My first DT_INT code has a problem..... [Archive]

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

'DEVICE 16F882

@ __config _CONFIG1, _HS_OSC & _WDT_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF

DEFINE OSC 16
DEFINE LCD_EREG PORTC ' SET ENABLE PORT
DEFINE LCD_EBIT 3 ' SET ENABLE BIT

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

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

INCLUDE "DT_INTS-14.bas" ; Base Interrupt System
INCLUDE "ReEnterPBP.bas" ; Include if using PBP interrupts

ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
INT_Handler RX_INT, _ISR, PBP, yes
endm
INT_CREATE ; Creates the interrupt processor
ENDASM

@ INT_ENABLE RX_INT ; enable EUSART (INT) interrupts

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

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

OERR VAR RCSTA.1 ' Alias USART over-run bit
CREN VAR RCSTA.4 ' Alias USART continuous receive enable bit
RCIF VAR PIR1.5 ' Alias USART received character interrupt flag bit

BytesIn VAR BYTE[16]
ByteCnt VAR BYTE
Got VAR BYTE
Problem VAR BYTE
Prob_Cnt VAR BYTE
Stx VAR BYTE
String VAR BYTE
SW1 VAR PORTB.0
SW2 VAR PORTB.1
Reps VAR WORD

'************************************************* **********************

MAIN:

PAUSE 1000 ' LCD start-up delay
CLEAR

LCDOUT $FE,1
LCDOUT $FE,$80," PLEASE "
LCDOUT $FE,$C0," WAIT "
PAUSE 500

LCDOUT $FE,$80," " ' CLEARS SCREEN BETTER THAN $FE,1
LCDOUT $FE,$C0," "
Problem=0

IF !OERR THEN LOOP ' If OERR=0 no over-run condition's present
CREN = 0 ' Disable receive
CREN = 1 ' Re-enable & clear OERR "over-run" flag
GOTO MAIN ' start over, including the count

LOOP:

@ USART_Init 9600 ' SET BAUDRATE
Stx=($01) ' SET START OF TEXT CHARACTOR
String=8 ' SET LENGTH OF SERIAL STRING
Prob_Cnt=56 ' SET # OF BYTES TO TRIGGER "SETUP PROBLEM" DISPLAY

LCDOUT $FE,$80,32 ' ^^^^^^BREAKS IF REMMED OUT (GARBAGE DATA)^^^^^^^^

IF Got=1 THEN
GOSUB Show_Routine_One
ENDIF

IF Problem=>Prob_Cnt THEN
GOSUB Prob_Disp
ENDIF

GOTO LOOP

Show_Routine_One: ' DISPLAY DATA
LCDOUT $FE,$80,32,32,BytesIn(1),BytesIn(2),BytesIn(4),Byt esIn(5),BytesIn(7),32
LCDOUT $FE,$C0," " ' BLANK SECOND ROW ON LCD
ByteCnt=0
Got=0
Problem=0
RETURN

Prob_Disp:
LCDOUT $FE,$80,32,"SETUP",32,32
LCDOUT $FE,$C0,"PROBLEM"
Problem=0
RETURN

No_Data:
LCDOUT $FE,$80,32,32,32,"NO",32,32,32
LCDOUT $FE,$C0,32,32,"DATA",32
Reps=0
RETURN

'======================== INTERRUPT SERVICE ROUTINE===========================
ISR:

IF RCIF THEN ' If RCIF=1 there's a new character in RCREG
BytesIn[ByteCnt]=RCREG ' Yes. Then store it in array
ByteCnt=ByteCnt+1 ' Increment array index pointer

ENDIF
IF BytesIn<>Stx THEN
ByteCnt=0
Problem=Problem+1
ENDIF

IF ByteCnt=>String THEN
Got=1 'INDICATE THAT THIS IS A NEW PACKET

ENDIF

'************************************************* **************************
@ INT_RETURN
'************************************************* *************************

mister_e

- 11th April 2009, 16:48

I would think it's because you set the baudrate within this loop, and it need some time for the USART to initialize/settle. Usually, you want to set the USART at the top and only once. So my guess is to move the @ USART_Init 9600 line before the main.

You could still place the following lines at the top of your code (with all other register init), and forget @ USART_Init

RCSTA = $90 ' Enable serial port & continuous receive
TXSTA = $20 ' Enable transmit, BRGH = 0
SPBRG = 25 ' 9600 Baud @ 16MHz, 0.16%

E Kizer

- 13th April 2009, 13:37

Thanks Steve,

I'll look into that.