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funmix
Joined: 27 Mar 2007
Posts: 33
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| PIC to PIC via 232 |
 Posted: Tue Mar 27, 2007 11:26 am |
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Hi all,
I am new in ccs. I am trying to communicate between two PICs with UART.
So, the problem i would like to:
1. PIC master send a character 't'
2. Slave receive the character 't'; blink 1 time the Port B_1 LED.
3. Slave will send back character 's' to master once they finish blinking.
4. master check the character 's', if 's' is received, blink master PORT B_1 LED.
master.c
| Code: |
#include <18F4520.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOPUT,NOBROWNOUT
#use delay(clock=20000000)
#define BAUD_RATE 19200
#define FREQ_OSC 20000000
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//RB_1 -- Purple
//RB_2 -- Yellow
#byte PIR1 = 0x0c
#byte SPBRG = 0x99
#byte RCSTA = 0x18
#byte TXREG = 0x19
#byte RCREG = 0x1A
#byte TXSTA = 0x98
#bit TXIF = PIR1.4
#bit RCIF = PIR1.5
#bit CREN = RCSTA.4
#include <stdio.h>
//---------------------------------------
//Receive data interrupt
//------------------------------------
//------------------------
// Wait for the hardware UART's transmitter
// to become ready and then send the specified
// character.
void my_putc(char c)
{
while(!TXIF);
TXREG = c;
}
//------------------------
// Wait for character to be available from the
// hardware UART's receiver and then return it.
// If there is an overrun error, then clear it.
char my_getc(void)
{
int temp;
int retval;
while(!RCIF);
temp = RCSTA;
retval = RCREG;
if(bit_test(temp, 1))
{
CREN = 0;
CREN = 1;
}
return(retval);
}
//-------------------------
void init_uart(void)
{
SPBRG = (FREQ_OSC / (BAUD_RATE * 16)) -1;
TXSTA = 0x26;
RCSTA = 0x90;
}
#int_rda
void rda_isr(void)
{
char c;
c = my_getc();
if(c=='s')
{
output_high(PIN_B1);
delay_ms(5000);
output_low(PIN_B1);
delay_ms(5000);
}
//if(c=='r')
//{
//output_high(PIN_B2);
//delay_ms(5000);
//output_low(PIN_B2);
//delay_ms(5000);
//}
}
//================================
void main()
{
init_uart();
my_putc('t');
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
while(1);
}
|
slave.c
| Code: |
#include <18F4520.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOPUT,NOBROWNOUT
#use delay(clock=20000000)
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#include <stdio.h>
#include <slave_send.c>
//======================================slave
void main()
{
int i;char rec;
output_low(PIN_B1);
output_low(PIN_B2);
while(1)
{
wait_master(rec);
check_char(rec);
putc('s');
wait_master(rec);
check_char(rec);
//putc('r');
//wait_master(rec);
//check_char(rec);
}
}
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slave_send.c
| Code: |
void wait_master(char rec)
{
if (kbhit())
{
rec=getc();
}
}
void check_char(char rec)
{
if(rec=='t')
{
output_high(PIN_B1);//RB_1 -- Orange
delay_ms(5000);
output_low(PIN_B1);
delay_ms(5000);
}
//if(rec=='y')
//{
//output_high(PIN_B2);//RB_1 -- Orange
//delay_ms(5000);
//output_low(PIN_B2);
//delay_ms(5000);
}
}
|
For your information, my hardware connection got no problem. As i tested sending and echo a character with PC to PIC. |
|
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Mar 27, 2007 11:51 am |
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There are several things in your code that need to be improved.
For example, you have a #use rs232() statement, but then you
substitute your own functions for all the CCS functions. Why ?
In the routine below, you duplicate the functionality of getc(). The CCS
getc() function already waits for kbhit. It's part of the function.
| Code: | void wait_master(char rec)
{
if (kbhit())
{
rec=getc();
}
} |
In other words, your function above could be replaced by this single
line of code:
There's another problem with your routine above. You have these
two lines of code in your program, where it's clear that you expect
wait_master() to update the 'rec' value. But it won't do that.
| Code: | wait_master(rec);
check_char(rec); |
To get a value back from a function you need to return it (at least, that's
the easiest way to do it). You need to re-write the wait_master()
function so it returns a value. This is done with a 'return' statement.
Then your code would look like this:
| Code: |
rec = wait_master();
check_char(rec);
|
Or, the better way is to get rid of the wait_master() function completely,
as I said above, and do this:
| Code: | rec = getc();
check_char(rec); |
Your code might have other problems. But at least these things should
be fixed. |
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funmix
Joined: 27 Mar 2007
Posts: 33
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| Posted: Tue Mar 27, 2007 8:58 pm |
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here is my modified
master.c
| Code: |
#include <18F4520.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOPUT,NOBROWNOUT
#use delay(clock=20000000)
#define BAUD_RATE 19200
#define FREQ_OSC 20000000
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//RB_1 -- Purple
//RB_2 -- Yellow
#byte PIR1 = 0x0c
#byte SPBRG = 0x99
#byte RCSTA = 0x18
#byte TXREG = 0x19
#byte RCREG = 0x1A
#byte TXSTA = 0x98
#bit TXIF = PIR1.4
#bit RCIF = PIR1.5
#bit CREN = RCSTA.4
#include <stdio.h>
#include <master_check.c>
//-------------------------
void init_uart(void)
{
SPBRG = (FREQ_OSC / (BAUD_RATE * 16)) -1;
TXSTA = 0x26;
RCSTA = 0x90;
}
//================================
void main()
{
char rec;
init_uart();
putc('t');
delay_ms(6000);
rec=getc();
check_char();
putc('y');
delay_ms(6000);
rec=getc();
check_char();
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
while(1);
}
|
master_send.c
| Code: |
void check_char(void)
{
char rec;
if(rec=='r')
{
output_high(PIN_B1);//RB_1 -- Orange
delay_ms(5000);
output_low(PIN_B1);
delay_ms(5000);
}
if(rec=='s')
{
output_high(PIN_B2);//RB_1 -- Orange
delay_ms(5000);
output_low(PIN_B2);
delay_ms(5000);
}
}
|
slave.c
| Code: |
#include <18F4520.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOPUT,NOBROWNOUT
#use delay(clock=20000000)
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#include <stdio.h>
#include <slave_send.c>
//======================================slave
void main()
{
int i;char rec;
output_low(PIN_B1);
output_low(PIN_B2);
while(1)
{
rec=getc();
check_char();
delay_ms(6000);
putc('s');
rec=getc();
check_char();
putc('r');
delay_ms(6000);
}
}
|
slave_send.c
| Code: |
void check_char(void)
{
char rec;
if(rec=='t')
{
output_high(PIN_B1);//RB_1 -- Orange
delay_ms(5000);
output_low(PIN_B1);
delay_ms(5000);
}
if(rec=='y')
{
output_high(PIN_B2);//RB_1 -- Orange
delay_ms(5000);
output_low(PIN_B2);
delay_ms(5000);
}
}
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I am just doing vice-versa communication. I could not figure out why my code doesn't give me correct result.
Kindly please help. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Mar 27, 2007 9:10 pm |
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| Quote: | #include <18F4520.h>
#byte PIR1 = 0x0c
#byte SPBRG = 0x99
#byte RCSTA = 0x18
#byte TXREG = 0x19
#byte RCREG = 0x1A
#byte TXSTA = 0x98
#bit TXIF = PIR1.4
#bit RCIF = PIR1.5
#bit CREN = RCSTA
//-------------------------
void init_uart(void)
{
SPBRG = (FREQ_OSC / (BAUD_RATE * 16)) -1;
TXSTA = 0x26;
RCSTA = 0x90;
}
|
This demonstrates a very good reason why you should not use your
own routines. All of the register addresses listed above are for the
16F series PICs. The 18F series have different addresses.
I suggest that you use the CCS library code. Use the #use rs232()
statement, and use the built-in CCS UART functions. Most of your
problems will then go away. |
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funmix
Joined: 27 Mar 2007
Posts: 33
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| Posted: Tue Mar 27, 2007 11:01 pm |
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| Thanks for advice. Another things is, how to interrupt once the master microcontroller receive data from slave? |
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jecottrell
Joined: 16 Jan 2005
Posts: 559
Location: Tucson, AZ
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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