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SD card extender
#1
I purchased a SD card extender for my system one so I wont have to bender over to get to it. It does not recognize it even after formatting.
Has any one used an extender with good results?

Thanks, Brad
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#2
(10-16-2014, 06:15 PM)car54 Wrote: I purchased a SD card extender for my system one so I wont have to bender over to get to it. It does not recognize it even after formatting.

I have never heard of an SD card extender, but I have used a micro-to-standard adapter and it didn't work worth a darn. The problem is that you double the number of places where the connection can go bad. And, in my estimation, the design of the SD card connectors and the jacks they mount in is crap.

I can't wait until I can get a device that the CPAP machine thinks is an SD card, but is really an SD card plus Bluetooth. Then once the card is solidly connected in the CPAP machine I can just leave it there and gather the data by radio.
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#3
(10-16-2014, 06:15 PM)car54 Wrote: I purchased a SD card extender for my system one so I wont have to bender over to get to it. It does not recognize it even after formatting.
Has any one used an extender with good results?

Thanks, Brad
You will find this unlikely to work due to signal attenuation, SD cards are not meant to be interfaced in this way.

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#4
(10-16-2014, 06:15 PM)car54 Wrote: I purchased a SD card extender for my system one so I wont have to bender over to get to it. It does not recognize it even after formatting.
Has any one used an extender with good results?

Thanks, Brad

car54.... now there's a great "handle." That TV show takes me back.
They do make extenders using a ribbon cable. I see no reason why one would not work with a speed category 2 card -- except perhaps build quality of the part. I take it your machine is on the floor?

[Image: 51R3NZWbCZL.jpg]
[Image: daD6uvCm.jpg]
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#5
I would expect it to work just fine so long as it isn't over 18" long. Try a replacement since you may have a defective unit.
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#6
The one I have is like the picture. I tried a few different cards and the system one did not recognize any of them. It wanted to format them but when I pressed yes for formatting, it did nothing. The extension cord is usable on my desktop computer.

What factor does 20 inches have to do with it( my is about 20) and what about the speed class of the card?

Yes, the unit is on the floor to reduce noise.

Car54, yes, I remember the series. I used to race cars and 54 was my #. One time I spun out and ended up in the brush where the corner workers could not see me. "Car54 where are you?"

Thanks for any future answers, Brad
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#7
The short answer as to cable length on a flat ribbon cable is the longer the cable is the more it is prone to crosstalk. Crosstalk occurs due to the mutual capacitance between the wires and varies as a function of the speed (frequency) of the data transmission. Some hardware systems are more tolerant of crosstalk than others. The more sophisticated (expensive) systems are often best at handling crosstalk and differentiating it from the useful data.

Crosstalk is the bane of data transmission via cables and can be minimized by various means, one of which is limiting cable length. Other methods can be twisting opposing data lines together to cancel out the resultant crosstalk product. Another method is to place a neutral or grounded conductor between data pairs to act somewhat as a shield to minimize crosstalk. In some cases the data transmission frequency may resonate with the line length and produce standing wave nodes that can be troublesome so special measures must be taken to avoid certain lengths of data cable.

You may need to contact PR for their guidance on what may work with their units.
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#8
(10-19-2014, 10:43 PM)surferdude2 Wrote: The short answer as to cable length on a flat ribbon cable is the longer the cable is the more it is prone to crosstalk.

There are a lot of problems that can happen if you use a long cable with something intended for short leads. Crosstalk is one. There is also increased inductance, capacitance, and resistance in the cabling. This can mess up the shape of the waveforms. If the impedances aren't carefully matched, you can get reflections and "ringing" of the signals. Some of the advanced high speed data techniques are even affected by the factor of how long it takes the signal to travel down the cable and return back to the source.

The circuitry in the card reader in the machine and in the SD card are designed to send data quickly through very short, controlled wires between the card and the chip it talks to. Adding a longer cable can break the process in several ways. Some of these problems can be fixed by the right cable in some cases, but some of them can't.

Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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#9
(10-20-2014, 07:27 AM)archangle Wrote: There is also increased inductance, capacitance, and resistance in the cabling. This can mess up the shape of the waveforms. If the impedances aren't carefully matched, you can get reflections and "ringing" of the signals. Some of the advanced high speed data techniques are even affected by the factor of how long it takes the signal to travel down the cable and return back to the source.

Those factors have the greatest effect on analog signals but much less on digital data.

Here's the drill on using an SD extension cable and it will help explain why it has little to offer in making access easier:

To use an SD extension cable successfully, you must first insert the SD card into the cable socket before plugging it in to the cpap slot. If you plug the cable in without the card inserted, the card will not be detected when it is inserted. In short that means you will not be allowed to "hot swap" the SD card but could hot swap the cable with the card inserted. As you can see, that means you have to bend over and perform the same act that you are trying to avoid. That's a "catch 22" at its finest.

Sometimes it seems like the simple things aren't as simple as we think.
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#10
(10-20-2014, 09:15 AM)surferdude2 Wrote: Those factors have the greatest effect on analog signals but much less on digital data.

That's not really that true with many modern, high speed data interfaces. The devices are designed to get the maximum data rate on the cabling involved. They often skirt close to the edge of what is possible. The right type and length of cable is more important than ever for some of the interfaces.

If the analog voltages and timings on the cable are distorted enough, the device on the other end won't "see" the correct digital signal. With SD cards, you're taking something intended to talk over an inch or so of wiring and putting a foot or so of cable. The circuitry may simply not be able to handle that much degradation of the signal.

Digital vs. analog does matter in that you get a 100% accurate signal until the signal quality gets bad enough that you start getting data errors. Many of the modern interfaces run at close to the maximum capability of the design and don't have a lot of room for error when you start changing the cabling.
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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