RS232 Baud Rate

[gadelhas]

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:

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

[sinoteq]

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 :)

[gadelhas]

Hi Again,

I change this 2 lines;

include "modedefs.bas"
DEFINE OSC 4

for this;

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

[gadelhas]

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.

[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



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



@ __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

[gadelhas]

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



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



@ __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.