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While ARMv7-A does include the Thumb-2 subset used in ARMv7-M, the actually used instructions in ARMv7-A binaries will likely be pretty different from those used in ARMv7-M microcontrollers. For one example, microcontrollers rarely use NEON floating-point or vector instructions from ARMv7-A (Cortex-M4F has FPU but IIRC it’s single precision only). Conversely,...


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You are on the right lines with integer division. The first 3 instructions are reasonably clear - R2 after UMULL is the result of an integer division by 1.875 (= 0x100000000 / 0x88888889) the following MOV is then a further integer divide by 8 resulting in R2 now containing the original R3 divided by 15 (= 1.875 * 8) the first RSB is then a multiplication ...


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No, TCK doesn’t have to match the CPU clock. In fact its usual speed is in kilohertz, not megahertz. However, you likely won’t see it in the oscilloscope or logic analyzer because it is driven by the JTAG probe and not the CPU. Discovering the JTAG pins requires active probing using something like JTAGulator, you are unlikely to find it via passive ...


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as my previous answer was deleted (I'm guessing because it was not an answer per se) I've got more of an answer for you. the firmware does nothing to stop you from using UART to interact with it except require a login. root login is enabled for such an endeavor and you already have the password in the buildroot.config file. from there you'll need to dig into ...


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