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(SOLVED) Problem reading data from RS232

 
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JeffLewcock



Joined: 10 Apr 2007
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(SOLVED) Problem reading data from RS232
PostPosted: Mon Jan 28, 2013 9:33 am     Reply with quote

I am trying to program a device to control a clock using GPS input for time.
I am having a problem getting data from the 232 I have read all the posts regarding this but cannot get even the simplest code to work.
I am reading the input on rs232 stream "GPS" and trying to transfer it to stream "PC"
I am currently using the EX_SISR.c code as a basis but this does not work.
All I get on the "PC" is

Running...

Buffered data =>
Buffered data =>

I notice that i do not get "interrupted" variable printed whether 0 or 1

Have I missed something or done something stupid ?

Nixie_Clock.h
Code:

#include <18F67J60.h>
#device adc=16
#FUSES NOWDT                    //No Watch Dog Timer
#FUSES WDT128                   //Watch Dog Timer uses 1:128 Postscale
#FUSES NOXINST                  //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOETHLED                 //Ethernet LED disabled
#use delay(clock=25000000)
#use rs232(baud=4800,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=GPS,errors)
#use rs232(baud=4800,parity=N,xmit=PIN_A2,rcv=PIN_A3,bits=8,stream=PC)
#define LED PIN_B4


Nixie_clock.c
Code:




Last edited by JeffLewcock on Tue Jan 29, 2013 5:09 am; edited 2 times in total
Gabriel



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PostPosted: Mon Jan 28, 2013 9:56 am     Reply with quote

.... If you post CCS Examples, You are going to have a bad time.

Read the forum rules...
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CCS PCM 5.078 & CCS PCH 5.093
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Mon Jan 28, 2013 10:08 am     Reply with quote

The obvious thing is how your RS232 transceivers are wired?.
You do realise that RS232 is a signalling standard, and the PIC cannot generate this standard?. It _requires_ a transceiver chip to generate this....

Best Wishes
JeffLewcock



Joined: 10 Apr 2007
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PostPosted: Mon Jan 28, 2013 10:15 am     Reply with quote

Sorry Example code removed !!!
Brain not in gear.

I have transmitted data from both streams to the PC terminal both streams have level shifting hardware.

I have changed the example EX.SISR.c to use streams (I think).

In the isr
Code:
buffer[next_in]=fgetc(GPS);

and added a flag "interuppted" that gets set to 1 if the isr fires.

In the main i have added
Code:
fprintf(PC,interrupted);

and changed
printf("\r\n\Running...\r\n"); to fprintf(PC,"\r\nBuffered data => ");

and

putc( bgetc() ); to fputc(bgetc(),PC );

Jeff
ezflyr



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PostPosted: Mon Jan 28, 2013 10:47 am     Reply with quote

Hi,

In addition to software issues, you may have hardware issues as well! What GPS are you connecting to the PIC? Can you post a link? Can you describe how you have it connected? Before I dug into *any* software at all, I'd want to be sure that my hardware is correct, or you'll waste a lot of time!

John
Ttelmah



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PostPosted: Mon Jan 28, 2013 11:41 am     Reply with quote

JeffLewcock wrote:
Sorry Example code removed !!!
Brain not in gear.


I have transmitted data from both streams to the PC terminal both. streams have level shifting hardware.

I have changed the example EX.SISR.c to use streams (I think).

In the isr
buffer[next_in]=fgetc(GPS);
and added a flag "interuppted" that gets set to 1 if the isr fires.


in the main i have added
fprintf(PC,interrupted);

and changed
printf("\r\n\Running...\r\n"); to fprintf(PC,"\r\nBuffered data => ");

and

putc( bgetc() ); to fputc(bgetc(),PC );

Jeff


bkbhit already tells you a character has been received. You don't need your 'interrupted' flag.

Code:

if (bkbhit()) {
   fputc(bgetc(),PC);
}


Best Wishes
JeffLewcock



Joined: 10 Apr 2007
Posts: 29

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PostPosted: Mon Jan 28, 2013 12:42 pm     Reply with quote

Hi Ttelmah

Thanks for your input, I did realise this but could not work out whether somehow kbhit was being ignored so added the "interrupted" flag as a double check.

The weird thing is that the value of "interrupted" is never sent to the "PC" whatever the value whereas "Buffered data" is.

I will check the hardware again tomorrow as this seems the most likely explanation.

Thanks again

Jeff
ckielstra



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PostPosted: Mon Jan 28, 2013 5:12 pm     Reply with quote

... and as always: post your compiler version number!
JeffLewcock



Joined: 10 Apr 2007
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PostPosted: Tue Jan 29, 2013 5:11 am     Reply with quote

Thanks Guys !

I have solved the problem, one of the cables I was using crossed pins 2 and 3 on the DB9

Feel a bit silly now ! Embarassed

jeff
temtronic



Joined: 01 Jul 2010
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PostPosted: Tue Jan 29, 2013 6:22 am     Reply with quote

Hay Jeff don't feel silly.

Why 'they' changed the legacy standards when 9 pin connectors came out is beyond me and yes, I get 'confused' once in awhile as I use both 25 and 9 pin RS-232 sonncetors all the time.

sigh..so much for 'standards'!

jay
ezflyr



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PostPosted: Tue Jan 29, 2013 7:27 am     Reply with quote

Hi,

The important 'take-away' for you, and anyone else reading this thread, is that's essential to make sure your hardware is working correctly before you actually begin coding in earnest! Anytime I start a new project, the first thing I do is write a collection of simple routines to test the hardware. This strategy always saves a lot of grief down the road!

John
bkamen



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PostPosted: Tue Jan 29, 2013 8:23 am     Reply with quote

If pins 2/3 were swapped, did the cable have female connectors at both ends?

If so, this was probably a Null modem cable. (Unless it was homemade in which it could have been a wiring discrepancy.)


If the cable was male->female, then it is probably a wiring error. (if professionally made)

It would be a good exercise to find out the information surrounding the cable for next time... but at least your project is working now.
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