Thread: PIC16F876 's USART

i am doing project use a PIC16F876 to control motor.
Compiler is Mplap.

this program should print a > prompt character when first started and whenever it is ready to accept a new command.

after running this program,
the following things are occur:
>/nÙ>/nÙ>/nÙ>/nÙ>çzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ï
zr
ù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/
nÙ
>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/
nÙ
>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ï
zr
ù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/
nÙ
>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ�j·m>~�j·�j·�j·�j·o>~�j·�j·�j·�j·ù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù
½¹
e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù
½¹
e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù
½¹
e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>
/n
Ù>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>Ïzrù½ÿ>/n>/n~>/nv>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/n
Ù>
/nÙ>/nÙ>/nÙžzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙžzrù½¹ùù
½¹
Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙžzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/
nÙ
>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙžzrù½¹ùù½¹Ùù½¹e>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/nÙ>/n
Ù>
/nÙ>/nÙ>>>>>Ÿ>€>ƒ>î>>p>v>ƒ>¸>»>p>Æ>w>†>ã>·>6>|>¾>¾>ß>s> ö>ï>ž>ûžòò2òúóóór>>p>v>
ƒ>
¸>»>p>Æ>w>†>ã>·>6>|>¾>¾>ß>s>ö>ï>ž>ûžòò2òúóóór>>p>v >ƒ>¸>»>p>Æ>w>†>ã>·>6>|>¾>¾>ß
>s
>ö>ï>ž>ûžòò2òúóóór>>p>v>



Why? thanks!

#include <pic.h>
#include <stdio.h>
#include "pwm.h"

#define Fosc (4000000L)

void sendByte(char c);
unsigned char adcChannel = 1;
const char string[] = ">";

void initUSART()
{

BRGH = 0; // high speed data rate "Fosc/(16(X+1))
SPBRG = 207;
SYNC = 0; //asnchronous serial port
SPEN = 1; //enable serial port pins
CREN = 1; //enable reception
RCIE = 0; //disable rx interrupts
TXIE = 0; //disable tx interrupts
TX9 = 0; //8-bit transmission
RX9 = 0; //8-bit reception
TXEN =1; //enable transmission
}

void sendBytes(const char *tx)
{
while( *tx != 0 )
{
sendByte(*tx++);
}
}

void sendByte(char c){
/* Wait until TXIF == 0 */
while (0==TXIF);

/* Now set TXREG */
TXREG = c;
}

unsigned char getByte()
{
if (OERR)
{
CREN = 0;
CREN = 1;
}
if (RCIF)
return RCREG;
else return 0x00;
}
void pwm_init500()
{
PR2 = 0b01111100; //PERIOD OF 500HZ. FROM ONLINE FREQUENCY CALCULATOR
CCPR1L= 0b00001100; //duty cycle = 40%
//CCPR1L= 0x80;
TRISC2 = 0;
CCP1CON = 0b00000011;
T2CKPS1 = 1; //SETTING PRESCALER OF 1:16
TMR2ON = 1; //TIMER 2 ON BIT.
}
/*motor forward running*/
void forward()
{
RA0=0;
RA1=1;
RA2 = 1;
}

/*main function*/
main(){

unsigned char temp;
unsigned char f;

ADFM = 1;
TRISC = 0;

TRISA = 0;

initUSART();
pwm_init500();
sendBytes(string);

if(RCIF)
{
temp = getByte();
sendByte(temp);
if(temp = f) forward();

}
}

I don't know if this is related to your bug, but:

>if(temp = f) forward();
Should be:
if(temp == f) forward();

>if (OERR)
>{
>CREN = 0;
>CREN = 1;
>}

What's the purpose of this?

Function main should return a value.

I updated my program.

Usart can make microcontroller to communicate with host computer.

this program was compiled well. compile is mplap.

but nothing display on Terminal.


#include <pic.h>
#include <stdio.h>
#include "pwm.h"

#define Fosc (4000000L)
// Function declaration

void adc_read(unsigned char channel);
void initUSART();
void sendBytes(const char *tx);
char *getInput();
unsigned char getByte();
void pwm_init500();
void forward();
void reverse();
void stop();
void sendByte(char c);
void main(){

unsigned char temp;
char *str1;

ADFM = 1;
TRISC = 0;

TRISA = 0;
initUSART();
pwm_init500();
// sendBytes(string);

while(1)
{
str1 = getInput();
sendBytes(str1);
}

/* temp = getByte();
while(temp
temp = getByte();
if(RCIF){
sendByte(getByte);
if(temp == 'f') forward();
*/
}

void adc_read(unsigned char channel)
{
ADCON0 = (channel <<3) + 0xC1;
ADGO = 1;
while(ADGO)
continue;
}

void initUSART()
{

BRGH = 0; // high speed data rate "Fosc/(16(X+1))
SPBRG = 207;
SYNC = 0; //asnchronous serial port
SPEN = 1; //enable serial port pins
CREN = 1; //enable reception
RCIE = 0; //disable rx interrupts
TXIE = 0; //disable tx interrupts
TX9 = 0; //8-bit transmission
RX9 = 0; //8-bit reception
TXEN =1; //enable transmission
}

void sendBytes(const char *tx)
{
while( *tx != 0 )
{
sendByte(*tx++);
}
}

void sendByte(char c){
/* Wait until TXIF == 0 */
while (0==TXIF);//TXIF indicates the status TXREG -wait for TXREF to be empty

/* Now set TXREG */
TXREG = c;
}

unsigned char getByte()
{
if (OERR) //Overrun Error bit(can be cleared by clearing bit CREN)
{
CREN = 0;
CREN = 1;
}
if (RCIF)
return RCREG;
else return 0x00;
}

// try to get character from keyboard
char *getInput()
{
char * buff;
char temp;
int i;
temp = getByte();
while (temp != 13) // "13" is enter key
{
*(buff+i) = temp;
i++;
temp = getByte();
}
*(buff+i) = '\0';
return buff;
}
void pwm_init500()
{
PR2 = 0b01111100; //PERIOD OF 500HZ. FROM ONLINE FREQUENCY CALCULATOR
CCPR1L= 0b00001100; //duty cycle = 40%
//CCPR1L= 0x80;
TRISC2 = 0;
CCP1CON = 0b00000011;
T2CKPS1 = 1; //SETTING PRESCALER OF 1:16
TMR2ON = 1; //TIMER 2 ON BIT.

}

void forward()
{
RA0=0;
RA1=1;
RA2 = 1;
}
void reverse()
{
RA0=1;
RA1=0;
}
void stop()
{
RA0=RA1;
}

main(){

unsigned char temp;
char *str1;


ADFM = 1;
TRISC = 0;

TRISA = 0;

initUSART();
pwm_init500();
// sendBytes(string);

while(1)
{
str1 = getInput();
sendBytes(str1);
}

/* temp = getByte();
while(temp
temp = getByte();
if(RCIF){
sendByte(getByte);
if(temp == 'f') forward();
*/
}

Please use code tags