Rs485 Using Hserin/hserout

[koossa]

Good day

I have a simple setup with <b>2 x PIC 16F877</b> and want to do <b>RS485 Comms</b> using <b>2 x SN75176</b> chips.
The one PIC is the <b>Master</b> and the other the <b>Slave</b>.

For debug purposes I send messages to my <b>PC using RS232</b> from the Master.


<font color="#993300">Below is my code for the MASTER:</font>
<hr>
<code>
&nbsp;&nbsp;Include "Modedefs.bas"
&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;DEFINE&nbsp;&nbsp;&nbsp;&nbsp; OSC 4

&nbsp;&nbsp;DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;VAR PORTC.5&nbsp;&nbsp;&nbsp;&nbsp; ' DE and RE Pin of SN75176
&nbsp;&nbsp;RS232_DEBUG_PIN VAR PORTB.5&nbsp;&nbsp;&nbsp;&nbsp; ' Debugging to PC
&nbsp;&nbsp;LEDPIN&nbsp;&nbsp;&nbsp;&nbsp; VAR PORTD.2&nbsp;&nbsp;&nbsp;&nbsp; ' LED to confirm PIC is running
&nbsp;&nbsp;DATARECEIVED&nbsp;&nbsp;VAR BYTE

&nbsp;&nbsp;'======== HSEROUT, HSERIN SETTINGS ==========&nbsp;&nbsp;
&nbsp;&nbsp;DEFINE HSER_RCSTA 90h
&nbsp;&nbsp;define HSER_TXSTA 20h
&nbsp;&nbsp;define HSER_SPBRG 103
&nbsp;&nbsp;DEFINE HSER_CLOERR 1
&nbsp;&nbsp;RCIF&nbsp;&nbsp;&nbsp;&nbsp;VAR PIR1.5
&nbsp;&nbsp;TXIF&nbsp;&nbsp;&nbsp;&nbsp;VAR PIR1.4
&nbsp;&nbsp;
&nbsp;&nbsp;ADCON1 = 7
&nbsp;&nbsp;TRISC = %10000000
&nbsp;&nbsp;
Main:
&nbsp;&nbsp;HIGH LEDPIN&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs p;&nbsp;&nbsp; ' Indicate PIC is running
&nbsp;&nbsp;HIGH DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp; ' Make ready for TX
&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;HSEROUT ["S0"]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ' Send "S0"
&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;LOW LEDPIN
&nbsp;&nbsp;LOW DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;' Make ready for RX
&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;SEROUT RS232_DEBUG_PIN,N2400,["WAITING FOR REPLY..", 13, 10] ' DEBUG TO PC
&nbsp;&nbsp;if RCIF then
&nbsp;&nbsp;&nbsp;&nbsp;hserin 100,Main,[WAIT ("R"),DATARECEIVED]
&nbsp;&nbsp;&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;ENDIF
&nbsp;&nbsp;SEROUT RS232_DEBUG_PIN,N2400,["REC:",DATARECEIVED, 13, 10] ' DEBUG TO PC
&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;
GOTO Main

END
</code>
<hr>

<font color="#993300">Here is the code for the SLAVE:</font>
<hr>
Include "Modedefs.bas"

DEFINE&nbsp;&nbsp;&nbsp;&nbsp; OSC 4

&nbsp;&nbsp;DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;VAR PORTC.5&nbsp;&nbsp;&nbsp;&nbsp; ' DE and RE Pin of SN75176
&nbsp;&nbsp;LEDPIN&nbsp;&nbsp;&nbsp;&nbsp; VAR PORTD.2&nbsp;&nbsp;&nbsp;&nbsp; ' LED to confirm PIC is running
&nbsp;&nbsp;DATARECEIVED&nbsp;&nbsp;VAR BYTE
&nbsp;&nbsp;
&nbsp;&nbsp;'======== HSEROUT, HSERIN SETTINGS ==========
&nbsp;&nbsp;DEFINE HSER_RCSTA 90h
&nbsp;&nbsp;define HSER_TXSTA 20h
&nbsp;&nbsp;define HSER_SPBRG 103
&nbsp;&nbsp;DEFINE HSER_CLOERR 1
&nbsp;&nbsp;RCIF&nbsp;&nbsp;&nbsp;&nbsp;VAR PIR1.5
&nbsp;&nbsp;TXIF&nbsp;&nbsp;&nbsp;&nbsp;VAR PIR1.4

&nbsp;&nbsp;ADCON1 = 7
&nbsp;&nbsp;TRISC = %10000000
&nbsp;&nbsp;
Main:

&nbsp;&nbsp;HIGH LEDPIN&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs p;&nbsp;&nbsp; ' Indicate PIC is running
&nbsp;&nbsp;LOW DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;' Make ready for RX
&nbsp;&nbsp;PAUSE 100&nbsp;&nbsp;
&nbsp;&nbsp;if RCIF then
&nbsp;&nbsp;&nbsp;&nbsp;hserin 100,Main,[WAIT ("S"),DATARECEIVED] ' Looking for "S0"
&nbsp;&nbsp;&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;&nbsp;&nbsp;IF DATARECEIVED = "0" THEN
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HIGH DE_OR_RE&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ' Make ready for RX
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PAUSE 100
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HSEROUT ["R1"]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n bsp;&nbsp;&nbsp;&nbsp; ' Send R1
&nbsp;&nbsp;&nbsp;&nbsp;ENDIF
&nbsp;&nbsp;endif
&nbsp;&nbsp;LOW LEDPIN
&nbsp;&nbsp;PAUSE 100
GOTO MAIN

END
<hr>


<font color="#993300">Please find attached my schematic!</font>

<hr>
MY QUESTION:
<hr>
<font color="#993300">
The first time I connected the Slave to the 5v power and then after about 5 seconds the Master I get the following on the PC Side:
</font>
<b>
WAITING FOR REPLY..
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
REC:ÿ
</b>

<font color="#993300">
Then when I done it again I get the following:
</font>
<b>
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
</b>

<font color="#993300">
When I startup the Master first and then after a few seconds the Slave I get the following
</font>
<b>
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
REC:ÿ
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
</b>

<font color="#993300">
When I connect the Slave first, then the Master and then after a few seconds disconnect and connect the master again, it just keep on returning <b>"WAITING FOR REPLY.."</b>
</font>
<b>
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
REC:1
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
WAITING FOR REPLY..
</b>


<font color="#993300">
It is very unreliable, sometimes it is working and sometimes not.

Am I doing something stupid???
</font>


Thank you
Koossa