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deltatech
Joined: 22 Apr 2006
Posts: 87
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| CRC CODE Not Working need Help ! |
 Posted: Wed Aug 29, 2007 2:47 pm |
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Hi I am trying o run this code on Two Pics , On different CCS protyping boards . Both have a PIC16F877A one has 4MHz Crystal The other 10MHz Crystal
But When I run the code It keeps Printing "Hi There !" on the Hyperterminal .
but non of the other messages like
"Previous message sent was received by unit"
Can any one tell as to why this is not working as it shuld many thanks in advance
Hi there!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there
!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there
!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there
!‘a Hi there!‘a Hi there!‘a Hi there!‘a Hi there!‘a
#include "F:\Program Files\PICC\Project\CRC\CRC.h"
/////////////////////////////////////////////////////////////////////////
//// ////
//// This example program shows how to send messages between two ////
//// PICs using CRC error checking. Pushing a button on the ////
//// prototype card sends a message from that PIC to any other PICs ////
//// that are connected. The receiving PIC then sends back an ACK ////
//// after it correctly receives the message. ////
//// ////
//// Two seperate PICs are needed for this example. Compile the ////
//// code as is and program the first PIC. Then switch the ////
//// MACHINE_ADDRESS and SEND_ADDRESS and program the second PIC. ////
//// ////
//// ////
//// Packet Protocol: ////
//// +------------+--------------+---------+--------+------+-----+ ////
//// | Address TO | Address FROM | Control | Length | Data | CRC | ////
//// +------------+--------------+---------+--------+------+-----+ ////
//// ////
//// Address TO: 1 byte Address of sending PIC ////
//// Address FROM: 1 byte Address of receiving PIC ////
//// Control: 1 byte Used for ACK and NACK ////
//// Length: 2 bytes Number of bytes in Data field ////
//// Data: 0 to N bytes Data being sent ////
//// CRC: 2 bytes 16 Bit CRC ////
//// ////
//// Configure the CCS prototype card as follows: ////
//// Jumper from PIC 1 pin B0 to PIC 2 pin B1 ////
//// Jumper from PIC 1 pin B1 to PIC 2 pin B0 ////
//// Jumper from PIC 1 GND to PIC 2 GND ////
//// Jumper from PIC 1 Switch to PIC 1 pin B2 ////
//// Jumper from PIC 2 Switch to PIC 2 pin B2 ////
//// See additional connections below. ////
//// ////
//// This example will work with the PCM and PCH compilers. The ////
//// following conditional compilation lines are used to include a ////
//// valid device for each compiler. Change the device, clock and ////
//// RS232 pins for your hardware if needed. ////
| Code: | //#if defined(__PCM__)
//#include <16F877>
//#fuses HS,NOWDT,NOPROTECT,NOLVP
#fuses HS,NOWDT,NOPROTECT,PUT
//#use delay(clock=4000000)
//#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7)
//#use rs232(baud=9600, xmit=PIN_B2, rcv=PIN_B0)
/*
#elif defined(__PCH__)
#include <18F452>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_B1, rcv=PIN_B0)
#endif
*/
#include <crc.c>
// CONSTANTS
#define MACHINE_ADDRESS 0x01
#define SEND_ADDRESS 0x02
#define ACK 0x01
#define NACK 0xFF
#define BUFFER_SIZE 64
// GLOBAL VARIABLES
int packet_buffer[BUFFER_SIZE];
int ext_buffer[BUFFER_SIZE];
int ext_buffer_next_in;
int ext_buffer_next_out;
#define MESSAGE_SEND (!input(PIN_A4))
#define DATA_IN (ext_buffer_next_in != ext_buffer_next_out)
// EXTERNAL INTERRUPT
// function for reading in bytes from other PIC
#INT_EXT
void ext_isr()
{
ext_buffer[ext_buffer_next_in] = getc(); // get a byte, put it in buffer
if(++ext_buffer_next_in == BUFFER_SIZE) // increment counter
ext_buffer_next_in = 0;
}
// GET_BUFF_INT
// function to extract bytes from the buffer
int get_buff_int()
{
int retval;
while(!DATA_IN); // wait until data available
retval = ext_buffer[ext_buffer_next_out]; // get the byte
if(++ext_buffer_next_out == BUFFER_SIZE) // increment counter
ext_buffer_next_out = 0;
return retval;
}
// SEND_PACKET
// function to send a packet of data to another PIC
void send_packet(int* packet_ptr, int16 packet_length)
{
int *ptr;
int16 CRC,i;
ptr = packet_ptr; // set pointer
CRC = generate_16bit_crc(ptr, packet_length, CRC_CCITT);
// make CRC
for(i=0; i<packet_length>>8)); // send CRC
putc((int)(CRC));
}
// GET_PACKET
// function to get a packet from the buffer and read the data
short get_packet(int* packet_ptr)
{
short retval;
int16 length;
int16 CRC;
int16 i;
retval = TRUE;
packet_ptr[0] = get_buff_int(); // get the address of send to
packet_ptr[1] = get_buff_int(); // get the address of send from
if(packet_ptr[0] != MACHINE_ADDRESS)
retval = FALSE;
packet_ptr[2] = get_buff_int(); // get the control byte
if(packet_ptr[2] == NACK)
retval = FALSE;
packet_ptr[3] = get_buff_int(); // get the length of the data
packet_ptr[4] = get_buff_int();
length = (int16)(packet_ptr[3])<<8;
length += packet_ptr[4];
for(i=5; i<(length+5); i++) // get the data
packet_ptr[i] = get_buff_int();
packet_ptr[length+5] = get_buff_int(); // get the CRC
packet_ptr[length+6] = get_buff_int();
CRC = (int16)(packet_ptr[length+5])<<8;
CRC += packet_ptr[length+6];
if(CRC != generate_16bit_crc(packet_ptr, length+5, CRC_CCITT))
retval = FALSE;
return retval;
}
// Change RS-232 IO pins
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 6 to 14
void main() {
// lcd_init();
ext_buffer_next_in = 0; // init variables
ext_buffer_next_out = 0;
ext_int_edge(H_TO_L); // init interrupts
enable_interrupts(INT_EXT);
enable_interrupts(GLOBAL);
while(TRUE) // loop always
{
if(MESSAGE_SEND) // if button pushed
{
packet_buffer[0] = SEND_ADDRESS;
packet_buffer[1] = MACHINE_ADDRESS;
packet_buffer[2] = 0;
packet_buffer[3] = 0;
packet_buffer[4] = 9;
packet_buffer[5] = 'H';
packet_buffer[6] = 'i';
packet_buffer[7] = ' ';
packet_buffer[8] = 't';
packet_buffer[9] = 'h';
packet_buffer[10] = 'e';
packet_buffer[11] = 'r';
packet_buffer[12] = 'e';
packet_buffer[13] = '!';
send_packet(packet_buffer, 14); // send message
}
delay_ms(100);
if(!DATA_IN) // if no data in
continue; // loop back
if(get_packet(packet_buffer)) // if valid packet
{
int16 length,i;
// int16 CRC;
length = ((int16)(packet_buffer[3]<<8)) + packet_buffer[4];
if(packet_buffer[2] == ACK)
printf("Previous message sent was received by unit.\r\n");
if(length) // display message
{
printf("Message is:\r\n\n");
for(i=0; i<length; ++i)
putc(packet_buffer[i+5]);
}
printf("\r\n\n... Message End ...\r\n\n\n");
if(length)
{
packet_buffer[0] = packet_buffer[1];//send an ACK
packet_buffer[1] = MACHINE_ADDRESS;
packet_buffer[2] = ACK;
packet_buffer[3] = 0;
packet_buffer[4] = 0;
send_packet(packet_buffer, 5);
}
}
else // if not valid packet
{
if(packet_buffer[0] != MACHINE_ADDRESS)
break; // message is not for this PIC
else if(packet_buffer[2] == NACK) // tried to send and failed error
printf("Previous message sent was not received by unit.\r\n");
else
{ // tried to receive and failed error
printf("Message received was corrupted.\r\n");
packet_buffer[0] = packet_buffer[1];//send a NACK
packet_buffer[1] = MACHINE_ADDRESS;
packet_buffer[2] = NACK;
packet_buffer[3] = 0;
packet_buffer[4] = 0;
send_packet(packet_buffer, 5);
}
}
}
}
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Ttelmah
Guest
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| Posted: Wed Aug 29, 2007 2:58 pm |
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The code will print 'Hi there', if pin A4, is low. Have you got a pull-up resistor on this pin?. If not, then this is the answer...
Best Wishes |
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deltatech
Joined: 22 Apr 2006
Posts: 87
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| Posted: Wed Aug 29, 2007 3:10 pm |
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Hi Thanks but now I have changed PIN_A4 to PIN_C4 and it is still the same when i press the button It keeps Printing Hi There ! but nothing about The Machine Address etc
"Previous message sent was received by unit.\r\n" |
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Ttelmah
Guest
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| Posted: Wed Aug 29, 2007 3:26 pm |
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You still need a pull up resistor though....
Best Wishes |
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deltatech
Joined: 22 Apr 2006
Posts: 87
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| Posted: Wed Aug 29, 2007 5:13 pm |
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Thanks Ttelmah
I have just checked the board i have is a CCS Software Prototype Board and there is a 10k pull-up resistor connected to the push button . |
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