fast serial communication and pic

[mwmmboy]

Did someone used the pic16f877 for serial communication at 115.2 Kbaud?
Did you had some problems?

TX.

 

[admir]

Hi,

Almost everybody use that speed with PIC without problems. I am using it in bootloader in combination with MAX232 which works OK. I assume your PIC is running at 20MHz. Can you post schematics?

 

[mwmmboy]

thanks Admir,
the schematic is simple, but I have anotehr question. I usualy use PIC with the oscillator in the external cristal configuration, what is the best frequency of the cristal to use to go 115.2?

Thanks.

 

[Zedman]

Hi,

there is a formula in the 87x datasheet at page 97
(USART baud rate generator, baud rate formula),
you can calculate the exact crystal for 115k with it.
You can minimize the error factor using closer crystals,
but it's running fine at 115k for me with 10 or 20MHz too.
You also have to check framing/overrun errors in software
if you want realiable communication.

good luck,
Zed

 

[mwmmboy]

Many thanks Zedman,
I usually program PIC using C and when I have to receive a serial protocol I check the overrun error only on the first byte received and at 19200 baud I have no problem at all.
Plaese can you indicate me a good C code to implement a receiving function ith check for framing and overrun error?

Bye