On 3/31/06, Lucian Copat <lucian.copat@audiotel.ro> wrote:
>
> I know that a message has at maximum 8 bytes in CAN, that's why I need
> to develop my own higher layer protocol to fragment the data. But when
> the interrupt is enabled, it doesn't activate if the buffer is empty,
> but when the buffer becomes empty (after having sent a CAN message).
>
> In this way, I can only avoid reentrance by writing the same code twice
> or by setting a flag in the interrupt.
>
> Lucian


I can't understand the problem here either if you use the method Gerhard
suggest.

1.) When you have data to send fill all free buffers. Enable interrupt.
2.) When you get a frame sent interrupt fill data again if any to all free
buffers.

No need to rewrite code use a function call to fill the buffers. It will
only be called by one process anyway and don't need to be reentrant.

/Ake



Gerhard Fiedler wrote:
>
> >Lucian Copat wrote:
> >
> >
> >
> >>My question regards the E-CAN module in PIC18F4680. I have a routine
> >>which loads a message (100 bytes max) into a temporary sending buffer.
> >>
> >>
> >
> >You know that a single CAN message can only have 8 bytes payload, right?
> >
> >
> >
> >>I would like that after loading this buffer, when I activate the TX
> >>interrupts, the ISR to be called if there are some free buffers. E-CAN
> >>module does generate an interrupt only when a buffer _becomes_ empty,
> >>which means I should load it first. If I load it first and also in ISR,
> >>I would have reentrant code. Is there any method to pass this problem ?
> >>
> >>
> >
> >You would typically disable the TX interrupt in the ISR when it sees that
> >there are no more bytes. Then, after initiating the next tx sequence, you
> >reenable it. This way, there's no problem with reentrance.
> >
> >Gerhard
> >
> >
> >
>
> --
> *Lucian Copat
> Software Team Leader
> Audiotel Comlabs
> E-mail: lucian.copat@audiotel.ro
> Mobile: (+4)0722.729.658
> Web: http://www.audiotel.ro*
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