SD card with extension cable

[engr_joni_ee]

Hi,
I am working with a new development board. I am wondering if it is possible to have SD card connector mounted on another adapter card that can be connected to the main development board with an extension cable. I guess there are four data lines, clock and cmd, in addition to power and common ground that should be in the extension cable. Is it possible to have 1.5 meter long extension cable between the SD card adapter card and the main development board ? What kind of cable is suitable for class 10 SD card ?

 

[dpaul]

I am wondering if it is possible to have SD card connector mounted on another adapter card that can be connected to the main development board with an extension cable.

Why is it important to have the connection via a 1.5m cable?

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[FvM]

SD card bus isn't designed for long cable connections. The physical bus specification allows a maximal signal line inductance of 16 nH, that's the equivalent of only a few cm transmission line.

 

[dick_freebird]

I'd suspect the higher speed SD cards would see
either an increased BER, or fall back to a lower
rate standard.

I'd hope that any extension cable has supplemental
decoupling at the far end.

 

[engr_joni_ee]

Any recommendation to find the SD card reader connectors with extension cable that can be attached to the main development board ?

 

[KlausST]

Hi,

A safe way could be to replace the single ended wires with a differential interface.
I'd use LVDs, but RS422 may work also. For sure one additionally needs to use suitable cables and termination...
In detail one needs to study datasheets.

Klaus

 

[FvM]

Hi,

A safe way could be to replace the single ended wires with a differential interface.
I'd use LVDs, but RS422 may work also. For sure one additionally needs to use suitable cables and termination...
In detail one needs to study datasheets.

Klaus

In the first place, you'll need level translators with cable drivers for the bidirectional SD data bus. Level translators are available to translate between 1.8V and 3.3V SD card bus, with automatic data direction switching but no cable driver feature.

There are also passive extender cables on the market with up to 50 cm length. They hardly comply with the SD card physical layer spec, but probably work by chance. As far as I'm aware of, there's usually no SD host speed fall-back based on signal quality, just an automatic speed switching according to the read card property register information.

 

[dick_freebird]

Is there a USB resource which could accept a USB
SD card R/W appliance?

Or, might you be better off just using a USB thumb
drive?