Communicate with PC at baud rate :115200 bps

[iugmoh]

Hi all,
I woking on project communicate with Nokia 5110 through serial protocol , but I have a problem that the serial protocol must be at baud rate 115200 bps , so I try PC with PIC16f877a first. I can communicate at 9600 with higher than this the data is not true it's corrupted .
if anyone can help me ?

[Archangel]

Hello iugmoh,
Need a little more information, over what distance, what kind of wire are you using, are you using max 232 level shifters chips, are you using hand shaking, what oscillator speed is the PIC running, are you using serout, serout2, hserout . . . ? Do a search on character pacing
http://www.picbasic.co.uk/forum/showthread.php?p=3633

[iugmoh]

oky I have these things :
1- max232 converter
2- 4MHZ or 8MHZ crystal
3- PIC16F877A or PIC18f452 or PIC4220

I make a programm and put the values accoding to formula baud=fosc/(16(x+1)) or baud=fosc(64/(x+1))

but the data I recived from pic at pc is a strange data not know

[Archangel]

oky I have these things :
1- max232 converter
2- 4MHZ or 8MHZ crystal
3- PIC16F877A or PIC18f452 or PIC4220

I make a programm and put the values accoding to formula baud=fosc/(16(x+1)) or baud=fosc(64/(x+1))

but the data I recived from pic at pc is a strange data not know

"4MHZ or 8MHZ crystal" 4mhz too slow 8mhz probably too slow
go get this from mister e http://www.mister-e.org/pages/picmulticalcpag.html
using Mister_e's calculator set for 8mhz we get these settings:

RCSTA = $90 ' Enable serial port & continuous receive
TXSTA = $24 ' Enable transmit, BRGH = 1
SPBRG = 16 ' 115200 Baud @ 8MHz, 2.12%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

You may need to slow the character pacing a bit. DEFINE CHAR_PACING 1000

[BrianT]

By default, PIC ports have their OFF or IDLE condition as zero volts. RS-232 however defines the IDLE or steady mark to be negative volts at the 25 pin connector. This means the idle condition between the PIC and the MAX232 chip must be HIGH or positive - the reverse of what you might first think.

An asynchronous character begins when the receiving device detects the transition from the steady MARK to a SPACE bit. BUT, if you did nothing to the Txoutput pin before that character started, then the line had been in the space condition for some time. i.e. the start bit goes missing and so the character is corrupted.

Try this.

HIGH Txpin 'sets the RS-232 connector pin to negative = Mark = Idle
pause 1 ' lest the line settle and the remote device see the mark condition
Serout/hserout/serout21 pin, rate, data 'the message now starts with a guaranteed start bit.

HTH
BrianT

[iugmoh]

SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

Oky with PIC16f877a this give me an error because theses registers are not exist

[skimask]

Oky with PIC16f877a this give me an error because theses registers are not exist

And a quick look at the '877A datasheet, Table 10-3, would tell you that getting 115,200 baud out of 4 or 8 Mhz isn't going to happen, unless you can somehow magically get a divisor of 1.5 stuff into that byte value.
You need more crystals in your toolbox.
Actually, what you need is more variety...

[skimask]

I can communicate at 9600 with higher than this the data is not true it's corrupted

2- 4MHZ or 8MHZ crystal
3- PIC16F877A or PIC18f452 or PIC4220

Says right in the back of the manual that a faster clock speed than 4Mhz will most likely be needed with a 4Mhz crystal, like quite a bit faster.
If you're using a '452, turn on the 4xPLL and use the 8Mhz crystal. That'll give you 32Mhz to play with.

[precision]

But i always use 115200 Baud in nokia 3350 sms zone alarm with this code.

DEFINE OSC 12 ( I use 11.0592 mhz xtal after define osc 12 )

OUTPUT PORTC.6 '-- SERIAL Port TX
INPUT PORTC.7 '-- SERIAL Port RX

DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_SPBRG 5 ' 115200 Bauds with 0% error

HSEROUT [X,Y,Z]

[skimask]

But i always use 115200 Baud in nokia 3350 sms zone alarm with this code.

Well, that'll work too, because you're using the HARDWARE USART.
The note at the back of the book is for SERIN(2)/SEROUT(2).
The O/P didn't specify if hardware or software serial was being used...