InterruptSimUart #Description   :   模拟串口中断调用程序  切换发送与接收#Parameter     :   NULL#Return        :   NULL#AuthorAndData :   huangzhigang 20141013*******************************************************************************/void InterruptSimUart(void){   if(IsSimUartRxFinish)   //接收完成后立刻发送数据  也可以自己定义什么时候发送数据   {           IsSimUartRxFinish = FALSE;      IsSimUartRecv = FALSE;   }      if(IsSimUartRecv)   {      Drv_SimUartRxByte();   }   else   {      Drv_SimUartTxByte();   }}/*******************************************************************************#Function      :   Drv_SimUartRxByte #Description   :   模拟串口接收函数#Parameter     :   NULL#Return        :   NULL#AuthorAndData :   huangzhigang 20141013*******************************************************************************/static void Drv_SimUartRxByte(void){    static u8 RxBitNum;    //接收位计数    static u8 Verify;      //校验码    static u8 OverTime;    //接收超时计数    static u8 s_u8Rxbuff;  //一字节接收缓存    if(SimUartRxStatus())    {        OverTime++;    }    else     {         OverTime = 0;    }    if(OverTime > 44)    {        OverTime = 45;        RxByteIndex = 0;        RxBitNum = 0;    }    if((SimUartRxStatus()) && (RxBitNum == 0))    {        RxSampFreq = 0;    }    else     {       ++RxSampFreq;       }    if(RxSampFreq == 1)    {        if(RxBitNum == 0)                                           //低电平，起始位bit0        {            if(!SimUartRxStatus())                                              {                Verify = 0;                s_u8Rxbuff = 0;                RxBitNum++;            }        }        else if((RxBitNum > 0) && (RxBitNum < 9))                   //数据位  bit1~8        {            if(SimUartRxStatus())                                   //高电平            {                s_u8Rxbuff = s_u8Rxbuff | (0x01 << (RxBitNum -1));                Verify++;            }            RxBitNum++;        }        else if(RxBitNum == 9)                                      //校验位  bit9        {            RxBitNum++;            if(Verify & 0x01)            {                if(SimUartRxStatus()) {RxBitNum = 0;}               //奇校验            }            else            {                if(!SimUartRxStatus()) {RxBitNum = 0;}                   }                    }        else if(RxBitNum == 10)                                     //停止位 bit10         {            if(SimUartRxStatus())                                                   {                RxBitNum = 0;                if(RxByteIndex == 0)                                //头码1为0X55                {                    if(s_u8Rxbuff == 0x55)                    {                        SimUartRxBuff[RxByteIndex] = s_u8Rxbuff;                        RxByteIndex++;                    }                    else                    {                        RxByteIndex = 0;                    }                                        //TEST  测试  接收到一字节数据后马上回复 //                    IsSimUartRxFinish = TRUE;                }                else if(RxByteIndex == 1)                           //头码2为0Xaa                {                    if(s_u8Rxbuff == 0xaa)                    {                        SimUartRxBuff[RxByteIndex] = s_u8Rxbuff;                        RxByteIndex++;                    }                    else                    {                        s_u8Rxbuff = 0;                    }                }                else                {                      SimUartRxBuff[RxByteIndex] = s_u8Rxbuff;                                                   RxByteIndex++;                      if(RxByteIndex >= 2)                            //接收完一个数据包                      {                         //TODO: 20141013 hzg 验证校验码                         RxByteIndex = 0;                         IsSimUartRxFinish = TRUE;                      }                }            }        }        else         {            RxBitNum = 0;        }    }    else if(RxSampFreq > 3)    {        RxSampFreq = 0;    }     }/*******************************************************************************#Function      :   Drv_SimUartTxByte #Description   :   模拟串口发送函数  #Parameter     :   NULL#Return        :   NULL#AuthorAndData :   huangzhigang 20141013*******************************************************************************/void Drv_SimUartTxByte(void){    static bool SendFinish = TRUE;  //发送完成标志    static u8 Verify;               //奇偶校验    static u8 TxSampFreq = 0;       //发送计数  采样4次    static u8 BitNum = 0;           //位计数    static u8 ByteLock;             //发送字节锁定（防止在发送途中 发送数字被改变）    static u8 TxIndex = 0;          //当前发送索引    if(SendFinish)    {       SendFinish = FALSE;       RxSampFreq = 0;       BitNum = 0;              if(TxIndex < TxXKCnt)        //控制发送的字节       {          ByteLock = SimUartTxBuff[TxIndex];          TxIndex++;          RxByteIndex = 0;       }       else                 {          IsSimUartRecv = TRUE;          SendFinish = TRUE;          TIM3->ARRH = (uint8_t)(52 >> 8);   //定时器3计数器重装初值          TIM3->ARRL = (uint8_t)(52);          //            TxXKCnt = 0;          TxIndex = 0;       }    }        if(++TxSampFreq > 3)    {        if(BitNum == 0)                             //起始位        {            Verify = 0;            SimUartTxLow();            BitNum++;        }        else if((BitNum >0) && (BitNum < 9))        //数据位        {            if(0x01 & (ByteLock >> (BitNum-1)))     //先发低位            {                SimUartTxHigh();                Verify++;            }            else            {                SimUartTxLow();            }            BitNum++;        }        else if(BitNum == 9)                        //校验位        {            if(0x01 & Verify)                       //奇校验              {                SimUartTxLow();                     //有奇数个1 则发送0             }            else            {                SimUartTxHigh();                    //有偶数个1则发送1            }            BitNum++;        }        else if(BitNum == 10)                       //停止位        {            SimUartTxHigh();            SendFinish = TRUE;            BitNum = 0;        }                TxSampFreq = 0;    }}`

Analog serial port-analog serial port Driver Based on gossip 8 common IO port

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