Hi Rob,
it is possible to call a procedure from both the main program and from an
interrupt alternately, but I would try to avoid that, it's... I'd call it
dangerous.
As jal is not reentrant, you have to make absolutely sure, that no single part
of any procedure is running twice in any case. (The only exception I know of
are the multiplication/division functions which are safe to be called from an
interrupt while running in the main program, but those are not seen as
functions to the user anyway) That means, that if you use e.g. a print
procedure inside the interrupt, you also have to disable interrupts each time
you're using a similar print procedure in the main program. All decimal print
procedures use the same background code, so in this sense, they're "the same
procedure" and need to be surveyed not to run from both the main program and
the interrupt at the same time.
And, you should compile with --no-variable-reuse, as the compiler is probably
not aware of procedures being called from an interrupt.
Can be that you obeyed that rule by disabling interrupts when using I2C in the
main program. But then, there's hardware involved. You need to make sure that
the hardware is idle and in a reset, initialized state each time before
enabling interrupts. I'm not so familiar with the I2C peripheral to decide if
that's a problem. And, also all devices on the I2C bus need to be reset and
initialized each time the interrupt is enabled.
I do prefer handing over the alarm to the main program via volatile flag bit.
Greets,Kiste
Am Samstag, 19. Februar 2022, 09:58:53 MEZ hat rob...@hotmail.com
<rob...@hotmail.com> Folgendes geschrieben:
Hello all,
Some time ago I made a library for the clock IC DS3231. This library is part of
Jallib release 1.7.0.
This IC has an I2C interface and is capable of handling two alarms. When an
alarm is activated an interrupt is generated.
Reading the alarm flag from the IC also uses - of course- the I2C interface but
the I2C interface is also used by the main program.
I thought that if I would disable all interrupts when calling the I2C routines
from the main program and only enable it while not used by the main program
that I could call the same I2C routines from the interrupt routine and so be
able to read the alarm flag from the IC to see if alarm 1 or alarm 2 was
activated.
Unfortunately this did not work.
I thought that when an interrupt is called some info is saved and after the
interrupt restored but I also thought that I could then call any routine from
the interrupt as long that I am certain that no I2C transfer was active (which
should be since the interrupt is disabled when the main program is using the
I2C routines).
Any ideas why this does not work? Am I missing something?
What the current sample program does is just setting a global flag in the
interrupt routine and the main program polls this flag and then reads the alarm
flag of the IC via I2C but this undermines a bit the use of the interrupt.
Thanks.
Kind regards,
Rob
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