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CM4 with FPU that won't be used

Posted by user-andrey on January 17, 2019

Hello,

I'm using STM32L4XX, this is a CM4 processor with FPU. In my project FPU is not needed and won't be used, I'm compiling with -mfloat-abi=soft option to ensure my compiler won't generate FPU instructions.

I've read on the forum that CM3 port can be used if CM4 processor doesn't have FPU. Can I use CM3 port?

FreeRTOS port for CM4F forces FPU activation, if I still want to use the CM4F port, can I disable the FPU after the scheduler starts?

I assume CM4F port suits better CM4 processors than CM3 port...

Thanks in advance. Best regards.


CM4 with FPU that won't be used

Posted by hs2sf on January 17, 2019

If you don't need the FPU the CM3 port is the right one even for CM4 MCUs.


CM4 with FPU that won't be used

Posted by user-andrey on January 17, 2019

Hello,

Thanks for the reply.

From the curiosity, what will happen, if I'll disable FPU after scheduler starts using CM4F port?

Best regards.


CM4 with FPU that won't be used

Posted by rtel on January 17, 2019

You will probably get an exception. If you are using the CM3 port on a CM4 chip then leave the FPU disabled (which it is by default).


CM4 with FPU that won't be used

Posted by user-andrey on January 22, 2019

Hello,

Thanks for the help.

Best regards.


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