RS232 & SIOW

almhuq · Joined: 14 Jan 2005 Posts: 4

I'm trying to run an example CCS program. The program is using the RS-232 port. While entering the values 1+2 in the Serial Monitor Input/Output Windows (SIOW) , I don't receive any data from RS232 port and onto my pc, I can only transmit data stream but can't receive over RS232 port.
Here is the example program

#include <18F4520.h>
#fuses HS,NOLVP,NOWDT
#use delay(clock=20000000)
#use rs232 (baud=9600,xmit=PIN_C6,rcv=PIN_C7, stream=RS232)

#include <stdlib.h>
#include <input.c>

void main (){
long a,b,result;

char opr;

setup_timer_0(RTCC_INTERNAL);

while(TRUE){
delay_ms(100);
printf("\r\nEnter the first number: ");
a=get_long();

do {
printf ("\r\nEnter the operator (+-*/): ");
opr=getc();
}while(!isamoung(opr,"+-*/"));

printf("\r\nEnter the second number:");
b=get_long();

switch (opr){
case '+' :result=a+b; break;
case '-' :result=a-b; break;
case '*' :result=a*b; break;
case '/' :result=a/b; break;
}

printf("\r\nThe the result is %lu ",result);
}
}

Guest_7068 · Guest

I did not quite understand. If you are not receiving any data from the PIC, I am guessing you are not able to see the first printf statement ?
Make sure you are using the correct terminal and the baud rates on the PC match that on the PIC.
If you are not able to send data to the PIC, then place your cursor over the 'View Ascii' window and click on it.
Then you can start sending data from the PC to the PIC by simply typing in in.

Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

You set up a stream statement STREAM=RS232 but didn't use it in any I/O (printf getc )
Why? Look into it for it might be your issue.

Guest · Posted: Sun Feb 24, 2008 10:30 am

Guest · Posted: Sun Feb 24, 2008 10:33 am

almhuq · Joined: 14 Jan 2005 Posts: 4

All the port settings are correct (Baud =9600,Parity= None, Data bits= 8, Stop Bits= 1,Flow Control =None) , but still can't see anything on the PC SIOW terminal window. Any ideas guys ?

Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

Things you will probably need.
1) A level converter Ex MAX232
2) A cable wired so that the tx of the PIC passes through the MAX232 pins and onto the rx pin of the PC. Likewise for the tx pin.
3) A common ground wire between the PC and the MAX232 and the PIC.
4) The com port in SIOW must be the comport the cable is attached to.
5) The baud rate parity etc setting in SIOW to be the same as the PIC.

The fact that it works at least in one direction gives courage to assuming that you have most of the above. The cable or connections to MAX 232 pins for the direction that is not working would be a good place to start checking at least twice.

almhuq · Joined: 14 Jan 2005 Posts: 4

ECACE · Joined: 24 Jul 2006 Posts: 94

Try with something really simple first:

Guest · Posted: Tue Feb 26, 2008 3:04 pm

ECACE · Joined: 24 Jul 2006 Posts: 94

In the sample I gave you, you should just be seeing data coming out of pin C7 every second. If you see the data there and on the input pin of the RS232 chip, but don't see if going out, then you may be correct...bad RS232 chip.

Only other thought:

Could it be a null vs non-null modem cable?

Could it just be a bad cable?
I recently had one go bad where either the TX or RX line was intermittently shorting to groud. That was a hair puller!

Do you have two serial ports on your computer?

Any chance there is something wrong with that port?

Or is there any device you have that you can put in place of the demo board that can send data you can recieve? If so you could single out the board from the rest of the setup.
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