OTP Usage Tutorial#

What is OTP?#

OTP (One-Time Programmable) is a non-volatile area inside the chip used to store security configuration, key indices, calibration data, or device identity information. CanMV K230 currently provides OTP data read and read/write lock status query interfaces in machine.OTP.

OTP content is usually related to device security status, and read results may contain device-related information. The example only demonstrates reading and querying lock status. Please avoid exposing complete OTP output in actual use.

K230 OTP Features#

Feature	Description
Instance model	`OTP()` returns a singleton object, multiple calls return the same instance
Address range	`0x000` to `0xFFF`
Address alignment	Address must be 4-byte aligned
Single read length	1 to 1024 bytes
Boundary limit	A single read cannot cross the `0x400` boundary
Lock status	Supports querying `OTP.NA`, `OTP.RO`, `OTP.RW`

Application Example: Reading OTP and Querying Lock Status#

This example demonstrates how to create an OTP object, read data from a specified address, and query the lock status of several 4-byte aligned addresses.

Example Code#

from machine import OTP
import binascii


def lock_name(lock):
    if lock == OTP.NA:
        return "NA"
    if lock == OTP.RO:
        return "RO"
    if lock == OTP.RW:
        return "RW"
    return "UNKNOWN"


otp = OTP()

# OTP is a singleton object, calling OTP() again returns the same object.
print("same OTP object:", otp is OTP())

# Read data from a 4-byte aligned OTP address.
# Up to 1024 bytes can be read at a time, and cannot cross the 0x400 boundary.
data = otp.read(0x000, 32)
print("OTP[0x000:0x020]:", binascii.hexlify(data))

# Query the lock status of 4-byte aligned addresses.
for addr in (0x000, 0x004, 0x400, 0xC00):
    lock = otp.get_lock(addr)
    print("OTP[0x%03x] lock: %s (%d)" % (addr, lock_name(lock), lock))

Interface Description#

Method Name	Description
`OTP()`	Get the OTP singleton object
`read(addr, length)`	Read byte data from the specified OTP address
`get_lock(addr)`	Query the OTP lock status of the specified address

Example Analysis#

Get the OTP object otp = OTP() returns the OTP singleton object. When OTP() is called multiple times in a program, the same object is obtained.
Read OTP data otp.read(0x000, 32) reads 32 bytes of data starting from address 0x000, and the return value type is bytes.
Query lock status otp.get_lock(addr) returns the lock status of the specified address, which can be compared with the constants OTP.NA, OTP.RO, OTP.RW.

Lock Status Description#

Constant	Value	Meaning
`OTP.NA`	0	No Access, not accessible
`OTP.RO`	1	Read Only
`OTP.RW`	2	Read Write

Notes#

addr must be within the range 0x000 to 0xFFF, and must be 4-byte aligned.
length must be within the range of 1 to 1024 bytes.
A single read cannot cross the 0x400 boundary, for example, reading 32 bytes from 0x3F0 will fail.
The current machine.OTP only provides read and lock status query interfaces, and does not provide write or lock interfaces.
OTP data may contain device security-related information. Please confirm the usage scenario before printing or saving.

OTP Usage Tutorial

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