General • How to write data to the OTP, configure OTP permissions, and retrieve that data only from signed firmware - RP2350

Greetings,

A few days ago I learned how to sign firmware, enable secure boot,
disable the SWD interface, and verify that only signed firmwares run,
while unsigned ones do not.

Now is the time to do something truly useful with OTP and signed firmware.


=>Let me explain the situation I desired to solve,

I have the firmware for a controller, which in turn requires
500 16-bit values ​​as initialization data for the control algorithm to actually function.

Without this data, the controller software is essentially useless;
it can't work without the model identification data.




1)The idea is to write these 500 values ​​somewhere in the OTP space
(where it won't affect the boot keys or other configurations residing there).

I read that writing these 500 values ​​can be done with Picotool: picotool otp set


2)Configure the permissions of the OTP area where these 500 values ​​are written
so that they can only be read by signed firmware and cannot be recovered with Picotool.


3)And lastly, I need to know how to read these OTP values ​​from the signed firmware on the RP2350.



Can you provide examples of how to perform the steps described? Are there already made examples regarding this same problem?


Thanks!

Statistics: Posted by masteries — Thu Feb 19, 2026 10:37 am

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