strange RS232 problem

[newby]

Hello !

...i am trying my first RS232 project and having strange troubles.

I use the hardware uart of a 18F452 for receiving at 4800 baud data from another pic (18F1320) which is sending the data. Both running with each a 8 MHz crystal resonator. I use the same RS232 settings (9 Bits, no parity, same baud rate(4800), hw pins) on both chips.

The problem is, that if i send more than one char, the receiver (18F452) is receiving only garbage after the 1st char.
If i send a string char by char with delays, the string is being received correctly.

I have tried different baud rates, with MAX2323 and with out, i also tried sending the data directly from my laptop which lead to the same result.
I tested "khbit" and also the interrupt method to look for a new char, but it doesn�t change anything.

I think it looks like a timing problem, but what is wrong ?!? My main progam does nothing than waiting for the data (or sending it). Therefore i guess the data baud rates are incorrect - but what could i do ? I also tried to use the BRGH1OK optin in the #use RS232 but i didnt help ?!?

Thank�s for any help...

[asmallri]

The laptop will not know what do do with 9 bits unless the 9th bit is a 1 (space aka idle). Try repeating your tests after selecting 8 bits.

[newby]

Ok, i have set the #use RS232 bits to 8 and now i am able to receive the data from laptop correctly, but it still doesn�t work from PIC to PIC (i have changed the bit# on both pics to 8 ).

Is it a mistake, if i only connect the according transmit pin (18F1320 is sending data) with the receive pin (18F452 should receive data) without connecting the transmit pin from the 18F452 with the receiver pin from the 18F1320 ? I didn�t do it because i only use one direction...

Thank�s for your great help !

[asmallri]

A single transmit and receive is ok. Did you mean the Laptop now RECEIVES data from the PIC?

How about posting some code so I can have a look.

[Guest]

I don�t use one pin for receiving and sending, but i only connected the receive PIN from the 18F452 (receiver) with the transmit PIN from the transmitter 18F1320 - the other way (from 18F452 to 18F1320) is disconnected.

i am able to send data FROM the laptop to the 18F452 without problems now, but still not from 18F1320 to 18F452.

..here comes the code (i reduced the code to the real problem, data is only dummy...)

18F1320: should provide GPS test data and send it to the 18F452

#zero_ram

int32 dummy_counter;
int8 time;

void main() {
disable_interrupts(global);
setup_wdt(WDT_OFF);
port_b_pullups(TRUE);

while (TRUE) {
dummy_counter++;
if (dummy_counter == 450000) {
time++;

#use rs232(baud=4800, parity=N, xmit=PIN_B1, rcv=PIN_B4, bits=8)
printf("$GPRMC,%u,A,B,N,9.3,E,a,,q,0.4,E,A*19", time);
dummy_counter = 0;
}
}
}

***********************************************
18F452: should receive GPS data and temp "store" it for further operation

#ZERO_RAM
#define max_char_anz 40

int1 new_char;
int8 char_counter;
char GPS_data[max_char_anz], char_dummy;

#use rs232(baud=4800, parity=N, xmit=PIN_C6, rcv=PIN_C7, bits=8, stream = GPS)

#int_RDA
RDA_isr() {
new_char = 1;
char_dummy = fgetc(GPS);
}

void main() {
port_b_pullups(TRUE);
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL);

enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);

while (TRUE) {

if (new_char) {
new_char = 0;

if (char_counter < max_char_anz) {
GPS_data[char_counter] = char_dummy;
} else {
char_counter = 0;
GPS_data[char_counter] = char_dummy;
}
char_counter++;
}
}
}

[asmallri]

Could you send the fuse lines. Note that the 32 bit integer 'dummy_counter' is not initialised (maybe CCS sets non initialised variables to zero - i don't know) however, if not then the first iteration of the loop could take a very long time.

[SherpaDoug]

[drh]

In you RDA interrupt routine try:

new_char = 1;
char_dummy = RCREG;
_________________
David

[newby]

The "dummy_counter" var is only to send a "GPS sentence" about every second, nothing more, this code shoes only the part which is malfunctioning...

the #fuses comes direct from the "project -> PIC WIZARD"

transmitter:

#include <18F1320.h>
#use delay(clock=8000000)
#fuses NOWDT, H4, NOFCMEN, NOBROWNOUT, PUT, NOCPD, STVREN, NODEBUG, NOLVP, WRT, NOWRTD, WRTC, IESO, NOEBTR, NOEBTRB, NOMCLR, PROTECT, CPB, WRTB

receiver:

#include <18F452.h>
#device ICD=TRUE
#use delay(clock=8000000)
#fuses NOWDT,WDT128,HS, NOPROTECT, NOOSCSEN, NOBROWNOUT, BORV20, PUT, STVREN, DEBUG, NOLVP, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, NOCPB, NOEBTR, NOEBTRB

@drh: RCREG doesn�t function -> unkown identifier...

Thanks a lot for your assistance !

[drh]

Sorry about that.

#BYTE RCREG = 0x0FAE


One of the first things I do when using a new processor is create a xxx.def file. I #include this near the beginning of my source file. This file contains all the special function register addresses and bit definitions.
_________________
David

[asmallri]

[Guest]

...the problem was, that i have used the PLLx4 mode in combination with an ceramic resonator as oscillator. After i have swichted off the PLLx4, it worked....

[censored] happens ... thanks a lot for your help !