How to read the SD Card ID number?

Question

How can I programatically read the SD Card's CID register, which contains a Serial Number and other information? Can I do it through Android Java, or Native code?

Thanks in advance, Eric

Answer 1

Even though the relatively ancient Palm OS and Windows Mobile OS devices are able to read the SD card ID, AFAIK Android devices aren't capable of doing that yet. This is particularly troubling given the problems with the Settings.Secure.ANDROID_ID discussed here.

Answer 2

The only code I've found thus far to provide the id is C++ or C# http://jo0ls-dotnet-stuff.blogspot.com/2008/12/read-secure-digital-sd-card-serial.html
http://jo0ls-dotnet-stuff.blogspot.com/2008/12/read-cid-and-csd-c-implementation.html
If you are a C++ developer you may be able to take this and make it work on Android.

Answer 3

There is no Android API that can do this that I am aware of and for a general solution that is needed. To provide some background the SD card is connected to a hw-controller that is specific to the device platform. It is possible to read out the cid value from the linux /sys file system if you know your platform. The following snippet works on my droid (TI omap based platform) but not on Qualcomm MSM based platforms.

try {
        BufferedReader input = new BufferedReader(new FileReader("/sys/devices/platform/mmci-omap-hs.0/mmc_host/mmc0/mmc0:aaaa/cid"));
        String sd_cid = input.readLine();
        Log.i("CID_APP", sd_cid);
    } catch (Exception e) {
        Log.e("CID_APP","Can not read SD-card cid");
    }

On a another platform the sys file we are looking for is different. It may even differ between different cards on the same platform since I was not able to test that. On MSM based devices the path would be something like /sys/devices/platform/msm_sdcc.1/mmc_host/...

Since we have this hardware dependence on reading out the SD-card CID there would have to be an update to the Android API:s that provides general access. This API would then have to be implemented by each device manufacturer to map to the correct sd card controller driver.

Answer 4

As BMB wrote, you cannot know the real path of the SD card in the /sys filesystem. However, /sys implements aliases as well, and you may be able to retrieve the CID through /sys/block/mmcblk0/device/cid.

For example, on a Tattoo running 2.2, /sys/block/mmcblk0 is a soft link (established automatically by the system) to /sys/devices/platform/msm_sdcc.2/mmc_host/mmc1/mmc1:aaaa/block/mmcblk0.