Receiving Packet Array In Usart

[skimask]

Send out bytes using serout one byte at a time instead of a whole string of bytes and in between sending out bytes, do a quick serin check to see if anything is there.

[crhomberg]

I don't have a choice, the data always comes in groups of 8.
The serout is just for debugging, not really needed finally.
I must be able to read in 8 bytes and then check if the 1st one is $A0 and the 7th $AF. When that is true I can use the data. The packets come at 4800bps and in bursts relatively far apart (That is how I got away with serin2 until now, it just lost packets from time to time)
I need to stop what the program is doing when that 1st byte arrives and then channel in the next 7 into an array or sepparate vars.

Regards

Chris

[sougata]

Hi,

I have done an application where a PIC 18F452 is connected in parallel with a dumb terminal. It parses incoming strings on the fly in an asm based INT routine and keeps required data in specified variables.For your app @4800 try this.

1. Set up a ring buffer.
2. Within the interrupt hunt for the trailer, if found set a flag.
3. Jump back to the header location to find if it was a complete command set.
4. Verify Checksum
Then you now where your data of interest are and handle them in the main routine.

[skimask]

I don't have a choice, the data always comes in groups of 8. The serout is just for debugging, not really needed finally. I must be able to read in 8 bytes and then check if the 1st one is $A0 and the 7th $AF. When that is true I can use the data. The packets come at 4800bps and in bursts relatively far apart (That is how I got away with serin2 until now, it just lost packets from time to time) I need to stop what the program is doing when that 1st byte arrives and then channel in the next 7 into an array or sepparate vars.
Regards
Chris

Put that input on portB and use the 'interrupt on change' feature...
I.E. - you're transmitting, something starts coming in on the serial line. Stop transmitting immediately and start receiving.

What you're trying to do isn't impossible. It's just getting past the PicBasicPro serial commands and using straight hardware and interrupts to handle it in the 'background'.
I suggest playing around with interrupts first, doesn't matter which one, just play with them. Then work your way up to using the serial port, both RX and TX, use some sort of buffering setup.

[crhomberg]

I don't understand how to setup a ring buffer, is this in the main program?
How does a ring buffer work?
Is this using asm interrupts or ON INT?

[Darrel Taylor]

Chris,

You already have a buffer, it doesn't need to be a "ring".
But it does need to work properly.

In your original routine...

'******************* interrupt routine *********************
disable

myroutine:
if PIR1.5=1 then
    PELCO[BYTECOUNT]=RCREG
    IF RCREG=$AF THEN
        GOSUB SENDATA
        PIR1.5=0
    ELSE
        BYTECOUNT=BYTECOUNT+1
        GOTO MYROUTINE
    ENDIF
ENDIF
        
resume
enable

When testing the value of RCREG, it also removes a byte from the USARTs buffer (if one's available).

And, there's currently no way to reset BYTECOUNT, it just keeps counting, which then overwrites memory areas that you don't want it to.

Try this...

'******************* interrupt routine *********************
disable

myroutine:
if PIR1.5=1 then
    temp = RCREG
    if temp = $A0 then BYTECOUNT = 0
    if BYTECOUNT < 8 then    
        PELCO[BYTECOUNT]=temp
        BYTECOUNT=BYTECOUNT+1
        IF (BYTECOUNT = 8) and (temp=$AF) THEN GOSUB SENDATA
        GOTO MYROUTINE
    ENDIF
ENDIF
        
resume
enable

HTH,

[crhomberg]

Thanks for the example code, I modified it to my variable names and included the main loop but it just gives me vales of 0 for BUFFER, what have I done wrong. I checked if it was interrupting and it is.

Here is my code:

'************************************************* **
@ device hs_OSC, wdt_on, pwrt_on, protect_off
define osc 20
Include "modedefs.bas"
trisc.6=0
TRISC.7=1
TRISA.0=0


RCSTA = %10010000 ' ENABLE USART AND SET TO CONTINUOUS RECEIVE
SPBRG = 64 'SET TO 4800bps
INTCON = %11000000 'ENABLE GLOBAL & PERIFERAL INTERRUPTS
RCIF VAR PIR1.5 'FLAG IS THE INTERRUPT WHEN A BYTE IS IN THE USART BUFFER
RCIE VAR PIE1.5
OERR VAR RCSTA.1
CREN VAR RCSTA.4
test var porta.0
BAUD CON 16390


BUFFER VAR BYTE[8] 'BUFFER FROM USART TO COLLECT THE 8 BYTES
BYTECOUNTER VAR BYTE 'USED TO COUNTER BYTES INTO THE BUFFER
BFULL VAR BIT 'FLAGS THAT THE BUFFER HAS ALL 8 BYTES
VALUE VAR BYTE 'A TEMP SINGLE BYTE RECEIVED FROM THE USART
COUNTER VAR WORD 'USED FOR LOOP IN MAIN PROGRAM


BUFFER = 0
BYTECOUNTER = 0
BFULL = 0
VALUE = 0
RCIE=1 'ENABLE USART RECEIVE INTERRUPT FLAG

ON INTERRUPT GOTO GETDATA

GOTO MAIN:


disable


GETDATA:

if RCIF=1 then 'IF RECEIVE FLAG IS ON

VALUE=RCREG 'READ THE VALUE IN THE USART BUFFER

IF VALUE = $A0 THEN 'CHECK TO SEE IF THE BYTE IS THE START BYTE
BYTECOUNTER=0 'AND SET THE COUNTER TO FIRST BYTE
ENDIF

IF BYTECOUNTER < 8 THEN

BUFFER[BYTECOUNTER] = VALUE

BYTECOUNTER=BYTECOUNTER+1 'INCREMENT FOR NEXT BYTE

IF (BYTECOUNTER = 8) AND (VALUE=$AF) THEN
TOGGLE PORTD.0
GOTO MAIN
ENDIF

ENDIF

'CHECK IF OVERRUN HAS OCCURRED:

IF OERR=1 THEN
Serout2 test,BAUD,["OERR",10,13] 'FOR DEBUGGING SHOW ERROR
CREN=0 'STOP CONTINUOUS RECEIVE
CREN=1 'RESTART CONTINUOS RECIEVE & CLEAR THE FLAG

BYTECOUNTER=0 'RESET COUNTER
GOTO GETDATA
ENDIF

ENDIF

RESUME

ENABLE
'===============================================


MAIN:

ON INTERRUPT GOTO GETDATA

if counter= 5000 THEN 'SEND PELCO VALUE EVERY FEW LOOPS

serout2 test,BAUD,["BUFFER=",HEX BUFFER.0,HEX BUFFER.1,10,13]
'(JUST CHECK 1ST 2 VALUES)

toggle portd.1 'LED TO INDICATE TO ME THAT THE LOOP IS LOOPING

counter=0
else
counter=counter+1
endif

goto main

end

[crhomberg]

I modified my code and am getting the 8 bytes but seem to keep running into buffer overflows. Can you see an error in my interrupt routine?

'************************************************* ***************
@ device hs_OSC, wdt_on, pwrt_on, protect_off
define osc 20
Include "modedefs.bas"
trisc.6=0
TRISC.7=1
TRISA.0=0


RCSTA = %10010000 ' ENABLE USART AND SET TO CONTINUOUS RECEIVE
SPBRG = 64 'SET TO 4800bps
INTCON = %11000000 'ENABLE GLOBAL & PERIFERAL INTERRUPTS
RCIF VAR PIR1.5 'FLAG IS THE INTERRUPT WHEN A BYTE IS IN THE USART BUFFER
RCIE VAR PIE1.5
OERR VAR RCSTA.1
CREN VAR RCSTA.4
test var porta.0
BAUD CON 16390


BUFFER VAR BYTE[10] 'BUFFER FROM USART TO COLLECT THE 8 BYTES
BYTECOUNTER VAR BYTE 'USED TO COUNTER BYTES INTO THE BUFFER
BFULL VAR BIT 'FLAGS THAT THE BUFFER HAS ALL 8 BYTES
VALUE VAR BYTE 'A TEMP SINGLE BYTE RECEIVED FROM THE USART
COUNTER VAR WORD 'USED FOR LOOP IN MAIN PROGRAM


BUFFER = 0
BYTECOUNTER = 0
BFULL = 0
VALUE = 0
RCIE=1 'ENABLE USART RECEIVE INTERRUPT FLAG

ON INTERRUPT GOTO GETDATA

GOTO MAIN:


disable
'====================INTERRUPT ROUTINE ==============================

GETDATA:


IF RCIF=1 THEN

VALUE=RCREG
IF VALUE = $A0 THEN 'CHECK TO SEE IF THE BYTE IS THE START BYTE
BYTECOUNTER=0
ENDIF

RCIF=0

IF BYTECOUNTER < 8 THEN
BUFFER[BYTECOUNTER] = VALUE
BYTECOUNTER=BYTECOUNTER+1
ENDIF

'CHECK IF OVERRUN HAS OCCURRED:

IF OERR=1 THEN
Serout2 test,BAUD,["OERR",10,13] 'TO SHOW OVERFLOW
PAUSE 1000
CREN=0 'STOP CONTINUOUS RECEIVE
CREN=1 'RESTART CONTINUOS RECIEVE & CLEAR THE OVERRUN FLAG
BYTECOUNTER=0 'RESET COUNTER AS PART OF PACKET HAS BEEN LOST SO START AGAIN
BUFFER=0
GOTO GETDATA
ENDIF

IF BYTECOUNTER=7 AND BUFFER[0]=$A0 AND BUFFER[6]=$AF THEN

GOTO MAIN
ELSE
GOTO GETDATA
ENDIF
ENDIF





RESUME

ENABLE
'================================================= ====================================

MAIN:

'ON INTERRUPT GOTO GETDATA

if counter= 1000 THEN 'SEND PELCO VALUE EVERY FEW LOOPS
serout2 test,BAUD,["BUFFER=",HEX BUFFER[0],",",HEX BUFFER[1],",",HEX BUFFER[2],",",HEX BUFFER[3],",",HEX BUFFER[4],",",HEX BUFFER[5],",",HEX BUFFER[6],",",HEX BUFFER[7],10,13] 'JUST CHECK 1ST 2 VALUES
toggle portd.1 'LED TO INDICATE TO ME THAT THE LOOP IS LOOPING
counter=0
else
counter=counter+1
endif

goto main

end

'================================================= ====================================