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kikirojas
Joined: 30 Jan 2008
Posts: 4
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| trouble with usart pic16f628A |
 Posted: Fri Jul 25, 2008 1:52 pm |
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I'm working with the pic 628A. I need to work with usart.
I receive data from GPS in rcv=PIN_B1 and transmit this data by
xmit=PIN_B2, to the terminal soft in a PC.
With the next code it works ok:
| Code: | #if defined(__PCM__)
#include <16F628A.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOMCLR,NOBROWNOUT
#use delay(clock=20000000)
#use rs232(baud=4800, xmit=PIN_B2, rcv=PIN_B1,stream=PC)
#endif
#include <stdlib.h>
int c;
void main() {
printf("\r\n\RUNNING\r\n");
while(TRUE){
c = fgetc(PC); //read character from UART
fputc(c,PC); //put character to PC
} |
on the hyperterminal I can see the next and more:
| Code: | \0A
\0ARUNNING\0D
\0A$PSRFTXT,Version:GSW3.2.0PAT_3.1.00.12-SDK001P1.00d
\0D
\0A$PSRFTXT,Version2:F-GPS-03-0607031\0D
\0A$PSRFTXT,WAAS Disable\0D
\0A$PSRFTXT,TOW: 512216\0D
\0A$PSRFTXT,WK: 1488\0D
\0A$PSRFTXT,POS: 2730091 -4488622 -3604509\0D
\0A$PSRFTXT,CLK: 94823\0D
\0A$PSRFTXT,CHNL: 12\0D
\0A$PSRFTXT,Baud rate: 4800 \0D |
It works ok. But when I want to add the line printf("Hola") it does not work ok.
| Code: |
int c;
void main() {
printf("\r\n\RUNNING\r\n");
while(TRUE){
c = fgetc(PC); //read character from UART
fputc(c,PC); //put character to PC
printf("Hola");
}
} |
on the hyperterminal I can see only the next :
| Code: | \0A
\0ARUNNING\0D
$HolaPHolaSHolaRHola |
Why can I see only the four characters $PSR with the four "Hola" between them ?
Which is the problem with printf("Hola") in the loop ?
Thank you in advance. |
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Ttelmah
Guest
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| Posted: Fri Jul 25, 2008 3:10 pm |
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Time.
The modem is sending the characters at 4800bps. The ouput sends characters at 4800bps. When one character arrives, there is only time to send _one_ character out, before another character arrives. There is a small amount of buffering (just under two characters only).
Hence the code starts losing characters.
In your case, the internal hardware buffer overflows after the fourth character is received. Because you don't have the 'ERRORS' keyword in the UART setup, this stops further receiving (hang the UART, with an overrun error). With 'ERRORS', the code will no longer hang, but will simply miss about 2/3rd of the characters.
Now, the GPS, should only send it's data in short bursts, with quite long gaps between them. If you want to send more data than is arriving, you need to buffer the incoming serial data. The EX_SISR interrupt driven serial receive code, will work for this, and provided your reply fits before the next packet of data from the GPS, gives the time needed for the PIC to catch up.
Best Wishes |
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kikirojas
Joined: 30 Jan 2008
Posts: 4
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| usart theory or tutorial |
| Posted: Sat Jul 26, 2008 9:18 am |
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Dear sirs:
I need to build a system with a hardware(xmit=PIN_B2, rcv=PIN_B1) usart and the other software usart. But I have a lot of doubts about the theory about "two usarts" . I would like help about when a how to use "INT_RDA" "INT_TBE" "kbhit" " need I implement a buffer for incoming data in usart by soft ?" " and in usart by hardware ?" "Need I use the INT_EXT for usart by software ?"
My system must be receive in usart by hardware a gps signal ( 4800 bauds ) , and in a usart by software receive a gsm data and transmit data to 19200 bauds.
Is possible to implement this system with a pic 16f628A with a 20 Mhz crystal.
thank you in advance |
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drh
Joined: 12 Jul 2004
Posts: 192
Location: Hemet, California USA
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| Posted: Sat Jul 26, 2008 12:14 pm |
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| Quote: | Which is the problem with printf("Hola") in the loop ?
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Your #use RS232 pre-processor directive is configured to use "streams".
Change the printf("Hola");
to frpintf(PC, "Hola");
_________________
David |
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