SDIO on external SD slot

[John Watlington]

On Mar 3, 2011, at 4:57 AM, Sridhar Dhanapalan wrote:

> Does the external SD slot on the XO-1.5 support SDIO?
> 
> I'm curious about the feasibility of developing a 3G modem that can
> fit into the slot. USB dongles can get broken or lost too easily.

Yes, the external slot does support SDIO (the only difference
from an electrical point of view is that the host interface needs
to allow the SD card to generate system interrupts by reusing
a data pin.)   It should be capable of maintaining power through a
suspend, just like the built-in WLAN.

I've been looking at 3G hardware, and you can now get a module
built which is the size of the WLAN card.  You still have to tackle:
- a miniPCIe is still bigger than an SD slot
- thermal issues
- power issues
- antennas, as the SD card is flush with the case
- SAR concerns

Have you considerd buying 3G Wifi access points instead ?
They will be cheaper than custom cards (unless you want > 50K),
are already available, and can be shared by multiple kids.
Plus, they come with their own battery !
Plus, they can be left in the book bag or on a shelf and arranged to
expose the child to less radiation.

Cheers,
wad

> Sridhar
> 
> 
> Sridhar Dhanapalan
> Technical Manager
> One Laptop per Child Australia
> M: +61 425 239 701
> E: sridhar at laptop.org.au
> A: G.P.O. Box 731
>      Sydney, NSW 2001
> W: www.laptop.org.au
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