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RS232 and RS485 working together ?

 
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Cookie
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RS232 and RS485 working together ?
PostPosted: Tue Mar 20, 2007 6:16 am     Reply with quote
Hello everybody.

I am using PIC 18F2455 as a master to communicate with numerous 16F690.
My first step is to configure the 18F and try sending some data on RS485 line

il watch with an oscilloscoppe , see that data are transmited.

I activate the RS232 , that i connected to a PC for debugging, The PC receive the RS232 data , and print them well on my Screen.

But RS485 do not work any more. Is there something in the hardware of software that avoid them to work together, or i did something wrong ?

I use the RS485.c
with the default Pins
Code:

#if(RS485_USE_EXT_INT == FALSE)
   #ifndef RS485_RX_PIN
   #define RS485_RX_PIN       PIN_C7   // Data receive pin
   #endif

   #ifndef RS485_TX_PIN
   #define RS485_TX_PIN       PIN_C6   // Data transmit pin
   #endif

   #ifndef RS485_ENABLE_PIN
   #define RS485_ENABLE_PIN   PIN_B4   // Controls DE pin.  RX low, TX high.
   #endif

   #ifndef RS485_RX_ENABLE
   #define RS485_RX_ENABLE    PIN_B5   // Controls RE pin.  Should keep low.
   #endif

   #use rs232(baud=9600, xmit=RS485_TX_PIN, rcv=RS485_RX_PIN, enable=RS485_ENABLE_PIN, bits=9, long_data, errors, stream=RS485)
   #use rs232(baud=9600, xmit=RS485_TX_PIN, rcv=RS485_RX_PIN, enable=RS485_ENABLE_PIN, bits=9, long_data, force_sw, multi_master, errors, stream=RS485_CD)


and i activate RS232 like this
Code:


   #if defined(_DEBUG_RS232)
      #use rs232(baud=9600,parity=N, xmit=PIN_B1, rcv=PIN_B0, bits=8,stream=DEBUG)
   #endif
   
   #define RS485_ID  1                 // The device's RS485 address or ID
   #define RS485_USE_EXT_INT FALSE        // Select between external interrupt
   #define RS485_RX_PIN       PIN_C7   // Data receive pin
   #define RS485_TX_PIN       PIN_C6   // Data transmit pin

   #include "RS485.c"


As you can see i uses differents pins for RS232 and RS485
Any advice ?
thanks
Cookie
Guest
PostPosted: Wed Mar 21, 2007 3:29 am     Reply with quote
any help ?

Only thing i need is to know, if i could work , or it cannot. SO i can avoid loosing time trying to make something work that is impossible!


Thanks
Humberto



Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata

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PostPosted: Wed Mar 21, 2007 5:15 am     Reply with quote
Well, you show us only the header pin definitions, but we didnīt see your code.
As long as I understand, your architecture is:
1 Master that comunicate with n Slaves through RS485 and the same Master comunicate
with a PC through RS232, is this ok? If this is the case, of course it should work, the Master
is who handle the whole communications timmings.

Just a comment with your code:
Code:

#ifndef RS485_ENABLE_PIN
   #define RS485_ENABLE_PIN   PIN_B4   // Controls DE pin.  RX low, TX high.
   #endif

   #ifndef RS485_RX_ENABLE
   #define RS485_RX_ENABLE    PIN_B5   // Controls RE pin.  Should keep low.
   #endif

There is a risk of bus contention and is code dependant. Usually I keep tied together PIN2
and PIN3 of the RS485 transceiver (unless you use Full Duplex) and control both pins with
a single PIC output.


Humberto
Cookie
Guest
PostPosted: Wed Mar 21, 2007 8:35 am     Reply with quote
thank you for your anwer.
I make it work, you have to include the RS485.c file BEFORE declare use of rs232. If i do the other way it do not work.

strange ...

thanks for your concern Humberto.
Guest
PostPosted: Sat Apr 21, 2007 4:12 am     Reply with quote
whats your compiler version Cookie
funmix



Joined: 27 Mar 2007
Posts: 33

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PostPosted: Sun Apr 22, 2007 8:55 pm     Reply with quote
HI cookie,

do you mind to share your working code?
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