I am able to get unique 'Volume Serial Numbers' from the SD card when using the dir command in MS-DOS, though this number changes every. How To Read CID on SD card If you are looking to. Some also call this “reading the PSN off the SD card” or reading the product serial number off the SD card. Building on Dinesh's answer. Dinesh suggested looking in the directory /sys/class/mmc_host/mmc1/mmc1:*/ (where * is a number) for the file named cid, which gives us the contents of the card's CID register. ![]() This is does work in many cases, and is a very helpful start. But mmc1 is not always the removable SD card. Sometimes, e.g. On a Motorola Droid Pro with Android API level 10, mmc0 is the removable SD card, and mmc1 is something else. I'm guessing that mmc1, when present, points to internal storage of some sort (possibly a non-removable microSD card). On a cheap Android tablet we tested, mmc0 is the SD card and there is no mmc1. So you can't just assume that mmc1 is the SD card. A glimmer of hope: It seems (so far) that by looking at the type file in the same directory as the cid file (e.g. /sys/class/mmc_host/mmc1/mmc1:0007/type), we can determine which is which: a type value of SD indicates a removable SD card, while MMC is not. However, that's just from testing on a few Android devices. I can't find any specifications about the contents of the type file, so if somebody else knows of relevant documentation, please let me know. Of course, MMC and SD are just two different storage technology standards, and SD is backward-compatible with MMC. So it's not necessarily the case that type SD always corresponds to an external microSD card. It doesn't seem likely that MMC could indicate a microSD card at all (if the type field is populated accurately); but on the other hand, it's conceivable that a non-removable SD card could have type SD. For further research: Does this approach work when an microSD card is connected via a USB adapter? My one test on this, with a tablet, had the USB-connected microSD card show up as mmc1, with type SD. How To: Read CID on SD card May 24, 2012,,,, How To Read CID on SD card If you are looking to, or extract the CID off an SD card then you’ve find this article very helpful. Some also call this “reading the PSN off the SD card” or reading the product serial number off the SD card. Most phones and much of the software on phones will lock in to the CID number of a SD card. The CID number is a unique card identifier number that is unique to the card itself. The CID number is valuable because software developers and hardware developers can lock software to the unique number of the device thus eliminating the ability to pass along licensed software. Reading the CID number from an SD card is not an easy task. It requires specific access codes to the index table of the memory card, and unless you know how to use the SD chipset of your card reader, chances are you wont get the numberor least the correct and accurate number. What is the CID number of an SD card? The CID register is 16 bytes long and contains a unique card identification number. It is programmed during card manufacturing and cannot be changed by SD Card hosts. The CID number is a compilation of information about the card, such as manufacturer, date manufactured, checksum total, GB size and more. Below is a table outlining all the items which make up the SD CID number. So with all this said, how do you read the CID number from an SD card? As we’ve mentioned it isn’t easy and it’s [more or less] hardware based. If you do enough searching on the internet you’ll find some home-brew code to read the CID numbers, but that’s only if you have the SD card or microSD card connected via an IDE bus to your host computer. This isn’t easy for everyone. There is clear evidence that using a USB to SD card reader will not get you the information you require, or at least accurate and correct information.
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