Instant Interrupts Questions

[Darrel Taylor]

Hi JosueCas,

Thanks! Nice to know it's working!

I'm still trying to write up a good explanation of how it all works. That's why the thread is still closed. Hopefully I can answer most of the questions there.

But in your case, the RX interrupt works a little different. It's Flag bit gets reset by hardware whenever you read from the RCREG register, and can't be reset by software.

So inside a RX interrupt routine you MUST read from RCREG, or you'll end up in an Continuous Interrupt Loop.

Also, the HSER defines only work if you are using PBP's HSERIN/OUT, so the USART must be set up manually. OR, you can use this macro...

'--[ Initialize USART for specified baud rate at current OSC speed ]------------
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

Then to initialize the USART, just do this...

@ USART_Init  9600

With this macro you can also change the baud rate at any time. Unlike the Define's.
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[Josuetas]

You where right, tx a lot, the most important isue was with the configuration, i used a simple Hserout [0] at the begining and it all worked.

By the way!, i cant get the interruption system to work either in my 18f452 or in my 16f628, in 628 it says something like wsave5 being in the wrong bank, i am not at home right now. What must be done to work with different devices? I REALLY LIKE THIS STUFF!!!

Thanks AGAIN!

[Darrel Taylor]

My pleasure Josue,

The program currently only works with 14-bit cores, so for now, it won't work with 18-F's.

For the 628,
Although it has 4 banks, bank 3 doesn't have any General Purpose Registers in it. This causes one of the variable assignments to fail.
It does have access memory that's common to all banks at $70 which can be used instead.

Open the DT_INTS-14.bas file, and at the top you should see this section...

wsave       var byte    $20     SYSTEM      ' location for W if in bank0
'wsave       var byte    $70     SYSTEM     ' alternate save location for W 
                                            ' if using $70, comment out wsave1-3

' --- IF any of these three lines cause an error ?? ---------------------------- 
'       Comment them out to fix the problem ----
' -- It depends on which Chip you are using, as to which variables are needed --
wsave1      var byte    $A0     SYSTEM      ' location for W if in bank1
wsave2      var byte    $120    SYSTEM      ' location for W if in bank2
wsave3      var byte    $1A0    SYSTEM      ' location for W if in bank3
' ------------------------------------------------------------------------------

Comment out all the wsave? lines, and un-comment the 'wsave var byte $70

Then you should be good to go.
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[Josuetas]

Hi, i spent the last couple of days with a program that uses 6 interruptions, i am glad to say that everything works fine until now. I am using RX, TX, Timer0, Timer1, INT and portB interrupts. I REALLY DONT KNOW HOW I MADE IT BEFORE THIS STUFF!!.

I didn´t wanted to start a new post so i will use this conversation and all your knowledge and disposition with me to move on the questions.

1. How do you disable/reenable an interrupt? i mean in this system and to avoid using registers.
2. Is there any constrain about the handlers lenght? i am using a very large RX handler that seems to work by now, is it better to go to subroutines from the handler to come back later and make the codespace of the handler small?
3. Out of topic but really interesting to me, how can i work with an array? for example an 8 rows x 10 bytes array? is there any way in pbp (i have read the manual but there is nothing about it).
4. How can i avoid filling my memory program with LCDOUT sentences? they seem to be very consuming...
5. What is the difficulty about using this system in 18f452 like devices, i recall using interrupts in them and it was much more easier than in the 877.
6. To many questions? cause i got one more.. also offtopic
7. I am using a matrix keyboard with portbchange interruption, but i am losing time (missing the tmr1 int) while i wait for the user to release at the kb, any other great piece of code you have under your pillow to help me solve this?.


By the way i could solve the issue with the 628, you will have to make a MANUAL for this , maybe i can end up doing it for you

Thanks a loTTTT

[Darrel Taylor]

>> 1. How do you disable/reenable an interrupt? i mean in this system and to avoid using registers.

There are 2 macros, INT_ENABLE and INT_DISABLE.

@  INT_DISABLE  TX_INT   ; Disable USART Transmit interrupt
@  INT_ENABLE   TX_INT   ; Enable USART Transmit interrupt
@  INT_DISABLE  INT_INT  ; Disable external INT interrupt

>> 2. Is there any constrain about the handlers lenght?

The biggest thing to worry about is Time. &nbsp; If the interrupt handler takes a long time to do something, you run the risk of missing other interrupts. &nbsp; In general, the interrupt handler should be as short as possible, and it should NEVER contain pauses or routines that wait for something external to happen.

This forces you to think a little differently when writing interrupt driven programs. For instance, for USART RX, the interrupt handler should only be receiving the byte and placing it in a buffer. Don't try to HSERIN a whole string because it will take too long.

After placing the byte in a buffer, you would set a Flag to indicate that a byte is waiting, then somewhere in the main loop, the program should test that flag to see if it needs to do something with the data that has arrived.

As another example, say you measure a pulse width using Capture Mode. The interrupt handler will only grab the CCP1H:CCP1L value and save it to a variable, to be processed later in the main program. Attempting to Calculate the Actual Pulse width with complex formulas will take many hundreds, or even thousands of instruction cycles to complete, and any other interrupts that happen in the mean time will be lost.

>> 3. ...how can i work with an array? for example an 8 rows x 10 bytes array?

PBP doesn't have Multi-Dimensioned arrays, but it's easy enough to just make one big array and calculate the offset into it to accommodate the Rows.

array  VAR BYTE[80]
Row  VAR  BYTE  ' 0-7
COL  VAR  BYTE  ' 0-9
Temp VAR  BYTE

Row  = 4
Col  = 8
Array(Row*10+Col) = 69   ' Put 69 in Array(4, 8)
Temp = Array(Row*10+Col) ' Get value of Array(4, 8)

>> 4. How can i avoid filling my memory program with LCDOUT sentences?

http://www.picbasic.co.uk/forum/showthread.php?t=1999


>> 5. What is the difficulty about using this system in 18f452 like devices

The 18F interrupts can have either a High or Low priority. A high Priority interrupt can interrupt a Low priority interrupt that has already triggered. &nbsp; This presents some HUGE problems for the Instant Interrupt system, especially when using PBP Ints. The problems are not insurmountable, just HUGE.

>> 6. To many questions?

Yes.

>> 7. I am using a matrix keyboard with portbchange interruption, but i am losing time (missing the tmr1 int) while i wait for the user to release at the kb

Again, never wait for anything in an interrupt handler. With RBC_INT, you'll start with all PORTB 3:0 set to Output Low, so that when the user presses a button you will get an interrupt. At this point scan the keypad real quick to see which button was pressed. Then set the bottom 4 bits back to Low again. Now, Read PORTB one more time before exiting (very important) to end any mis-match condition.

When the user releases the key, you will get another interrupt. Do the same thing again. But this time you should scan that no keys are pressed. Keep track of the Presses and Releases in the routine. Of course de-bouncing becomes more difficult too.

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[Josuetas]

Ok, I will get my hands to work.
It seems like i will have to rewrite most of my code as i began to have problems just today before reading your post.
i will surely have all your answers in mind,

TX Again,


Yoshua

[jheissjr]

Even though the interrupts for 18F's are more complicated, do you plan on making the code work for them sometime in the future. I wish I was fortunate enough to know assembly as well as you do. I have been reading in the 18F datasheets and they say you can enable and disable the interrupt priority feature. Would disabling the priority make it more doable. Or if not, maybe something like setting all the interrupts to either high priority or to all low priority. Anything I can do to convince you to do take on the task for us