modbus RTU với pic cần giúp đỡ

[hoc_picpicpic]

chào các huynh, em viết chương trình modbus RTU slave trên pic16f877a nhưng crc gửi đi ko đúng, em có tham khảo cách tính crc trong tài liệu http://forums.ni.com/attachments/ni/...I_MBUS_300.pdf .

huynh nao làm rồi giúp em xem sai ở đâu.

trình tự em test như sau :


Modbus Master send:

0x01 address Slave
0x04 function 4
0x00 address start byte hight
0x01 address start byte low
0x00
0x04 quantity
0xA0 crc hight
0x09 crc low



Modbus Sleve Respond: (pic16f877a)

01 04 08 00 00 00 00 00 00 00 00 40 0B


huynh nào có cách tính crc khác chỉ giúp em với ạ

[hoc_picpicpic]

còn đây là chương trình:


#include <16F877A.h>
#fuses HS, NOWDT ,PROTECT ,NOBROWNOUT ,NOPUT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6,rcv=PIN_C7,bits=8, stop=2, parity=N)





int1 modbus_flag_status;

int8 modbus_index = 0;
int8 modbus_data_transmit[10];
int8 modbus_data_reciever[10];

//---------------------------------------
int16 modbus_calcu_crc(int8 *puchMsg, int16 usDataLen);
//---------------------------------------
void main()
{
int8 i ;
int8 quantity ;
int16 modbus_crc ;


enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);

for(i=0;i<10;i++ )
{
modbus_data_transmit[i] = 0;
};


while(TRUE)
{

if( modbus_flag_status == 1 ) // test function 4
{
modbus_flag_status = 0;


putchar( modbus_data_reciever[0]); // adress slave
putchar( modbus_data_reciever[1]); // function

quantity = modbus_data_reciever[5]*2 ;

putchar(quantity); // byte count

for(i=0;i<quantity;i++)
{
putchar( modbus_data_transmit[i] ); // data byte
};


modbus_crc = modbus_calcu_crc(modbus_data_transmit, quantity); // crc calculate

putchar( modbus_crc >> 8 ); // crc hight byte
putchar( modbus_crc); // crc low byte

};


}
}
//-----------------------------------------------------------
int16 modbus_calcu_crc(int8 *puchMsg, int16 usDataLen)
{


//---------------------------------------
/* Table of CRC values for high–order byte */
const unsigned char modbus_CRCHi[] = {
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x01,0xC0, 0x80,0x41,0x00,0xC1,0x81,
0x40,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x00, 0xC1,0x81,0x40,0x01,0xC0,
0x80,0x41,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40, 0x00,0xC1,0x81,0x40,0x01,
0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x01,0xC0,0x80, 0x41,0x01,0xC0,0x80,0x41,
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x00,0xC1, 0x81,0x40,0x00,0xC1,0x81,
0x40,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x01, 0xC0,0x80,0x41,0x01,0xC0,
0x80,0x41,0x00,0xC1,0x81,0x40,0x00,0xC1,0x81,0x40, 0x01,0xC0,0x80,0x41,0x01,
0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x01,0xC0,0x80, 0x41,0x00,0xC1,0x81,0x40,
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x01,0xC0, 0x80,0x41,0x00,0xC1,0x81,
0x40,0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x00, 0xC1,0x81,0x40,0x01,0xC0,
0x80,0x41,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40, 0x00,0xC1,0x81,0x40,0x01,
0xC0,0x80,0x41,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81, 0x40,0x01,0xC0,0x80,0x41,
0x00,0xC1,0x81,0x40,0x00,0xC1,0x81,0x40,0x01,0xC0, 0x80,0x41,0x00,0xC1,0x81,
0x40,0x01,0xC0,0x80,0x41,0x01,0xC0,0x80,0x41,0x00, 0xC1,0x81,0x40,0x01,0xC0,
0x80,0x41,0x00,0xC1,0x81,0x40,0x00,0xC1,0x81,0x40, 0x01,0xC0,0x80,0x41,0x01,
0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x00,0xC1,0x81, 0x40,0x01,0xC0,0x80,0x41,
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x01,0xC0, 0x80,0x41,0x00,0xC1,0x81,
0x40
};

/* Table of CRC values for low–order byte */
const unsigned char modbus_CRCLo[] = {
0x00,0xC0,0xC1,0x01,0xC3,0x03,0x02,0xC2,0xC6,0x06, 0x07,0xC7,0x05,0xC5,0xC4,
0x04,0xCC,0x0C,0x0D,0xCD,0x0F,0xCF,0xCE,0x0E,0x0A, 0xCA,0xCB,0x0B,0xC9,0x09,
0x08,0xC8,0xD8,0x18,0x19,0xD9,0x1B,0xDB,0xDA,0x1A, 0x1E,0xDE,0xDF,0x1F,0xDD,
0x1D,0x1C,0xDC,0x14,0xD4,0xD5,0x15,0xD7,0x17,0x16, 0xD6,0xD2,0x12,0x13,0xD3,
0x11,0xD1,0xD0,0x10,0xF0,0x30,0x31,0xF1,0x33,0xF3, 0xF2,0x32,0x36,0xF6,0xF7,
0x37,0xF5,0x35,0x34,0xF4,0x3C,0xFC,0xFD,0x3D,0xFF, 0x3F,0x3E,0xFE,0xFA,0x3A,
0x3B,0xFB,0x39,0xF9,0xF8,0x38,0x28,0xE8,0xE9,0x29, 0xEB,0x2B,0x2A,0xEA,0xEE,
0x2E,0x2F,0xEF,0x2D,0xED,0xEC,0x2C,0xE4,0x24,0x25, 0xE5,0x27,0xE7,0xE6,0x26,
0x22,0xE2,0xE3,0x23,0xE1,0x21,0x20,0xE0,0xA0,0x60, 0x61,0xA1,0x63,0xA3,0xA2,
0x62,0x66,0xA6,0xA7,0x67,0xA5,0x65,0x64,0xA4,0x6C, 0xAC,0xAD,0x6D,0xAF,0x6F,
0x6E,0xAE,0xAA,0x6A,0x6B,0xAB,0x69,0xA9,0xA8,0x68, 0x78,0xB8,0xB9,0x79,0xBB,
0x7B,0x7A,0xBA,0xBE,0x7E,0x7F,0xBF,0x7D,0xBD,0xBC, 0x7C,0xB4,0x74,0x75,0xB5,
0x77,0xB7,0xB6,0x76,0x72,0xB2,0xB3,0x73,0xB1,0x71, 0x70,0xB0,0x50,0x90,0x91,
0x51,0x93,0x53,0x52,0x92,0x96,0x56,0x57,0x97,0x55, 0x95,0x94,0x54,0x9C,0x5C,
0x5D,0x9D,0x5F,0x9F,0x9E,0x5E,0x5A,0x9A,0x9B,0x5B, 0x99,0x59,0x58,0x98,0x88,
0x48,0x49,0x89,0x4B,0x8B,0x8A,0x4A,0x4E,0x8E,0x8F, 0x4F,0x8D,0x4D,0x4C,0x8C,
0x44,0x84,0x85,0x45,0x87,0x47,0x46,0x86,0x82,0x42, 0x43,0x83,0x41,0x81,0x80,
0x40
};


int8 uchCRCHi, uchCRCLo ;
int16 uIndex ;
int16 i ;


uchCRCHi = 0xFF ;
uchCRCLo = 0xFF ;

for(i=0;i < usDataLen ;i++ )
{
uIndex = uchCRCHi ^ *puchMsg++ ;
uchCRCHi = uchCRCLo ^ modbus_CRCHi[uIndex];
uchCRCLo = modbus_CRCLo[uIndex] ;
};

i = uchCRCHi ;
i = (i<<8) | uchCRCLo ;


return(i);


}
//-----------------------------------------------------------
#INT_RDA
void interrupt_rs232(void)
{
char data ;

data = getchar();

modbus_data_reciever[modbus_index] = data;

modbus_index++ ;
if( modbus_index >= 8 )
{
modbus_flag_status = 1;
modbus_index = 0;

};

//putchar(data);


}

[lovedt]

không ai trả lời cả!

[SLPRV]

Có 1 ví dụ khi viết trên C#:
Với chuỗi "01 03 00 01 00 04". Ta khai báo 1 mảng byte mang[];
Hãy gán giá trị cho mảng như sau: mang[0] = Convert.ToByte("01",16) ....và tiếp tục với
các giá trị còn lại còn lại.
chuỗi truyền có 6 byte nên "len = 6";
Khi sử dụng thì hãy gọi hàm ModRTU_CRC(mang,len);

UInt16 ModRTU_CRC(byte[] buf, int len)
{
UInt16 crc = 0xFFFF;

for (int pos = 0; pos < len; pos++) {
crc ^= (UInt16)buf[pos]; // XOR byte into least sig. byte of crc

for (int i = 8; i != 0; i--) { // Loop over each bit
if ((crc & 0x0001) != 0) { // If the LSB is set
crc >>= 1; // Shift right and XOR 0xA001
crc ^= 0xA001;
}
else // Else LSB is not set
crc >>= 1; // Just shift right
}
}
// Note, this number has low and high bytes swapped, so use it accordingly (or swap bytes)
return crc;