 |
 |
| View previous topic :: View next topic |
| Author |
Message |
hadeelqasaimeh
Joined: 05 Jan 2006
Posts: 105
|
| out ascii on port b |
 Posted: Wed Jul 26, 2006 12:24 am |
 |
|
hi all
i need to out charachters on portb and recieve them on other pic (both are 16f874) but its dosent work,,,here is the TX code
| Code: |
#include <16F877a>
#include "string.h"
#include "lcd_kbd1.c"
#fuses XT,NOWDT,NOPROTECT
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#byte tris_b =0x00
int f;
int value;
static char MX[6];
void main()
{
strcpy(MX,"1");
output_b(0x00);
//value=0x25;
while(TRUE)
{
delay_ms(2000);
output_b (MX);
}//while(true)
}//main
|
and here is the RX code
| Code: |
#include <16F877a>
#include "string.h"
#include "lcd_kbd1.c"
#fuses XT,NOWDT,NOPROTECT
#use delay(clock=4000000)
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#byte tris_b =0xff
static char RX[15];
int1 f;
int8 i,value;
void main()
{
f=0;
LCD_Init();
while(TRUE) {
//if(f==1) {
value=input_b();
LCD_PutCmd ( CLEAR_DISP );
LCD_SetPosition ( LINE_16_1);
printf(LCD_PutChar,"RX is");
LCD_SetPosition ( LINE_16_2);
printf(LCD_PutChar," %d",value);
delay_ms(1000);
}//while |
thanx alot |
|
 |
Ttelmah
Guest
|
|
| Posted: Wed Jul 26, 2006 2:47 am |
|
|
There is nothing to synchronise the transactions. You cannot be sure when the PICs actually start, and if one leads the other by a small amount of time, the data will always be corrupted. This is why 'asynchronous' communications (like RS232), have a 'start' bit, to mark where the transaction starts. Seperately, what you are actually 'sending', is the low byte of the address where the array is stored, not the array contents...
Do something like this:
| Code: |
//TX
//Need processor setup etc., here.
char MX[6];
//You do not need the static declaration for a 'global'.
void main(void) {
int8 ctr;
strcpy(MX,"1234");
while (TRUE) {
//output a 'marker'
output_b(0xAA);
delay_ms(1);
//Now switch to the 'start of transmission' marker
output_b(0x55);
for (ctr=0;ctr<6;ctr++) {
//Now send the characters
output_b (MX[ctr]);
delay_ms(1);
} //for
output_b(0);
//ensure we are not sending the 'marker' bytes
delay_ms(1000);
} //while
}//main
//RX
char RX[6]; //Only needs to be the same size as the TX buffer
void main(void) {
int8 ctr;
//On _both_chips, you should add any code to turn off things like
//the adc here.
LCD_Init();
while(TRUE) {
while (input_b() != 0x55);
//wait for the first marker
while (input_b() == 0x55);
//Now the main code is moving to start sending the data
delay_us(500);
//delay long enough for the first byte to be present.
for (ctr=0;ctr<6;ctr++) {
//get the bytes at 1mSec pacing
RX[ctr]=input_b();
delay_ms(1);
}//for
//At this point the 'transaction' has been received
LCD_PutCmd ( CLEAR_DISP );
LCD_SetPosition ( LINE_16_1);
printf(LCD_PutChar,"RX is");
LCD_SetPosition ( LINE_16_2);
printf(LCD_PutChar," %s",RX);
//No delay here, need to get back, and start waiting for the next
//message.
}//while
}//main
|
The key is that the receiver waits till it sees the 'AA' character, and then waits for this to change. At this moment, the transmitter will start sending a few uSec latter (the time it takes to setup the counter, and access the array), and will send the characters at just over 1mSec intervals. The receiver waits 500uSec, so the first character should have arrived, and then reads six characters at the same basic pacing. Any slight errors in the timings of the two loops, willbe handled by the fact that we should be just about in the 'middle' of the character time.
Best Wishes |
|
|
rnielsen
Joined: 23 Sep 2003
Posts: 852
Location: Utah
|
|
| Posted: Wed Jul 26, 2006 10:01 am |
|
|
It appears that you might be trying to communicate similar to a parallel port. You would need to have a Strobe signal, from the TX PIC, to tell the RX PIC when to look at it's port. Probably hook it up to an interrupt pin would work.
Ronald |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
