On 11/13/19 1:26 PM, Dietmar Schwertberger wrote:
On 13.11.2019 21:20, R.Wieser wrote:
300us is getting on towards realtime.
Not really. Translated to a frequency (toggeling the pin) it would be just
1.6 KHz. Thats rather slow for an ARM machine running on 1.4 Ghz (about a
million times as fast).
It *is* real-time...
Real-time is not about speed, but about guaranteed timing.
Yeah, that's always the conversation, but at the end of the day "realtime" is
always a question of "by how much". Do you really need to be hard periodic with
0 ns slop in either direction? Can you afford to come in early but not late?
By 10%? By 1%? By .01%?
If you can afford 1% and you need a 1 second interval, you're only asking for 10
ms and in practice even a giant preemptive non-RT OS like Linux can do it for
you. If you can only afford 1% on a 300 us interval then your lack of rigid
control over what happens on your processor is a real problem and you're better
off bare metal on a dedicated $2 Cortex-M than with random timeslices of the
1.4GHz beast on the rPi.
Is what I was shorthanding with "realtime".
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Rob Gaddi, Highland Technology -- www.highlandtechnology.com
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