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We use NXP MCUs that have a few different code protection modes. The mode we use in release code disables JTAG and Flash access, but allows erasing the entire F

by m_eiman 11y ago

We use NXP MCUs that have a few different code protection modes. The mode we use in release code disables JTAG and Flash access, but allows erasing the entire Flash. This makes it hard(er?) to read and modify our code, while still allowing us to easily wipe a returned device and re-program it using a suitable firmware image. Selecting which mode to use is a simple matter of setting a specific value at a specific position in the Flash image, very handy.

duskwuff 11y ago
The STM32F2 MCU that Amazon used supports similar features; see section 2.6.3 of: http://www.st.com/web/en/resource/technical/document/programming_manual/CD00233952.pdf http://www.st.com/web/en/resource/technical/document/program... In brief, though, the MCU can be put into "level 1" read protection which limits the capabilities of a JTAG debugger, or "level 2", which fully protects the device by disabling JTAG entirely. Given that Adafruit were able to reprogram the device, Amazon must not have used level 2 protection.