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neal1
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| any comment? |
 Posted: Thu Feb 26, 2009 7:51 am |
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I just wrote some code for serial communication with my PIC16f628a.
I just need some comment on my code...please comments.
I compiled these code with MPLAB v8.10 and no error occur.
Any comments are welcome:P
code as below:
| Code: | #include <ctype.h>
#include <16f628a.h>
#FUSES NOWDT, HS, NOPUT, NOPROTECT, BROWNOUT, MCLR, NOLVP, NOCPD
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_B2,rcv=PIN_B1,bits=8)
//#byte CMCON =0x1f
#byte CMCON = 0x1f
#byte portb = 0x06
#byte porta = 0x05
#byte RCSTA = 0x18
#byte Txreg = 0x19
#byte Rxreg = 0x1A
#bit RCIF = 0x0c.5 // PIR1 register,Flag bit RCIF will be set when reception is complete
#bit TXIE = 0x8c.4 //PIE register Flag bit TXIE is zero for Disables the USART transmit interrupt
#byte TXSTA = 0x98
#bit BRGH = TXSTA.2
#bit SYNC = TXSTA.4
#bit TXEN = TXSTA.5
#bit TX9 = TXSTA.6
#byte RCSTA= 0x18
#bit RX9 = RCSTA.6
#bit SPEN = RCSTA.7
#bit CREN = RCSTA.4
#byte SPBRG=0x99
void main()
{
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
setup_oscillator(False);
// TODO: USER CODE!!
output_low(portb);
output_low(porta);
CMCON =0x07; //enable pins for I/O function
SET_TRIS_A(0x00); //TRISA<5> always read as 1
SET_TRIS_b(0x02); //TRISB<1> bit needs to be set and TRISB<2> bit cleared in order to configure pins RB2/TX/CK and RB1/RX/DT as the Universal Synchronous Asynchronous Receiver Transmitter pins.
SPBRG=0x81; //129 decimal, using ASYNCHRONOUS MODE (BRGH = 1)
output_low(SYNC); //Asynchronous mode
output_high(TXEN); //Enable transmission
output_low(TX9); //enable 8bit transmittion
output_high(BRGH); //Asynchronous mode high speed
output_high(SPEN); //enable serial port receive
output_low(RX9); //enable 8 bit reception
output_high(CREN); //Enables continuous receive
output_low(portb);
output_low(porta);
while(1){
printf("srsrsrsr\n");
if (RCIF==1){
porta ='A';
}//end if
}//end while
}//end main |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Feb 26, 2009 12:36 pm |
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Comments:
1. Don't do direct register access. You don't need to do it.
Invoke the CCS library code with a #use statement, and
use CCS functions.
2. Before using CCS functions, read the manual on each function
and see how to properly use it.
http://www.ccsinfo.com/downloads/ccs_c_manual.pdf
3. Don't just "throw" code together. Understand every line, and
use the proper parameters for a function. In embedded
programming, everything is important. |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Thu Feb 26, 2009 1:20 pm |
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| Furthermore, if accessing SFR directly for some reason, do it according to the CCS C documentation. output_low() and output_high() are creating special code for IO ports, including direction register setup. They aren't intended for any other SFRs and most likely cause unexpected behaviour. They surely don't work with a byte address, as in your code. |
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neal1
Guest
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| Posted: Fri Feb 27, 2009 6:19 am |
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How about writing like this way? I simulate with MPSIM and seem work fine...
| Code: |
#include <ctype.h>
#include <16f628a.h>
#FUSES NOWDT, HS, NOPUT, NOPROTECT, BROWNOUT, MCLR, NOLVP, NOCPD
#use fast_io(a)
#use fast_io(b)
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_B2,rcv=PIN_B1,bits=8,ENABLE=PIN_B4)
int i;
void main()
{
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
setup_oscillator(False);
// TODO: USER CODE!!
output_a(0x00);
output_b(0x00);
SET_TRIS_A(0x00); //TRISA<5> always read as 1
SET_TRIS_b(0x02); //TRISB<1> bit needs to be set and TRISB<2> bit cleared in order to configure pins RB2/TX/CK and RB1/RX/DT as the Universal Synchronous Asynchronous Receiver Transmitter pins.
i=getc();
while(1){
printf("welcome\n");
printf("press 1 to Turn On LED1\n" );
printf("press 2 to Turn On LED2\n" );
switch(i){
case'1':
printf("LED1 Turned ON");
break;
case'2':
printf("LED2 Turned ON");
break;
/*if (kbhit())//wait until a character has been received
printf("hello!!\n");
else if (PIN_B3==1)
printf("hi!!\n");*/
}
}//end while
}//end main |
 BUT I NOT SURE CAN SWITCH THE 'i' CORRECTLY? |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Sun Mar 01, 2009 1:38 pm |
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| Code: | #use rs232(baud=9600,parity=N,xmit=PIN_B2,rcv=PIN_B1,bits=8,ENABLE=PIN_B4)
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Do you really require the ENABLE keyword? This is normally only used for switching the external bus drivers to a tri-state mode. Not a common thing to do in RS232, unless you are using another driver like RS485 of course. Skipping the enable function will free a hardware pin for other usage.
An improvement would be to add the ERRORS keyword. Without this keyword the hardware UART will freeze on a receive buffer overflow (3 characters).
Move this line inside the loop. For example, just before the switch statement. |
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