S9 - Still Checking SKEW ???

Nord wrote:

DreamDiver wrote: Meanwhile, if there is anyone out there who can explain the 250ms housekeeping window, I'd be grateful.

Hi DD

The "housekeeping issue" is basically a time out the media uses to check the read/ write details and make sure the the "checksum" is correct for the details that it wants to write.
That check or house keeping is done at 100ms or 250ms.
If the check is done and is correct... it will write the data.
If the check says incorrect... it will report that and not write the data.
In other words... there will be a small amount of data missing and causing a skew...

Nord

So it attempts to read the SD card every 100 or 250ms. Both or which?
Because it can't read and write at the same time, and because some cards have drastically higher CRC???, that means the card can't always be accessed to read, let alone write, which is four times slower on average. Am I understanding this?

DreamDiver wrote: The data is written to the sd card under three separate circumstances:
once a minute, perhaps to add detailed data and to update compliance data,
once every two minutes, perhaps to add hi-res data,
once immediately for each apnea or hypopnea.

Exactly which data is written at what period is not as important as just knowing that the data is written in such a manner.
In the example below, if you turn off the machine at the designated time and then remove the card before the last two minute session one minute session have finished writing, you'll see the example apnea show up in a place where there is perhaps pressure data but no flow data. It's as if it's hanging out there without out supporting flow data as proof because we didn't wait long enough for the last bit of data to write to the card.

I was writing, the same time you were illustrating it. I like your illustrations better...

Nord

DreamDiver wrote: So it attempts to read the SD card every 100 or 250ms. Both or which?
Because it can't read and write at the same time, and because some cards have drastically higher CRC???, that means the card can't always be accessed to read, let alone write, which is four times slower on average. Am I understanding this?

Not both... the faster cards do their house-keeping at 100ms... the slower at 250ms.
Not right... the card needs to read the data then write the same data to the card after that.
The checking is done by the card to make sure that it has the same data that it is going to write to the card.
This is what they call the timeout while it is doing a checksum.

It is a function of all media but is done at different speeds...
SD cards have a standard that they must be 100 or 250ms while doing this function.

Several members here have mentioned it before including Dave21, myself and I think, Kennethryan... but because we have pursued many "leads".
And really when alterego61 looked at the files, he didn't think that was the problem, so...

Nord

Tomorrow I'm going to post some info about the cards...
I'm going to sleep on it now.

Nord

Thanks for addressing my question, Nord. And thanks to you too, DreamDiver. Your awesome graphics were very helpful!

The skews we see in the ResScan graphs are caused by different timestamps in the header information of the detailed data files on the SD card.

The timestamps are written at the time the files are created, i.e. when the start/stop button is pressed to switch the blower on.

It is possible that corrupted data from the prior session could be causing this, if the card had been prematurely removed at the end of a previous session.

In my case though, I don't remember ever having removed the card less than 5 minutes after stopping the blower.

Now that I have re-initialized my card by formatting it, I will pay attention to waiting at least 5 minutes before removing it each morning so as to test this theory. At one mask event per day it took me just less than 2 weeks to get a skew started on my last card, so the test may take some time...

alterego61 wrote:The skews we see in the ResScan graphs are caused by different timestamps in the header information of the detailed data files on the SD card.

The timestamps are written at the time the files are created, i.e. when the start/stop button is pressed to switch the blower on.

It is possible that corrupted data from the prior session could be causing this, if the card had been prematurely removed at the end of a previous session.

In my case though, I don't remember ever having removed the card less than 5 minutes after stopping the blower.

Now that I have re-initialized my card by formatting it, I will pay attention to waiting at least 5 minutes before removing it each morning so as to test this theory. At one mask event per day it took me just less than 2 weeks to get a skew started on my last card, so the test may take some time...

Hi alterego...

Good to have you back again...
Will you be using the same card.
I also started this process of leaving the card for at least 5 minutes after shutting down.
I am not unplugging the S9 but I am power saving after the 5 minute period.
I also power up about 5 - 10 minutes before having a mask session.
I am also having 1 - 3 mask sessions per 24 hour period.
Started to day with formatting following SDA Panasonic format software on ResMed 1 Gig card.

I should end up with skewing sooner based on mask sessions...

Nord

All S9 user's...

There is a small pattern of machines that have/ don't have skew issues that I am seeing.

I am really looking for machines that have been in use for at least several weeks... 20 mask sessions ??
That have looked for Skew Issues and found NONE, SOME or MANY...

I'm looking to wrap this up in a week's time. PM me when you get a chance.

Nord

Nord, I sent you my machine's details by PM

Another bump for Serials... ???

Nord