ARM®mbed OS入门开发 STM32内置CRC模块的使用十进制转二进制

anywill 提问时间：2016-10-21 13:50 /

本帖最后由 anywill 于 2016-10-21 13:52 编辑

所有的STM32芯片都内置了一个硬件的CRC计算模块，可以很方便地应用到需要进行通信的程序中，这个CRC计算模块使用常见的、在以太网中使用的计算多项式：
X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 +X8 + X7 + X5 + X4 + X2+ X +1
写成16进制就是：0x04C11DB7

使用这个内置CRC模块的方法非常简单，

用四个开关表示十进制转二进制:
#include "mbed.h"
/*

Last chage: 21-03-2014

Project Name:  NUCLEO-F070R-DigIN-CRC-DEC to BIN

By:          www.emcu.it - Enrico Marinoni

NOTE: see here: http://www.emcu.it/NUCLEOevaBoards/NUCLEOevaBoards.html#Tutorial

This program show this functionality:
      USART2 (Virtual Com for debug)
      USART1
      DigitalIn
      Decimal to Binary conversion//十进制转二进制
      CRC calculation
NOTE:
      A jumper must be present from PB_6 to PA_10 (USART1)
      More details  are available here:
      http://www.emcu.it/NUCLEOevaBoards/mBed/QSG-Mbed-Library.pdf

  VARIABLEs

  IO Status -> variable name is: IOStatus
      Name Bit Directions  Note
      Din1 0 IN       PB_8
      Din2 1 IN       PB_9
      Din3 2 IN       PA_6 - Not used in this release of FW
      Din4 3 IN       PA_7 "    "    "    "
      RL1    4 OUT       PA_8 Optional 4 Relay shield from SEED STUDIO - Not used in this release of FW
      RL2    5 OUT       PB_10 "    "    "    "    " -    "    "    "    "
      RL3    6 OUT       PB_4    "    "    "    "    " -    "    "    "    "
      RL4    7 OUT       PB_5    "    "    "    "    " -    "    "    "    "

  ADC Status - Not used in this release of FW
      Name    Variable Name  Note
      Ain0       ValAin0    PA_0 - Not used in this release of FW
      Ain1       ValAin1    PA_1    "    "    "    "
      Ain2       ValAin2    PA_4    "    "    "    "
      Ain3       ValAin3    PB_0    "    "    "    "
      Ain4       ValAin4    PC_1    "    "    "    "

  USART2 (RX==D0 - PA_3, TX==D1 - PA2) it is used for debug (connected to the PC) using TeraTerm.
  USART1 (RX==D2 - PA_10 , TX==D10 - PB_6) it is used for show the way to use another USART.
  Both USART are used in RX Interrupt mode.
  The USART parameters are:
Baud Rate: 1200
Data: 8
Parity: NONE
Stop: 1
Flow Control: NONE

*/

Serial pc(SERIAL_TX, SERIAL_RX); // This is USART2 tx, rx
                                 //    It is used for Debug via VirtualCOM
                                 //
Serial Serial1(PB_6, PA_10);       // This is USART1 tx, rx暂时无用

DigitalOut myled(LED1);          // This LED is on NUCLEO-F070R

DigitalIn BlueButton(USER_BUTTON);  // This is Blue-Button and is on NUCLEO-F070R
// Digital InPut - from the field
DigitalIn Din1(PB_8);
DigitalIn Din2(PB_9);
DigitalIn Din3(PA_6);
DigitalIn Din4(PA_7);

#define Pressed 0
#define NotPressed 1
#define Enable 1
#define Disable 0
#define POLYNOMIAL 0xD8  /* Is for CRC calculation - 11011 followed by 0's */

int Car='\0';
int CarSerial1='\0';
int n=0;
int DinStatus = 0;
int ValCRC = 0;

// Functions -----------------------------------------------------------------------
void SendToPCtheDinStatusAndCRC(void);

int ReadIO(void);    // Read and return the Din1...4 status

void ConvDecToBin(int); // Convert Decimal number in Binary and send the result
                     //    to the PC

uint8_t crcNaive(uint8_t const);

void callback2() // PC - USART2 used for Debug
{
// Note: you need to actually read from the serial to clear the RX interrupt
Car = pc.getc();
}

void USART1_INT() // USART1
{
// Note: you need to actually read from the serial to clear the RX interrupt
CarSerial1 = Serial1.getc();
}

// Interrupt used for flashing the Green Led
Timeout to1;
#define ON 1
#define OFF 0
#define DLYFlash 0.5
int ONOFF_Flashing = ON;
void IntFlash(void);

// MAIN program ---------------------------------------------------------------------
int main() {

// Define the USART ports
Serial1.attach(&USART1_INT);
pc.attach(&callback2);

// SetUp the baud rate
pc.baud(1200);
Serial1.baud(1200);

// Set PullUp on Digital Input Pins (Din1...4)
Din1.mode(PullUp);
Din2.mode(PullUp);
Din3.mode(PullUp);
Din4.mode(PullUp);

// Start flashing the Green Led
ONOFF_Flashing = ON;             // Enabling flashing flag
to1.attach(&IntFlash, DLYFlash);  // Enabling flashing Interrupt

pc.printf("\n\r\n\r START MAIN - NucleoF334R8-DigIN-CRC-DECtoBIN\n\r");

while(1) // Main infinite loop --------------------------------------------------
{

// Test the Blue Button
if (BlueButton == Pressed)
      {
      while(BlueButton == Pressed)
         {
         if (n == 0)
            pc.printf("Please release the BLUE Button\n\r");
         n++;
         }
      n = 0;
      pc.printf("The Digital Input status are:\n\r");
      DinStatus = ReadIO();
      pc.printf("DinStatus == %x\n\r", DinStatus);
      pc.printf("Din4 Din3 Din2 Din1\n\r");
      ConvDecToBin(DinStatus);

      // CRC calculation
      ValCRC = crcNaive(DinStatus);
      pc.printf("CRC == %d\n\r", ValCRC);

      ONOFF_Flashing = OFF; // Disable Interrupt of Green LED

      // Start flashing the Green Led (enable Interrupt)
      ONOFF_Flashing = ON;             // Enabling flashing flag
      to1.attach(&IntFlash, DLYFlash);  // Enabling flashing Interrupt

      }

// Test the char. received from PC - USART2 that is USB Virtual COM
if (Car == 'E')
      {
         pc.printf("\n\r - Send char. E (received from USB_VirtualCOM PC-USART2) to USART1\n\r");
         pc.printf(" - If there is a jumper from PB_6 to PA_10, you will see the Din4...1 status + CRC\n\r");
         Serial1.putc('E');  // Send char. E to USART1
         Car = '\0';
      }

if (Car == '?')
      {
         // Send to PC the status of Digital Inputs Din1...4
         SendToPCtheDinStatusAndCRC();
         Car = '\0';
      }

// Test the char. received from AUREL (USART1)
if (CarSerial1 == 'E')
      {
         pc.printf("RX char. E from USART1\n\r");
         // Send to PC the status of Digital Inputs Din1...4
         SendToPCtheDinStatusAndCRC();
         CarSerial1 = '\0';
      }
}
// END Main infinite loop -------------------------------------------------------
}

void SendToPCtheDinStatusAndCRC(void)
{
ONOFF_Flashing = OFF; // Disable Interrupt of Green LED
pc.printf("\n\r- PC request, to know the Digital Inputs Status\n\r");
DinStatus = ReadIO();
pc.printf("DinStatus == %x\n\r", DinStatus);
pc.printf("Din4 Din3 Din2 Din1\n\r");
ConvDecToBin(DinStatus);
// CRC calculation
ValCRC = crcNaive(DinStatus);
pc.printf("CRC related to Din4...1 == %d\n\r", ValCRC);
Car = '\0';
// Start flashing the Green Led (enable Interrupt)
ONOFF_Flashing = ON;             // Enabling flashing flag
to1.attach(&IntFlash, DLYFlash);  // Enabling flashing Interrupt
}

int ReadIO(void)
{
DigitalIn Din1(PB_8);
int DinValue=255;

/* Read all the Digital Inputs (Din1...4) and return a DinValue

      DinValue (bit)          Note
         0             Din1 - 1 == OPEN, 0 == CLOSE
         1             Din2 -    "       "
         2             Din3 -    "       "
         3             Din4 -    "       "
*/

// Test Din1 status
if (Din1 == 0)
      DinValue = DinValue & 254; // 0
else
      DinValue = DinValue & 255; // 1

// Test Din2 status
if (Din2 == 0)
      DinValue = DinValue & 253; // 0
else
      DinValue = DinValue & 255; // 1

// Test Din3 status
if (Din3 == 0)
      DinValue = DinValue & 251; // 0
else
      DinValue = DinValue & 255; // 1

// Test Din4 status
if (Din4 == 0)
      DinValue = DinValue & 247; // 0
else
      DinValue = DinValue & 255; // 1

return DinValue;
}

//
// Function that convert a Decimal number in Binary
// the original function is here:
// http://www.programmingsimplified ... t-decimal-to-binary
//
void ConvDecToBin(int n)
{
int c, k;
for (c = 3; c >= 0; c--)
{
      k = n >> c;

      if (k & 1)
         pc.printf("  1  ");
      else
         pc.printf("  0  ");
}
pc.printf("\n\r");
}

//
// Function that flashing the Green Led
//
void IntFlash(void)
{
if (ONOFF_Flashing == ON)
      myled = !myled;
else
      myled = 0;
to1.detach();
to1.attach(&IntFlash, DLYFlash); // this line reload Interrupt
}

//
// CRC calculation
// Original code is gere: http://www.barrgroup.com/Embedde ... -Calculation-C-Code
//
uint8_t crcNaive(uint8_t const message)
{
uint8_t  remainder;

/*
   * Initially, the dividend is the remainder.
   */
remainder = message;

/*
   * For each bit position in the message....
   */
for (uint8_t bit = 8; bit > 0; --bit)
{
      /*
      * If the uppermost bit is a 1...
      */
      if (remainder & 0x80)
      {
         /*
         * XOR the previous remainder with the divisor.
         */
         remainder ^= POLYNOMIAL;
      }

      /*
      * Shift the next bit of the message into the remainder.
      */
      remainder = (remainder << 1);
}

/*
   * Return only the relevant bits of the remainder as CRC.
   */
return (remainder >> 4);

}