Sandisk extreme 32GB and 16GB dont initialize in XO-1.75

John Watlington wad at
Thu Oct 18 14:48:26 EDT 2012

Based on that error message, my guess is that those Sandisk cards are the
first to support +1.8V operation.   The kernel is detecting this, but getting
confused as it doesn't know how to turn on +1.8V power to the SD (it isn't
supported by that motherboard).

On XO-1.5, we supported operating SD cards at +1.8V, but since we never
encountered such a card the feature was dropped in XO-1.75/XO-4.   All cards
have to support operation at the +3.3V these systems provide.

The kernel should recognize this limitation, and not try to negotiate for
lower voltages.   This sounds like a bug in build 21, please file a ticket.


On Oct 7, 2012, at 7:33 AM, George Hunt wrote:

> Hi all,
> I've been working on a XO-1.75 as XS project. The smallest form factor XS would use an SD card for School Server storage. So I purchased fast, large SD cards from Amazon.  These cards work in my mac, and they initialize, and appear to work on the XO-1.5 running build 860.
> The XO-1.75 software is build 21 (12.1.0), firmware is Q4D17.
> The error message in the /var/log/messages is:
> Oct  7 11:18:44 schoolserver kernel: [157819.866661] sdhci: Switching to 1.8V signalling voltage failed, retrying with S18R set to 0
> Oct  7 11:18:44 schoolserver kernel: [157819.876896] mmc0: error -110 whilst initialising SD card
> In my reading about SD cards, I discover that some SD cards are not genuine. I have looked at /sys/... and the manufacturing number was "003" which is appropriate for sandisk.
> This error message is mentioned in 
> Ticket #11736
> I'd be happy to give more info, or do testing. 
> George
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