In this guide, we will step-by-step guide you to use OPTTool (a software application) to burn OTP bits on SP7350 platforms.
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The status window of OTPTool indicates "CONNECT Success!" as shown above.
3 OTPTool Operations:
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The status window of OTPTool indicates "READ Start..…” and then “READ Success!" as shown above.
3.3 Write to OTP Bits
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After making all necessary modifications, click "Write" to write the changes to the OTP of the SP7350 platform. Refer to screenshot below, bit [543:512] is updated:
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4. Burning Secure-boot and Device Keys
The SP7350 supports secure-boot functionality. To activate secure-boot, it is necessary to build the code with security enabled and write secure keys into the OTP (One-Time Programmable) memory of the SP7350. There are two keys defined in the OTP - the secure-boot key for digital signatures and the device key for image decryption. Each key is 32 bytes long.
4.1 Burn Secure-boot Public Key (for digital signature) into OPT Bit 512 ~ 765
The secure-boot key is stored in the file build/tools/secure_hsm/secure/otp_Sb_keys/ed_pub_0.hex:
7BBBCF06A44BA7655540A7F8AD5176F4BCA83F00E63442A7BA0C4F5D8BBCF650
Convert the key to little-endian 4-byte words:
OTP[543:512] = 06CFBB7B
OTP[575:544] = 65A74BA4
OTP[607:576] = F8A74055
OTP[639:608] = F47651AD
OTP[671:640] = 003FA8BC
OTP[703:672] = A74234E6
OTP[735:704] = 5D4F0CBA
OTP[767:736] = 50F6BC8B
Input it to OTP words one by one. Afterward, check and then press "Write."
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The status window of the OTPTool indicates "WRITE Start..…” and then “WRITE Success!" as shown above.
Press 'Read' to read back content of OTP.
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The status window of the OTPTool indicates "READ Start..…” and then “READ Success!" as shown above.
4.2 Write Device Private Key (for decryption) into OTP Bit 768 ~ 1023
The device private key is stored in hex file build/tools/secure_hsm/secure/otp_Device_keys/x_priv_0.hex:
583D9479760D5229611A4601CB1EE80E2C0C7BE1E8F4C637A9EA72D5A5A3B25C
Convert the key to little-endian 4-byte word:
OTP[799:768] = 79943D58
OTP[831:800] = 29520D76
OTP[863:832] = 01461A61
OTP[895:864] = 0EE81ECB
OTP[927:896] = E17B0C2C
OTP[959:928] = 37C6F4E8
OTP[991:960] = D572EAA9
OTP[1023:992] = 5CB2A3A5
Input it to OTP words one by one. Afterward, check and press "Write."
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The status window of the OTPTool indicates "WRITE Start..…” and then “WRITE Success!" as shown above.
Press 'Read' to confirm the content of OTP.
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The status window of the OTPTool indicates "READ Start..…” and then “READ Success!" as shown above.
4.3 Enable Secure Mode of SP7350 (Write 1 into OTP bit 0)
Modify bit 0 to 1 and then press "Write."
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The status window of the OTPTool indicates "READ Start..…” and then “READ Success!" as shown above.
4.4 Enable MP Bit of SP7350 (Write 1 into OTP bit 2)
To safeguard keys from being accessed by end-users, enabling the MP bit prevents the CPU from reading keys.
Modify bit 2 to 1 and then press "Write."
4.5 Important Notes:
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Do not enable the MP bit for version A chips.
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Burning OTP bits is irreversible, and incorrect burns may render the chips unusable.
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