In this guide, we will step-by-step guide you to use OPTTool (a software application) to burn OTP bits on SP7350 platforms.
...
| Table of Contents | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
1. Prerequisites:
Before proceeding, ensure that your SP7350 code is compiled to support the OTPTool. Confirm that both the “OTP driver” and “OTP driver handshake” options in X-Boot are enabled. To do this:
...
If the options are not enabled, enable them and save the changes. Run the command ‘make' in the project’s top directory to rebuild the code.
2. UART Connection Setup
2.1 Close Terminal Applications
Close terminal applications such as Putty to free up the COM port connected to the SP7350 platform.
2.2 Run OTPTool
Launch "OTPTool V1.0.0.0.exe" on your PC. Once started, the application interface will be displayed as shown below:
...
2.3 Configure COM Port
Set the COM port connected to the SP7350 platform. Refer to screenshot below:
...
The status window of OTPTool indicates "CONNECT Success!" as shown above.
3 OTPTool Operations:
3.1 Open Excel File (OTP table)
...
The status window of OTPTool indicates "READ Start..…” and then “READ Success!" as shown above.
3.3 Write to OTP Bits
...
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:
...
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:
...
The status window of the OTPTool indicates "WRITE Start..…” and then “WRITE Success!" as shown above.
Press 'Read' to read back content of OTP.
...
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:
...
The status window of the OTPTool indicates "WRITE Start..…” and then “WRITE Success!" as shown above.
Press 'Read' to confirm the content of OTP.
...
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."
...
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:
Do not enable the MP bit for version A chips.
Burning OTP bits is irreversible, and incorrect burns may render the chips unusable.
Remember to save the keys in designated directories (hsm_keys, otp_Sb_keys, and otp_Device_keys).