y). Then I thought a proper function
would be better but got stuck in that expression "sleep resolution"
For that scale (10 SYSCLK cycles), a loop is probably OK but I wanted to
make sure there's not a more appropriate system tool
El mié, 24 mar 2021 a las 10:46, Sara d
On Thu, Mar 25, 2021 at 2:22 PM Grr wrote:
> > 1nsec means 1GHz, it is very hard to achieve the required accuracy even
> > with the high end CPU. But since the standard defines nano_sleep,
> up_ndelay
> > looks not so unreasonable.
> >
>
> I don't mean 1 ns
>
> I mean delays in the order of _doze
> 1nsec means 1GHz, it is very hard to achieve the required accuracy even
> with the high end CPU. But since the standard defines nano_sleep, up_ndelay
> looks not so unreasonable.
>
I don't mean 1 ns
I mean delays in the order of _dozens_ of ns
100 MHz (a very reasonable frequency nowadays) mea
On Thu, Mar 25, 2021 at 5:25 AM Grr wrote:
> Why not use msec & usec delays?
>
> Because the need is nsec delays
>
>
Ok, I understand.
> My question is:
>
> Why not add a portable, general purpose nsec delay function to Nuttx?
>
>
1nsec means 1GHz, it is very hard to achieve the required accura
Why not use msec & usec delays?
Because the need is nsec delays
My question is:
Why not add a portable, general purpose nsec delay function to Nuttx?
El mié, 24 mar 2021 a las 22:34, Xiang Xiao ()
escribió:
> Another way to avoid the calibration is to reuse the hardware timer in the
> busy loo
Another way to avoid the calibration is to reuse the hardware timer in the
busy loop:
https://github.com/apache/incubator-nuttx/blob/master/drivers/timers/arch_alarm.c#L60-L74
https://github.com/apache/incubator-nuttx/blob/master/drivers/timers/arch_timer.c#L122-L144
On Thu, Mar 25, 2021 at 11:42
Why not call up_udelay or up_mdelay? The arch/soc should provide a best
implementation for you.
I was wondering that too.
Also, as a side note, it is very important to calibrate the delay loop
using in those functions. If the delay loop is properly calibrated,
these can be very accurate (
general solution for this problem to
> the
> > Nuttx toolbox
> >
> > El mié, 24 mar 2021 a las 11:24, David Sidrane ( >)
> > escribió:
> >
> > > What HW is this on?
> > >
> > > -Original Message-
> > > From: Grr [mail
On Wed, Mar 24, 2021 at 4:49 PM Grr wrote:
>
> Since afterstart = 0, there should be no loop to optimize out except ONE
> value test
>
> One hundred cycles for that would seem excessive for me
>
> TWENTY THOUSAND CYCLES for a _zero_ loop?!?
>
> Maybe in Java
We didn't see the value of transfer->d
for(delay = 0; delay < transfer->dev->afterstart; delay++);
afterstart is loop's limit, which determines the desired delay length,
known by definition
El mié, 24 mar 2021 a las 14:57, Johnny Billquist ()
escribió:
> Well. There was nothing in there that showed me that afterstart == 0. Is
> this
Well. There was nothing in there that showed me that afterstart == 0. Is
this a known fact, or an assumption?
Johnny
On 2021-03-24 21:47, Grr wrote:
Since afterstart = 0, there should be no loop to optimize out except ONE
value test
One hundred cycles for that would seem excessive for me
T
Since afterstart = 0, there should be no loop to optimize out except ONE
value test
One hundred cycles for that would seem excessive for me
TWENTY THOUSAND CYCLES for a _zero_ loop?!?
Maybe in Java
El mié, 24 mar 2021 a las 14:30, Gregory Nutt ()
escribió:
>
> > Weird behavior:
> >
> > Simpl
Weird behavior:
Simply changing loop counter variable from uint16_t to volatile uint16_t
causes initial delay (with variable delay = 0) going from ~500 ns to ~120 us
The code is
uint16_t delay;
select_function();
for(delay = 0; delay < transfer->dev->afterstart; delay++);
Any ideas?
I ima
On Wed, Mar 24, 2021 at 3:53 PM Johnny Billquist wrote:
>
> Perfectly expected.
> With volatile, the compiler are not allowed to optimize away the memory
> accesses for updating the loop variable. So you are suddenly getting a
> lot of memory read/write cycles that probably didn't happen before.
>
r.
I started by an empty for loop but it seems optimization gets rid of it
(I
haven't researched the issue properly). Then I thought a proper function
would be better but got stuck in that expression "sleep resolution"
Add volatile to the loop counter variable an
seems optimization gets rid of it
> (I
> > haven't researched the issue properly). Then I thought a proper function
> > would be better but got stuck in that expression "sleep resolution"
>
> Add volatile to the loop counter variable and the optimizer will not
> remove it.
>
>
>
Is the Tickless mode considered stable enough for production use now?
IIRC it had some caveats when I last looked into it and I haven't had
a chance to study it again.
I believe so. I am not aware of any issues. It has been around for
several years and has been used by a lot of NuttX users.
On Wed, Mar 24, 2021 at 2:53 PM Gregory Nutt wrote:
>
>
> > The way the logic in clock_nanosleep() is written, the minimum delay
> > ends up being 2 such ticks. I don't remember why and I can't seem to
> > find it in the code right now, but I know this because I checked into
> > it recently and fo
The way the logic in clock_nanosleep() is written, the minimum delay
ends up being 2 such ticks. I don't remember why and I can't seem to
find it in the code right now, but I know this because I checked into
it recently and found out that that's how it works.
See https://cwiki.apache.org/conf
is rounded up to an integer multiple of the
> sleep resolution"
>
> What is the sleep resolution and where/how is defined?
I'm a little late to the party, but...
The resolution would likely be 20 milliseconds, which is far more than you want.
Here's how I get that 20
t a proper function
would be better but got stuck in that expression "sleep resolution"
Add volatile to the loop counter variable and the optimizer will not
remove it.
.
David
-Original Message-
From: Grr [mailto:gebbe...@gmail.com]
Sent: Wednesday, March 24, 2021 10:52 AM
To: dev@nuttx.apache.org
Subject: Re: Sleep Resolution
This is a SocketCAN driver for MCP2515 with a new SPI system that
streamlines the select->write->read->deselect proce
1 a las 11:24, David Sidrane ()
> escribió:
>
> > What HW is this on?
> >
> > -Original Message-
> > From: Grr [mailto:gebbe...@gmail.com]
> > Sent: Wednesday, March 24, 2021 10:09 AM
> > To: dev@nuttx.apache.org
> > Subject: Re: Sleep Resolution
> &g
uttx toolbox
El mié, 24 mar 2021 a las 11:24, David Sidrane ()
escribió:
> What HW is this on?
>
> -Original Message-
> From: Grr [mailto:gebbe...@gmail.com]
> Sent: Wednesday, March 24, 2021 10:09 AM
> To: dev@nuttx.apache.org
> Subject: Re: Sleep Resolution
>
>
, 2021 10:09 AM
> To: dev@nuttx.apache.org
> Subject: Re: Sleep Resolution
>
> Thank you very much for your response
>
> What I'm trying to do is to generate hold and disable times for SPI CS,
> which should be about 50 ns
>
> I started by an empty for loop but it
What HW is this on?
-Original Message-
From: Grr [mailto:gebbe...@gmail.com]
Sent: Wednesday, March 24, 2021 10:09 AM
To: dev@nuttx.apache.org
Subject: Re: Sleep Resolution
Thank you very much for your response
What I'm trying to do is to generate hold and disable times for S
Subject: Sleep Resolution
Hello to all.
Looking for the right way to create a _very_ short delay (10-100 ns), I
found clock_nanosleep, whose description says:
"The suspension time caused by this function may be longer than requested
because the argument value is rounded up to an integer multiple o
I
> found clock_nanosleep, whose description says:
>
> "The suspension time caused by this function may be longer than requested
> because the argument value is rounded up to an integer multiple of the
> sleep resolution"
>
> What is the sleep resolution and where/how is defined?
>
> TIA
> Grr
>
n
would be better but got stuck in that expression "sleep resolution"
For that scale (10 SYSCLK cycles), a loop is probably OK but I wanted to
make sure there's not a more appropriate system tool
El mié, 24 mar 2021 a las 10:46, Sara da Cunha Monteiro de Souza (<
saramonteiro
ion time caused by this function may be longer than requested
> because the argument value is rounded up to an integer multiple of the
> sleep resolution"
>
> What is the sleep resolution and where/how is defined?
>
> TIA
> Grr
>
Hello to all.
Looking for the right way to create a _very_ short delay (10-100 ns), I
found clock_nanosleep, whose description says:
"The suspension time caused by this function may be longer than requested
because the argument value is rounded up to an integer multiple of the
sleep resol
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