SDIO on external SD slot

[Peter Robinson]

On Thu, Mar 3, 2011 at 3:10 PM, John Watlington <wad at laptop.org> wrote:
>
> 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.

Plus they can be used by multiple laptops.

Peter