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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: high frequency time stamping (Was: Simple Components 4.12 with
 MQTT implementation released)
Date: Tue, 19 Apr 2016 15:35:19 +0200
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Date: 2016-04-19T15:35:19+02:00
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On 19/04/2016 14:59, G.B. wrote:
> On 19.04.16 14:43, Dmitry A. Kazakov wrote:
>> It is a value and a time stamp, because data are oversampled. There is
>> no way a conventional OS could respond to each change at this rate.
>
> Is it possible to have a volatile variable T representing
> some point in time and a CAS discipline so that
>
> 1. there is one task that updates T at regular intervals and
>
> 2. another task that reads T for stamping items more frequently
>     than the first would write updates?

It is an interesting question. Do you mean CAS = content-addressable 
storage? I don't think it were possible to do.

We use a blackboard storage with a notification event signaling that the 
local consumer tasks may inspect the latest contents without blocking 
the producers.

The oversampling hardware deploys a buffer that can be read out. It 
basically is a soft of blackboard too. Clearly ADCs run asynchronously 
most of the time and there is no way you would wait for an ADC, it would 
take to much time. So pull methods do not work in most cases.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de