Emmc Cid Decoder 🆓

Most Linux systems expose the CID via sysfs. Run:

cat /sys/block/mmcblk0/device/cid

That outputs a 32-character hex string (128 bits). Example:

150100303136473332e03f5d9600b46d

Now, let’s decode it using a simple Python snippet or an online tool.

Quick manual decode (offsets, 0-indexed): emmc cid decoder

cid = "150100303136473332e03f5d9600b46d"
mid = cid[0:2]          # 0x15 (Kingston)
oem = cid[2:6]          # 0x0100
pnm = bytes.fromhex(cid[6:18]).decode()  # "016G32"
prv = cid[18:20]        # 0xe0 → revision 1.0?
psn = cid[20:28]        # 0x3f5d9600
mdt = cid[28:32]        # 0xb46d → year/mon decode

Or use mmc-utils:

sudo mmc extcsd read /dev/mmcblk0 | grep -i cid

For offline or batch decoding, Python scripts are ideal. Below is a simple yet complete eMMC CID decoder.

#!/usr/bin/env python3
# eMMC CID Decoder
import sys
def decode_emmc_cid(cid_hex):
cid_bytes = bytes.fromhex(cid_hex)
if len(cid_bytes) != 16:
raise ValueError("CID must be 32 hex chars (16 bytes)")
# MID
mid = cid_bytes[0]
manufacturers = 0x15: "Samsung", 0x11: "Toshiba", 0xFE: "SanDisk", 0x45: "Sandisk", 0x03: "Hynix", 0x01: "Samsung", 0x00: "No manufacturer"
print(f"Manufacturer ID (MID): 0xmid:02X (manufacturers.get(mid, 'Unknown'))")
# OID
oid = cid_bytes[2]
print(f"OEM ID (OID): 0xoid:02X")
# Product Name (PNM) - bytes 3 to 8 (6 chars)
pnm = cid_bytes[3:9].decode('ascii', errors='ignore').strip('\x00')
print(f"Product Name (PNM): pnm")
# Product Revision (PRV)
prv = cid_bytes[9]
rev_major = (prv >> 4) & 0x0F
rev_minor = prv & 0x0F
print(f"Product Revision (PRV): rev_major.rev_minor (BCD)")
# Serial Number (PSN) - bytes 10,11,12,13
psn = int.from_bytes(cid_bytes[10:14], byteorder='big')
print(f"Serial Number (PSN): psn (0xpsn:08X)")
# Manufacturing Date (MDT) - bits from byte 14 (nibbles)
mdt_byte = cid_bytes[14]
year_nibble = (mdt_byte >> 4) & 0x0F
month_nibble = mdt_byte & 0x0F
# Year offset from 1997 (JEDEC standard)
year = 1997 + year_nibble
print(f"Manufacturing Date: year:04d-month_nibble:02d (nibble year offset)")
# CRC7
crc_byte = cid_bytes[15] >> 1
print(f"CRC7: 0xcrc_byte:02X")

if name == "main":
if len(sys.argv) != 2:
print("Usage: python emmc_cid_decoder.py <32-char-hex-cid>")
sys.exit(1)
decode_emmc_cid(sys.argv[1])
 Most Linux systems expose the CID via sysfs

Save as cid_decoder.py and run:

python cid_decoder.py 1501004242473541021A79C0D5012B

The last 7 bits of the CID (bits 7:1) contain a checksum. Advanced decoders verify this CRC. If the CRC is invalid, the CID may have been corrupted due to a bad read or failing chip. That outputs a 32-character hex string (128 bits)