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PIC16F876 USART: Please Help

 
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mhjami
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PIC16F876 USART: Please Help
PostPosted: Thu Feb 15, 2007 2:04 pm     Reply with quote

Hi all,
i am using a low power digital radio (ER400TRS) to send some character from PC to PIC. PIC will then decode the data and control peripheral devices. a small c program is running on computer which sends ASCII characters of key 2,4,6,8. the wireless link works fine and i can see decimal ASCII value 50 when i press key 2 from remote computer. now i have connected a PIC16F876 with the receiver end. an led is connected with pin c0 and c1. i have implemented a test program for pic which will receive this ascii value and turn led on if any key being press from remote computer. i have followed the example program to buffer the data and interrupt service. codes are as follows

# include <16F876.h>
# use delay (clock=4000000) // 4Mhz clock
# fuses XT,NOWDT, NOPROTECT, NOPUT, NOBROWNOUT
# use rs232(baud=9600, rcv=PIN_C7, parity=N, BITS=8, ERRORS) // initalizing usart

// for Buffer configaration

# define B_SIZE 32
int8 BUFFER[B_SIZE];
int8 B_IN = 0;
int8 B_OUT = 0;

# define out_pin PIN_C0

// Inturrept routine for receiveing serial data

#int_rda

int8 serial_isr()
{ // start of routine

int8 temp;

BUFFER [B_IN]=getc();
temp=B_IN;
B_IN=(B_IN+1)% B_SIZE;

if (B_IN==B_OUT)
B_IN=temp;
} // end of routine


#define BCOND (B_IN!=B_OUT)

int8 serial_data()
{ //start of serial_data
int8 temp_data;
while (!BCOND)
temp_data=BUFFER[B_OUT];
B_OUT=(B_OUT+1)% B_SIZE;
return (temp_data);

} // end of serial data


// main program

void main ()
{ //start of main function

int8 data;
enable_interrupts(global); // Global interrupt
enable_interrupts(int_rda); // interrupt for serial data

data=serial_data();

switch (data){ // start of switch


case 50:
output_high(out_pin);
delay_ms(100);
output_low(out_pin);

break;

case 52:
output_high(out_pin);
delay_ms(100);
output_low(out_pin);
break;
case 54:
output_high(out_pin);
delay_ms(100);
output_low(out_pin);
break;
case 56:
output_high(out_pin);
delay_ms(100);
output_low(out_pin);
break;


default: output_high(PIN_C1);
delay_ms(100);
output_low(PIN_C1);
break;

} // end of switch



} // end of main

but nothing is happening on the pic. if i press computer key 2,4,6,8 no led becomes on. pls help me. where i made mistake. looking for any kind advice.
with regards
mhjami
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Thu Feb 15, 2007 6:11 pm     Reply with quote

Code:
# use rs232(baud=9600, rcv=PIN_C7, parity=N, BITS=8, ERRORS) // initalizing usart
Also add the Tx pin definition on PIN_C6. I haven't tested it, but I guess when either the Tx or Rx pin is missing the CCS compiler will generate a software UART. A software UART can't generate interrupts and hence your code is not working.
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