RS232 Baud Rate

Hi Everyone;

I made this program and works fine at 9600 or 2400bps, however if i put at for exemple 57600 or 19200, i don't receive the the chars correctly, can somebody help me;

PIC16F877A
4Mhz

Thanks

Code:

Code:

include "modedefs.bas" DEFINE OSC 4 ' VARIÁVEIS ' ==================================================================== DADOS var byte(4) ID var byte(2) ' REGISTOS PINOUT 1 = IN; 0 = OUT ' ==================================================================== '76543210 TRISA = %00000001 TRISB = %00001111 TRISC = %10000000 TRISD = %00000000 TRISE = %00000000 ADCON1 = 7 ' NOMES PINOUT ' ==================================================================== LED VAR PORTA.1 TX Var PORTC.6 RX VAR PORTC.7 ' DEFINIÇÕES ' ==================================================================== DEFINE LCD_DREG PORTB ' LCD Data bits on PORTB DEFINE LCD_DBIT 4 ' PORTB starting address DEFINE LCD_RSREG PORTB ' LCD RS bit on PORTB DEFINE LCD_RSBIT 3 ' LCD RS bit address DEFINE LCD_EREG PORTB ' LCD E bit on PORTB DEFINE LCD_EBIT 2 ' LCD E bit address DEFINE LCD_BITS 4 ' LCD in 4-bit mode DEFINE LCD_LINES 2 ' LCD has 2 rows DEFINE LCD_COMMANDUS 2000 ' Set command delay time in us DEFINE LCD_DATAUS 50 ' Set data delay time in us DEFINE HSER_RCSTA 90h DEFINE HSER_TXSTA 24h DEFINE HSER_BAUD 9600 DEFINE HSER_SPBRG 25 ' INICIO PROGRAMA ' ==================================================================== Start: LCDOUT $fe, 1 lcdout " Teste USB" lcdout $FE,$C0," Por Hugo Oliveira" pause 2000 Main: toggle led hserout ["Hugo "] lcdout " Teste USB" lcdout $FE,$C0," Hugo " Pause 2000 toggle led hserout ["Oliveira",cr] LCDOUT $fe, 1 lcdout " Teste USB" lcdout $FE,$C0," Oliveira " Pause 2000 low led ' Rotina que espera por trama, ID, e Valor e compara ' ==================================================================== Recebe: Hserin [wait("OK"),STR ID\2,str DAdos\4] if id(0)="3" and id(1)="2" then if DADOS(0)="H" and DADOS(1)="u" and DADOS(2)="g" and DADOS(3)="o" then high led LCDOUT $fe, 1 lcdout " Teste USB" lcdout $FE,$C0,"Recebido H " endif if DADOS(0)="L" and DADOS(1)="u" and DADOS(2)="L" and DADOS(3)="u" then low led LCDOUT $fe, 1 lcdout " Teste USB" lcdout $FE,$C0,"Recebido L " endif if DADOS(0)<>"L" and DADOS(0)<>"H" then LCDOUT $fe, 1 lcdout " Teste USB" lcdout $FE,$C0,"Recebido :",DADOS(0),DADOS(1),DADOS(2),DADOS(3) endif endif goto Recebe END

More speed :)

Quote:

Originally Posted by gadelhas

PIC16F877A
4Mhz

Hi
If you need higher baudrate than 9600 you really must change oscillator speed to something higher. In this case more is better :)

Hi Again,

I change this 2 lines;

Code:

include "modedefs.bas" DEFINE OSC 4

for this;

Code:

DEFINE OSC 4 include "modedefs.bas"

And now i have tested with success this baud rates;
HSER_BAUD - HSER_TXSTA
300 - 20h
600 - 20h
1200 - 20h
2400 - 24h
4800 - 24h
9600 - 24h
14400 - 24h
19200 - 24h
28800 - 24h

38400 and 57600, tested, but without success.
PIC16F877A-I/P
4Mhz

Regards

Quote:

Originally Posted by sinoteq

Hi
If you need higher baudrate than 9600 you really must change oscillator speed to something higher. In this case more is better :)

Hi sinoteq,
Thanks for your answer, however int he datasheet, it says that it will work up to 57600 with 4mhz oscilator.
I allready teste with success baud rates higher than 9600, as you can see in my previous post.

Pic Multicalc

Hi,

Do a search for Pic Multicalc, it's very useful for setting up the defines etc. Entering an osc of 4Mhz and 3400 or 57600 it gives these values

Code:

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1 DEFINE HSER_SPBRG 6 ' 38400 Baud @ 4MHz, -6.99% DEFINE HSER_CLROERR 1 ' Clear overflow automatically DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0 DEFINE HSER_SPBRG 0 ' 57600 Baud @ 4MHz, 8.51% DEFINE HSER_CLROERR 1 ' Clear overflow automatically

You could try these values, however for running at a fast baud rate I would recommend using a 20Mhz crystal on the 16F877A with the following defines

Code:

@ __config _HS_OSC DEFINE OSC 20 DEFINE HSER_BAUD 115200 ' Hser baud rate DEFINE HSER_RCSTA 90h ' Hser receive status init DEFINE HSER_TXSTA 24h ' Hser transmit status init DEFINE HSER_SPBRG 10 ' 115200 Baud @ 20MHz, -1.36% DEFINE HSER_CLROERR 1 ' Hser clear overflow automatically

Quote:

Originally Posted by malc-c

Hi,

Do a search for Pic Multicalc, it's very useful for setting up the defines etc. Entering an osc of 4Mhz and 3400 or 57600 it gives these values

Code:

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1 DEFINE HSER_SPBRG 6 ' 38400 Baud @ 4MHz, -6.99% DEFINE HSER_CLROERR 1 ' Clear overflow automatically DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0 DEFINE HSER_SPBRG 0 ' 57600 Baud @ 4MHz, 8.51% DEFINE HSER_CLROERR 1 ' Clear overflow automatically

You could try these values, however for running at a fast baud rate I would recommend using a 20Mhz crystal on the 16F877A with the following defines

Code:

@ __config _HS_OSC DEFINE OSC 20 DEFINE HSER_BAUD 115200 ' Hser baud rate DEFINE HSER_RCSTA 90h ' Hser receive status init DEFINE HSER_TXSTA 24h ' Hser transmit status init DEFINE HSER_SPBRG 10 ' 115200 Baud @ 20MHz, -1.36% DEFINE HSER_CLROERR 1 ' Hser clear overflow automatically

Hi Again, ad thanks again for your reply;

Hi allready used the Pic Multicalc exactly like you post here, however at 38400 and 57600, don´t work Maybe my serial port don't accept that % of error.

I don' thave a 20Mhz oscilator, i'm going to buy one and then i will make more test.

Thanks to all.