My first DT_INT code has a problem.....

**E Kizer** · - 11th April 2009, 15:37

This is my first attempt at using a USART with DT's INT's and I ran into a problem that I can't figure out. I was using my LCD for debugging and everything was working fine until I remmed out the LCDOUT line. Now it turns the received characters into garbage. If I put back the LCDOUT line the received characters are fine.
Can anyone explain to me why it does this, I must be doing something fundamentally wrong.
Thanks,
Ed Kizer

Code:

<font color="#000080"><i>'DEVICE 16F882

</i></font><font color="#008000">@ __config _CONFIG1, _HS_OSC &amp; _WDT_ON &amp; _MCLRE_ON &amp; _LVP_OFF &amp; _CP_OFF
                                    
</font><b>DEFINE </b>OSC 16
<b>DEFINE </b>LCD_EREG PORTC <font color="#000080"><i>' SET ENABLE PORT
</i></font><b>DEFINE </b>LCD_EBIT 3 <font color="#000080"><i>' SET ENABLE BIT

</i></font>OPTION_REG.7=0      <font color="#000080"><i>' TURN ON PORTB WEAK PULL-UPS
</i></font>ANSELH=0       <font color="#000080"><i>'  DISABLE PORT B ANALOG, ENABLE DIGITAL I/O
</i></font>CM1CON0=0     <font color="#000080"><i>' TURN OFF COMPARATORS PORTA(1)
</i></font>CM2CON0=0        <font color="#000080"><i>' TURN OFF COMPARTORS PORTB(2)
</i></font>VRCON=0          <font color="#000080"><i>' A/D Voltage reference disabled
</i></font>ANSEL=0           <font color="#000080"><i>' TURN OFF PORT A A/D, ENABLE DIGITAL I/O
</i></font>TRISA=0 <font color="#000080"><i>'set portA to OUTPUTS
</i></font>TRISB=$FF <font color="#000080"><i>' set port b TO ALL INPUTS  %11111111
</i></font>TRISC=$80  <font color="#000080"><i>' SET PORT C BIT 7 TO INPUT  %10000000


'***********INSTANT INTERRUPT ROUTINES BY DARRYL TAYLOR************
 '******************* USE MPASM TO ASSEMBLE **************



</i></font><b>INCLUDE </b><font color="#FF0000">&quot;DT_INTS-14.bas&quot;     </font><font color="#000080"><i>; Base Interrupt System
</i></font><b>INCLUDE </b><font color="#FF0000">&quot;ReEnterPBP.bas&quot;     </font><font color="#000080"><i>; Include if using PBP interrupts

</i></font><b>ASM
</b><font color="#008000">INT_LIST  macro    </font><font color="#000080"><i>; IntSource,   Label,  Type, ResetFlag?
        </i></font><font color="#008000">INT_Handler    RX_INT,  _ISR,   PBP,  yes
    endm
    INT_CREATE               </font><font color="#000080"><i>; Creates the interrupt processor
</i></font><b>ENDASM

</b><font color="#008000">@   INT_ENABLE   RX_INT     </font><font color="#000080"><i>; enable EUSART (INT) interrupts


'***********************************************************************
'*************** DT's BAUD SETUP ROUTINE *************************

</i></font><b>ASM
</b><font color="#008000">USART_Init  macro  Baud
    CHK?RP  TXSTA
    clrf    TXSTA
_SPBRG = (OSC * 1000000) / 16 / Baud - 1     </font><font color="#000080"><i>; calc SPBRG @ High baud rate
    </i></font><font color="#008000">if _SPBRG &gt; 255                          </font><font color="#000080"><i>; if SPBRG is too high
</i></font><font color="#008000">_SPBRG = (OSC * 1000000) / 64 / Baud - 1     </font><font color="#000080"><i>; calc for Low baud rate
        </i></font><font color="#008000">bcf   TXSTA, BRGH                    </font><font color="#000080"><i>; Set BRGH to Low Speed
        </i></font><font color="#008000">if _SPBRG &gt; 255
_SPBRG = 255
        endif
    else                                     
        bsf   TXSTA, BRGH                    </font><font color="#000080"><i>; Set BRGH to High Speed
    </i></font><font color="#008000">endif
    bsf     TXSTA, TXEN                      </font><font color="#000080"><i>; Set Transmit Enable bit
    </i></font><font color="#008000">movlw   _SPBRG          
    CHK?RP  SPBRG
    movwf   SPBRG                            </font><font color="#000080"><i>; load the calulated SPBRG
    </i></font><font color="#008000">movlw   B'10010000'                      </font><font color="#000080"><i>; enable USART
    </i></font><font color="#008000">CHK?RP  RCSTA
    movwf   RCSTA
    endm
</font><b>ENDASM
</b><font color="#000080"><i>'****************************************************************************

 
</i></font>OERR <b>VAR </b>RCSTA.1 <font color="#000080"><i>' Alias USART over-run bit
</i></font>CREN <b>VAR </b>RCSTA.4 <font color="#000080"><i>' Alias USART continuous receive enable bit
</i></font>RCIF <b>VAR </b>PIR1.5 <font color="#000080"><i>' Alias USART received character interrupt flag bit

</i></font>BytesIn <b>VAR BYTE</b>[16]
ByteCnt <b>VAR BYTE
</b>Got <b>VAR BYTE
</b>Problem <b>VAR BYTE
</b>Prob_Cnt <b>VAR BYTE
</b>Stx <b>VAR BYTE
</b>String <b>VAR BYTE
</b>SW1 <b>VAR </b>PORTB.0
SW2 <b>VAR </b>PORTB.1
Reps <b>VAR WORD


</b><font color="#000080"><i>'***********************************************************************

</i></font>MAIN:

<b>PAUSE </b>1000 <font color="#000080"><i>' LCD start-up delay
</i></font><b>CLEAR
        
LCDOUT </b>$FE,1
<b>LCDOUT </b>$FE,$80,<font color="#FF0000">&quot; PLEASE &quot;
</font><b>LCDOUT </b>$FE,$C0,<font color="#FF0000">&quot;  WAIT  &quot; 
</font><b>PAUSE </b>500

<b>LCDOUT </b>$FE,$80,<font color="#FF0000">&quot;        &quot;   </font><font color="#000080"><i>' CLEARS SCREEN BETTER THAN $FE,1
</i></font><b>LCDOUT </b>$FE,$C0,<font color="#FF0000">&quot;        &quot;
    </font>Problem=0

<b>IF </b>!OERR <b>THEN </b>LOOP <font color="#000080"><i>' If OERR=0 no over-run condition's present
    </i></font>CREN = 0 <font color="#000080"><i>' Disable receive
    </i></font>CREN = 1 <font color="#000080"><i>' Re-enable &amp; clear OERR &quot;over-run&quot; flag
</i></font><b>GOTO </b>MAIN <font color="#000080"><i>' start over, including the count

</i></font>LOOP:


<font color="#008000">@ USART_Init  9600           ' SET BAUDRATE
    </font>Stx=($01)                <font color="#000080"><i>' SET START OF TEXT CHARACTOR
    </i></font>String=8                 <font color="#000080"><i>' SET LENGTH OF SERIAL STRING
    </i></font>Prob_Cnt=56             <font color="#000080"><i>' SET # OF BYTES TO TRIGGER &quot;SETUP PROBLEM&quot; DISPLAY



                   
</i></font><b>LCDOUT </b>$FE,$80,32       <font color="#FF0000"><i>' ^^^^^^BREAKS IF REMMED OUT (GARBAGE DATA)^^^^^^^^



                    
</i></font><b>IF </b>Got=1 <b>THEN 
GOSUB </b>Show_Routine_One
<b>ENDIF

IF </b>Problem=&gt;Prob_Cnt <b>THEN
GOSUB </b>Prob_Disp
<b>ENDIF


GOTO </b>LOOP
   
Show_Routine_One:           <font color="#000080"><i>' DISPLAY DATA
</i></font><b>LCDOUT </b>$FE,$80,32,32,BytesIn(1),BytesIn(2),BytesIn(4),BytesIn(5),BytesIn(7),32
<b>LCDOUT </b>$FE,$C0,<font color="#FF0000">&quot;       &quot;     </font><font color="#000080"><i>' BLANK SECOND ROW ON LCD
    </i></font>ByteCnt=0
    Got=0
    Problem=0
<b>RETURN    

</b>Prob_Disp:
<b>LCDOUT </b>$FE,$80,32,<font color="#FF0000">&quot;SETUP&quot;</font>,32,32
<b>LCDOUT </b>$FE,$C0,<font color="#FF0000">&quot;PROBLEM&quot;
    </font>Problem=0
<b>RETURN
 
</b>No_Data:
<b>LCDOUT </b>$FE,$80,32,32,32,<font color="#FF0000">&quot;NO&quot;</font>,32,32,32
<b>LCDOUT </b>$FE,$C0,32,32,<font color="#FF0000">&quot;DATA&quot;</font>,32
    Reps=0
<b>RETURN

</b><font color="#000080"><i>'======================== INTERRUPT SERVICE ROUTINE===========================
</i></font>ISR:
     
         
<b>IF </b>RCIF <b>THEN </b><font color="#000080"><i>' If RCIF=1 there's a new character in RCREG
    </i></font>BytesIn[ByteCnt]=RCREG <font color="#000080"><i>' Yes. Then store it in array
    </i></font>ByteCnt=ByteCnt+1 <font color="#000080"><i>' Increment array index pointer    
    
</i></font><b>ENDIF
IF </b>BytesIn&lt;&gt;Stx <b>THEN
    </b>ByteCnt=0
    Problem=Problem+1
<b>ENDIF

IF </b>ByteCnt=&gt;String <b>THEN
     </b>Got=1  <font color="#000080"><i>'INDICATE THAT THIS IS A NEW PACKET                    
   
</i></font><b>ENDIF
    

</b><font color="#000080"><i>'***************************************************************************
</i></font><font color="#008000">@ INT_RETURN
</font><font color="#000080"><i>'**************************************************************************




</i></font>

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