Wes Zanardelli wrote:
>Frederic,
> I am just curious why you aren't using Pin 10 of the LPT port. If you
> use
>Pin 10, it is tied directly to IRQ 7. You can then have an interrupt servi
>ce
>routine that toggles pin 3 of your parallel port. It might be a good
>experiment to see if this improves your response time (I think it will
>especially if you are using a fast machine).
Well, it shouldn't make any difference: basically what I'm trying to measure
is NOT the interrupt latency, but the amount of time between the moment
the Interrupt Handler has been triggered and the moment the Real Time Task
has ben woken up.
I may need several real-time tasks running and need to know how long it will
take before a task gets woken up.
On the example I've been explaining in my original mail:
________ ________ ________
Interrupt ______| |______| |______| |____
.
. ________ ________ ________
Pin 2 ______.__| |______| |______| |____
. . .
. . _____.__ ________ ________
Pin 3 ______.__.__| . |______| |______| |____
. . . .
. . . .
t0 t1
`t0' will be the interrupt latency. this topic has already been discussed
quite a bit on this list
`t1' would be the `schedulaer latency' [a better name someone ?] which I'd
like to caracterize.
The values I got so far for `t1' are in the range: 19.6-25 usecs.
>> Hi folks,
>>
>> We are currently doing some experiment with RTL.
>>
>> Basically what we have been trying to measure so far is the task
>> scheduler latency:
>>
>> Real Time Clock ---> IT wake_up ---> RT Task
>> | |
>> V V
>> Toggle Pin2 Toggle Pin3
>> parallel port parallel port
>>
>> Using a scope we measure an average 22 micro-seconds between IT and Task.
>> [ best case 19.6 usecs, worst case 25 usecs ]
>>
>> Did you guys ever been able to get faster response time ?
>>
>> Thanks in advance for any advice!
--
Frederic.R.R.Roussel
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