HSER baudrate

[pedja089]

Hello,
I'm not very familiar with the hardware serial port. So far I have used define.
But when I tried this:

HSerBaud var byte
IF HSerBaud=0 THEN
 DEFINE HSER_BAUD 300
ENDIF
IF HSerBaud=1 THEN
   DEFINE HSER_BAUD 2400
ENDIF
IF HSerBaud=$BD THEN
   DEFINE HSER_BAUD 9600
ENDIF

I got an error, Redefininig symbor that can not be redefined...
I do not know what registers should be set to change the baud rate.
If you can help, so I would not read the whole datasheet. I'm using PIC18LF14K50.
Thanks

[Archangel]

That's is correct as far as I know, you cannot redefine it in running code, you can however select it in the beginning as your PIC starts. Look at the code example in the lower 1/2 of this article. I show you how to do it there.

http://www.picbasic.co.uk/forum/content.php?r=171-LCD-serial-backpacks

[mackrackit]

If you need to change the baud rate during run time do not use defines. Deal with the registers directly.

X VAR WORD
    START:
     RCSTA.4 = 0 : RCSTA.4 = 1
     RCSTA=$90:TXSTA=$24:SPBRG=129
     HSERIN [dec X]
     HSEROUT [DEC X.7,13]
blah
blah

[Archangel]

or there's Dave's way . . .

[mister_e]

When changing baudrate on the fly, you want to turn off the USART before though.

RCSTA=0
SPBRG=xyz
TXSTA = whatever, assuming it's value change from baudrate to baudrate
RCSTA=$90

[pedja089]

Thanks, guys.
Both examples helped me. Just to see which registers should be set. Today I'll try ..

[mister_e]

Get the latest version of my PICMultiCalc on this forum, it will give you a good kick.

[pedja089]

Everything works great. The calculator has really helped me.
Here's the code if someone needs it.

             IF HSerBaud=0 THEN
                RCSTA = 0
                SPBRG = 207 ' 300 Baud @ 4MHz, 0.0% 
                RCSTA = $90 ' Enable serial port & continuous receive
                TXSTA = $20 ' Enable transmit, BRGH = 0
             endif   
             IF HSerBaud=1 THEN
                RCSTA = 0
                SPBRG = 25  ' 2400 Baud @ 4MHz, 0.17%
                RCSTA = $90 ' Enable serial port & continuous receive
                TXSTA = $20 ' Enable transmit, BRGH = 0
             endif
             IF HSerBaud=$BD THEN
                RCSTA = 0
                SPBRG = 25  ' 9600 Baud @ 4MHz, 0.16%
                RCSTA = $90 ' Enable serial port & continuous receive
                TXSTA = $24 ' Enable transmit, BRGH = 1
             endif

[mister_e]

For safety sake, I would set RCSTA at the end, just after TXSTA.

[pedja089]

Done. But I don't see what difference it makes.
Can someone explain?

[mister_e]

It shouldn't make so much difference, but it's a bit more logical to me

1. You disable the USART
2. You set the baudrate and mode
3. You Enable the USART

Open the datasheet, and see what else you do when you write 0 or $90 to RCSTA, it does more than just enable/disable the USART.

[pedja089]

I looked into datasheet, and saw to change a bunch of thing. I just need to reset and set the seventh bit RCSTA to turn off and on UART
Is there a way to use the parity bit. Suppose 2400.8, E, 1, or 9600.8, E, 1 As I see hardware support and the ninth bit. The PBP I saw that there define the ninth bit.
If I add this to the beginning of the code
DEFINE HSER_EVEN 1
DEFINE HSER_BITS 9
How will changes in RCSTA, TXSTA,SPBRG registers affect hserin or serout.

[mister_e]

RCSTA, TXSTA, SPBRG will override the DEFINE and configure the PIC USART. It doesn't affect Serout, Serout2 or DEBUG. Those are software solution.

Again check out the USART section about Parity.

[pedja089]

I continue where I left off ...
This is code:

         define OSC 4
        OSCCON=%01010110

DEFINE HSER_CLROERR 1 'Hser clear overflow automatically 
'        SPBRG = 25  ' 9600 Baud @ 4MHz, 0.16%
'        TXSTA = $24 ' Enable transmit, BRGH = 1
'        RCSTA = $90 ' Enable serial port & continuous receive
DEFINE HSER_BAUD 9600        'Set Baud rate to 9600bps
DEFINE HSER_BITS 9        'Set to 9 bit mode
DEFINE HSER_EVEN 1        'Set Even Parity

TRISB.7 = 0 'Make Tx output
TRISB.5 = 1 'Make Rx input

main:
 pause 1000
 HSerOut ["Parity:)"]
goto main

Use this or not

DEFINE HSER_BITS 9        'Set to 9 bit mode
DEFINE HSER_EVEN 1        'Set Even Parity

Always get a 9600, N, 1. PIC never send parity bit.
I'm banging head all day, but I can't catch what I missed.

[pedja089]

Problem solved, thanks to Darrel.
I find solution in this topic.