stm32f4 random hard faults (solved)

Posted on April 10, 2012 at 23:05

Hi all,

With Keil MDK-ARM I had a random hard fault when I change the optimization level of the compiler.

The reason is a VPUSH.64 assembler instruction that tries to use the FPU. This instruction is added by the compiler before entering the main() function, so, at this point, the PFU is not enable.

I found a solution at http://e2e.ti.com/support/microcontrollers/stellaris_arm_cortex-m3_microcontroller/f/471/t/155025.aspx?PageIndex=2

Edit startup_stm32f4xx.s file and add the following code in the Reset_handler

                ; CPACR is located at address 0xE000ED88

                LDR.W   R0, =0xE000ED88

                ; Read CPACR

                LDR     R1, [R0]

                ; Set bits 20-23 to enable CP10 and CP11 coprocessors

                ORR     R1, R1, ♯(0xF << 20)

                ; Write back the modified value to the CPACR

                STR     R1, [R0]; wait for store to complete

                DSB

                ;reset pipeline now the FPU is enabled

                ISB

Regrds,

�ngel

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