From: "Øyvind Harboe" <oyvind.harboe@zylin.com>
To: Bart Veer <bartv@ecoscentric.com>
Cc: ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] HAL_DELAY_US() default implementation
Date: Sun, 26 Jun 2005 17:11:00 -0000 [thread overview]
Message-ID: <1119805895.10732.13.camel@localhost.localdomain> (raw)
In-Reply-To: <20050626142647.175E565C0A4@smtp.ecoscentric.com>
Getting rid of calibration is not easy.
Take the AT91 HAL variants specifically. There are 5'ish different
sub-hals * 3 types of memory(flash + internal/external RAM). Thats
15'ish combinations.
How about this approach?
- No automatic calibration
- Add a machine code busy loop/CPU type. Machine code is
used to make the busy loop independent of compiler optimisations
- Some(many?) HAL's have a HAL_DELAY_US() that works out
of the box according to the newest HAL_DELAY_US() specification and
hence won't need any calibration.
- If the user provides a CDL parameter which calibrates the busy loop
he gets HAL_DELAY_US(), otherwise he doesn't. It is better with a
compile time error than a broken HAL_DELAY_US().
- If a HAL knows that it can accuratly estimate this parameter in all
cases, it can provide a default value and HAL_DELAY_US() works out of
the box.
--
Øyvind Harboe
http://www.zylin.com
--
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prev parent reply other threads:[~2005-06-26 17:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-22 7:26 Øyvind Harboe
2005-06-26 14:26 ` Bart Veer
2005-06-26 17:11 ` Øyvind Harboe [this message]
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