原创 当SD卡无法识别时

    在TI的AM335X上跑linux3.2内核时出现下面的错误：

[root@EmbedSky /]# fdisk -l
end_request: I/O error, dev mtdblock0, sector 0
Buffer I/O error on device mtdblock0, logical block 0
end_request: I/O error, dev mtdblock0, sector 8
Buffer I/O error on device mtdblock0, logical block 1
end_request: I/O error, dev mtdblock0, sector 16
Buffer I/O error on device mtdblock0, logical block 2
end_request: I/O error, dev mtdblock0, sector 24
Buffer I/O error on device mtdblock0, logical block 3
end_request: I/O error, dev mtdblock0, sector 0
Buffer I/O error on device mtdblock0, logical block 0

Disk /dev/mtdblock1: 0 MB, 131072 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 byend_request: I/O error, dev mtdblock4, sector 0
Buffer I/O error on device mtdblock4, logical block 0
tes

Disk /devend_request: I/O error, dev mtdblock4, sector 8
Buffer I/O error on device mtdblock4, logical block 1
/mtdblock1 doesnend_request: I/O error, dev mtdblock4, sector 16
Buffer I/O error on device mtdblock4, logical block 2
't contain a valend_request: I/O error, dev mtdblock4, sector 24
Buffer I/O error on device mtdblock4, logical block 3
id partition table

Disk /dev/end_request: I/O error, dev mtdblock4, sector 0
Buffer I/O error on device mtdblock4, logical block 0
mtdblock2: 0 MB, 131072 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock2 doesn't contain a valid partition table

Disk /dev/mtdblock3: 0 MB, 131072 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock3 doesn't contain a valid partition table

Disk /dev/mtdblock5: 0 MB, 131072 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock5 doesn't contain a valid partition table

Disk /dev/mtdblock6: 3 MB, 3145728 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock6 doesn't contain a valid partition table

Disk /dev/mtdblock7: 5 MB, 5242880 bytes
255 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock7 doesn't contain a valid partition table

Disk /dev/mtdblock8: 257 MB, 257425408 bytes
255 heads, 63 sectors/track, 31 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

一开始以为是软件错误，但是同样的软件并没有在开发板上出错，而且end_request: I/O error, dev mtdblock0, sector 0似乎是引脚出错，仔细查了查原理图，发现SD卡的3与6管脚通过一个22pf的电容接地，导致这两个管脚有1V多的电压。将电容拆去短路，SD卡果然可以识别了。