Bill Stoddart wrote 2012-03-23 00:03:
> Hello,
> This feels like a simple question but I've had very little luck finding a=
ny
> answers.
>
> I have an 18F4550 on the PICDEM FSUSB board. It has a 20Mhz crystal. I am
> trying to send data out over rs232. I have gotten everything working at
> 9600 baud but this is just barely able to keep up with my data source
> (clocked in from an FPGA).
>
> I have been programming with the hi-tech compiler and MPLAB.
>
> Code for the usart:
> OpenUSART(USART_TX_INT_OFF&  USART_RX_INT_OFF&  USART_ASYNCH_MODE&
> USART_EIGHT_BIT&  USART_CONT_RX&  USART_BRGH_LOW, 78);
>
> Header code:
> #define _XTAL_FREQ 20000000  // (20 MHz crystal on PICDEM FS USB board)
>
> #pragma config PLLDIV   =3D 5
> #pragma config CPUDIV   =3D OSC1_PLL2
> #pragma config USBDIV   =3D 2
> #pragma config FOSC     =3D HSPLL_HS
>
> I would appreciate any help calculating out the numbers for a higher spee=
d.
> I have been shooting for 115200 with out any luck. I've gone through the
> datasheet but i'm lost.
> Thanks in advance.
> Bill

Can you get it working with some simple assembler code?
Should just take 10-15 lines to make a short USART test to
send something out. Then, with the params worked out, one
can/could translate them into whatever high-level language
one is using.



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