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che_chia
Joined: 09 May 2011
Posts: 6
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| RS-485 -- Can not Receive the data completely |
 Posted: Tue May 17, 2011 3:15 am |
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I can receive the data from transceiver completely.
Support it transmited 6 bytes (TXDbuffer[6]) in the transceiver, as
TXDbuffer[0] =0x01
TXDbuffer[1] =0x02
TXDbuffer[2] =0x03
TXDbuffer[3] =0x04
TXDbuffer[4] =161 // This value is got from CRC operation
TXDbuffer[5] =43 // This value is got from CRC operation
In my code, I can receive TXDbuffer[0]~TXDbuffer[4], but can't receive TXDbuffer[5] and TXDbuffer[6] currently. Should I clear the serial buffer?
My code as following:
| Code: |
#include <16F1947.H>
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT
#Fuses INTRC_IO
#use delay(clock=32000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, bits=8)
unsigned int uchCRCHi, uchCRCLo;
unsigned int8 TXDbuffer[6];
unsigned int8 RXDbuffer[6];
unsigned int8 RevCnt=0;
unsigned int const auchCRCHi[256] = {//CRC Matrix};
unsigned int const auchCRCLo[256] = {//CRC Matrix };
void xor_check(unsigned int *puchMsg, unsigned int crc_count)
{
unsigned int uindex;
uchCRCHi = 0xff;
uchCRCLo = 0xff;
while( crc_count )
{
uindex = uchCRCHi ^ *puchMsg;
puchMsg++;
uchCRCHi = uchCRCLo ^ auchCRCHi[uindex];
uchCRCLo = auchCRCLo[uindex];
crc_count--;
}
}
#INT_RDA
void serial_isr()
{
unsigned int RevTempData;
if( kbhit() )
{
RevTempData=getc();
if (RevCnt==0 && RevTempData==0x01)
{
RXDBuffer[0]=RevTempData;
RevCnt++;
}
else if (RevCnt>=1 && RevCnt<=5)
{
RXDBuffer[RevCnt]=RevTempData;
RevCnt++;
}
else if (RevCnt>=6)
{
RevCnt=0;
xor_check((unsigned int *)RXDBuffer, 4);
}
}
}
void main (void)
{
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
output_bit(PIN_G0,0);
while(1)
{}
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19513
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| Posted: Tue May 17, 2011 3:48 am |
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First, there is no need for the kbhit in the INT_RDA. The interrupt triggers _because_ there is a character ready to receive.
Second, add 'errors' to your RS232 declaration. This should _always_ be present when using the hardware RS232, unless _you_ are handling hardware overruns. without this the UART can become locked.
Now, big comments. You talk about TXDbuffer[6]. You have no such location in your buffer. In C, by default arrays are zero referenced. Your array is 0 to 5, does not have a location 6....
Then realistically, _do not_ perform the CRC operation in the UART code. You also don't seem to actually do anything with the calculated CRC. Checking it against the received value?. Asking for a re-transmission or throwing away the data if it is wrong?.
The code won't work properly as posted, since you send six bytes, but do not perform the CRC check, till a seventh arrives.
So, something like:
| Code: |
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, bits=8, ERRORS)
int1 have_packet=false;
#INT_RDA
void serial_isr() {
unsigned int RevTempData;
RevTempData=getc();
if (RevCnt==0 && RevTempData==0x01) {
RXDBuffer[0]=RevTempData;
RecvCnt++;
}
else {
if (Revcnt>=6) return; //throw data if buffer would overflow
RXDBuffer[RevCnt]=RevTempData;
RevCnt++;
if (RevCnt>=6) have_packet=true;
}
}
void main (void)
{
unsigned int8 localbuffer[6];
rs232_errors=0; //avoid compiler error message for rs232_errors
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
output_bit(PIN_G0,0);
do {
if (have_packet) {
disable_interrupts(INT_RDA);
memcpy(localbuffer,RXDbuffer,6);
have_packet=false;
RevCnt=0;
enable_interrupts(INT_RDA); //copy received dats to local storage, and
//start looking for the next packet
xor_check(local_buffer,4);
//need to modify the xor code to verify the CRC matches locations
//4, and 5, and do something if it doesn't....
}
} while (TRUE); //avoids compiler error message for while loop
}
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Best Wishes |
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