RS232 Baud Rate

[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.