CM4 with FPU that won't be used

Kernel
1

user-andrey wrote on Thursday, 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.

2

hs2sf wrote on Thursday, January 17, 2019:

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

3

user-andrey wrote on Thursday, 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.

4

rtel wrote on Thursday, 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).

5

user-andrey wrote on Tuesday, January 22, 2019:

Hello,

Thanks for the help.

Best regards.