Hardfault error Float

Place an #error directive into the conditional part and compile - it should throw an error.

Step through disassembly of that code and observe how the register changes.

JW

There is some times a chicken-egg issue here. In the original CMSIS model you would enable the FPU in SystemInit() and this would be called during startup.s prior too calling main()

If main() pushes the FPU registers onto the stack, and you only initialize the FPU from within main(), you'll get a fault.

Some times you want to initialize the FPU CP10/CP11 in assembler, at the very beginning of Reset_Handler

https://community.st.com/s/question/0D50X00009XkY61SAF/stm32f4-fpu-question

Are you sure you are using an authentic part?

//****************************************************************************
 
void CORECheck(void) // sourcer32@gmail.com
{
 uint32_t cpuid = SCB->CPUID;
 uint32_t var, pat;
 
 printf("CPUID %08X DEVID %03X REVID %04X\n", cpuid, DBGMCU->IDCODE & 0xFFF, (DBGMCU->IDCODE >> 16) & 0xFFFF);
 
 pat = (cpuid & 0x0000000F);
 var = (cpuid & 0x00F00000) >> 20;
 
 if ((cpuid & 0xFF000000) == 0x41000000) // ARM
 {
 switch((cpuid & 0x0000FFF0) >> 4)
 {
 case 0xC20 : printf("Cortex M0 r%dp%d\n", var, pat); break;
 case 0xC60 : printf("Cortex M0+ r%dp%d\n", var, pat); break;
 case 0xC21 : printf("Cortex M1 r%dp%d\n", var, pat); break;
 case 0xC23 : printf("Cortex M3 r%dp%d\n", var, pat); break;
 case 0xC24 : printf("Cortex M4 r%dp%d\n", var, pat); break;
 case 0xC27 : printf("Cortex M7 r%dp%d\n", var, pat); break;
 
 default : printf("Unknown CORE\n");
 }
 }
 else
 printf("Unknown CORE IMPLEMENTER\n");
}
 
//****************************************************************************
 
// FPU Programmer Model
// http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0489b/Chdhfiah.html
 
void FPUCheck(void) // sourcer32@gmail.com
{
 uint32_t mvfr0;
 
 printf("%08X %08X %08X\n%08X %08X %08X\n",
 *(volatile uint32_t *)0xE000EF34, // FPCCR 0xC0000000
 *(volatile uint32_t *)0xE000EF38, // FPCAR
 *(volatile uint32_t *)0xE000EF3C, // FPDSCR
 *(volatile uint32_t *)0xE000EF40, // MVFR0 0x10110021 vs 0x10110221
 *(volatile uint32_t *)0xE000EF44, // MVFR1 0x11000011 vs 0x12000011
 *(volatile uint32_t *)0xE000EF48); // MVFR2 0x00000040
 
 mvfr0 = *(volatile uint32_t *)0xE000EF40;
 
 switch(mvfr0)
 {
 case 0x00000000 : puts("No FPU"); break;
 case 0x10110021 : puts("FPU-S Single-precision only"); break;
 case 0x10110221 : puts("FPU-D Single-precision and Double-precision"); break;
 default : puts("Unknown FPU");
 }
}
 
//****************************************************************************
 
void IDCODECheck(void) // sourcer32@gmail.com
{
 uint32_t idcode = DBGMCU->IDCODE & 0xFFF;
 
 switch(idcode)
 {
 case 0x423 :
 case 0x433 : printf("STM32F401\n"); break;
 case 0x431 : printf("STM32F411\n"); break;
 case 0x411 : printf("STM32F457\n"); break;
 case 0x413 : printf("STM32F407\n"); break;
 case 0x419 : printf("STM32F429 or F439\n"); break;
 case 0x421 : printf("STM32F446\n"); break;
 case 0x434 : printf("STM32F469\n"); break;
 case 0x441 : printf("STM32F412\n"); break;
 case 0x440 : printf("STM32F030x8\n"); break;
 case 0x442 : printf("STM32F030xC\n"); break;
 case 0x444 : printf("STM32F030x4 or F030x6\n"); break;
 case 0x445 : printf("STM32F070x6\n"); break;
 case 0x448 : printf("STM32F070x8\n"); break;
 case 0x417 : printf("STM32L0 Cat 3\n"); break;
 case 0x447 : printf("STM32L0 Cat 5\n"); break;
 case 0x435 : printf("STM32L43xxx or L44xxx\n"); break;
 case 0x415 : printf("STM32L475xx, L476xx or L486xx\n"); break;
 case 0x461 : printf("STM32L496xx or L4A6xx\n"); break;
 case 0x462 : printf("STM32L45xxx or L46xxx\n"); break;
 case 0x470 : printf("STM32L4Rxxx or L4Sxxx\n"); break;
 case 0x449 : printf("STM32F74xxx or F75xxx\n"); break;
 case 0x451 : printf("STM32F76xxx or F77xxx\n"); break;
 case 0x452 : printf("STM32F72xxx or F73xxx\n"); break;
 case 0x450 : printf("STM32H7xx\n"); break;
 default : printf("Unknown STM32\n");
 }
}
 
//****************************************************************************