CCS C Compiler Manual PCB / PCM / PCH

Common Questions & Answers
How can I use two or more RS-232 ports on one PIC®?
The #USE RS232 (and I2C for that matter) is in effect for GETC, PUTC, PRINTF and KBHIT
functions encountered until another #USE RS232 is found.
The #USE RS232 is not an executable line. It works much like a #DEFINE.
The following is an example program to read from one RS-232 port (A) and echo the data to
both the first RS-232 port (A) and a second RS-232 port (B).
#USE RS232(BAUD=9600, XMIT=PIN_B0, RCV=PIN_B1)
void put_to_a( char c ) {
put(c);
}
char get_from_a( ) {
return(getc()); }
#USE RS232(BAUD=9600, XMIT=PIN_B2,RCV=PIN_B3)
void put_to_b( char b ) {
putc(c);
}
main() {
char c;
put_to_a("Online\n\r");
put_to_b("Online\n\r");
while(TRUE) {
c=get_from_a();
put_to_b(c);
put_to_a(c);
}
}
The following will do the same thing but is more readable and is the recommended method:
#USE RS232(BAUD=9600, XMIT=PIN_B0, RCV=PIN_B1, STREAM=COM_A)
#USE RS232(BAUD=9600, XMIT=PIN_B2, RCV=PIN_B3, STREAM=COM_B)
main() {
char c;
fprintf(COM_A,"Online\n\r");
fprintf(COM_B,"Online\n\r");
while(TRUE) {
c = fgetc(COM_A);
fputc(c, COM_A);
fputc(c, COM_B);
}
}
How can the RB interrupt be used to detect a button press?
The RB interrupt will happen when there is any change (input or output) on pins B4-B7. There is
only one interrupt and the PIC® does not tell you which pin changed. The programmer must
determine the change based on the previously known value of the port. Furthermore, a single
button press may cause several interrupts due to bounce in the switch. A debounce algorithm
will need to be used. The following is a simple example:
#int_rb
rb_isr() {
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