[time-nuts] Pictic II mods

Bob Camp lists at rtty.us
Fri Jul 2 19:50:46 EDT 2010


Hi

Yup, and as you go to higher baud rates the +/- one makes for a bigger "hop" in the baud rate. 

One cute way to attack the problem: 

Set the baud rate so it *should* be fast 
Set the PIC transmitter to send two stop bits (or marking parity and two stop bits if you can). 
Set the PC receiver to look for one stop bit and no parity. 

Net result is that you can tolerate a much higher baud rate error in a "transmit mostly" application like this one.

Bob


On Jul 2, 2010, at 5:44 PM, Stanley Reynolds wrote:

> yes, internal clock, may need to tune the osc or try +- one number, external osc 
> pins are in use.
> 
> Stanley
> 
> 
> 
> ----- Original Message ----
> From: Bob Camp <lists at rtty.us>
> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Sent: Fri, July 2, 2010 4:11:11 PM
> Subject: Re: [time-nuts] Pictic II mods
> 
> Hi
> 
> I believe he's using the internal clock on the PIC. It's not super accurate,
> so running a lot of data can be an issue.
> 
> Bob
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Stanley Reynolds
> Sent: Friday, July 02, 2010 3:41 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Pictic II mods
> 
> Looking at Richard's code in PICTICII.ASM :
> 
>    bsf     TXSTA,BRGH            ;set USART hi speed mode
>    movlw D'51'                         ;set async rate at 9600 baud (51. for
> 8 
> MHz int, BRGH=1)
>    movwf SPBRG
> 
> Then '25' would be 19,200 baud
> and '12' would be 38,400 baud
> 
> Need to test this but could be a way to get more data out.
> 
> Stanley
> 
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> 
> 
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