how to disable fpu on freertos nrf52 project

RE: how to disable fpu on freertos nrf52 project

Elkana — Mon, 20 Aug 2018 06:59:40 GMT

The following thread explains how to disable the FPU:

https://devzone.nordicsemi.com/f/nordic-q-a/30103/freertos-on-nrf52810

RE: how to disable fpu on freertos nrf52 project

bjorn-spockeli — Wed, 13 Dec 2017 10:16:59 GMT

@lkanab (Elkana B): This originates from the ARM_CM4F port provided by FreeRTOS, so when we ported it to our nRF52832 we did not take into account that the user should be able to enable/disable the FPU.

RE: how to disable fpu on freertos nrf52 project

bjorn-spockeli — Wed, 13 Dec 2017 10:12:31 GMT

Our port was built using ARM_CM4F port provided by FreeRTOS itself where they have have the same behavior. I guess that the normal approach with freeRTOS would be to use CM3 port for CM4 without FPU if you do not want to use the HW FPU.

RE: how to disable fpu on freertos nrf52 project

Elkana — Wed, 13 Dec 2017 02:07:51 GMT

@bjorn, Could you explain why you want us to use FPU? I find it hard to believe that FreeRTOS port really requires FPU. It is probably a performance optimisation, so why won't you leave the decision to the client?

RE: how to disable fpu on freertos nrf52 project

Elkana — Wed, 13 Dec 2017 02:01:52 GMT

I understand your answer, but WHY the port requires FPU?

RE: how to disable fpu on freertos nrf52 project

liudijiang — Tue, 22 Aug 2017 03:29:41 GMT

FPU cost more current. we try to save more power, because the device is supported by battery @Bjørn Spockeli

RE: how to disable fpu on freertos nrf52 project

liudijiang — Thu, 17 Aug 2017 05:10:15 GMT

FPU cost more current. we try to save more power, because the device is supported by battery @Bjørn Spockeli

RE: how to disable fpu on freertos nrf52 project

bjorn-spockeli — Mon, 14 Aug 2017 11:25:03 GMT

@liudijiang: Could you explain why you want to disable the FPU?

RE: how to disable fpu on freertos nrf52 project

RK — Sat, 12 Aug 2017 02:29:43 GMT

You can't. That port was done with the expectation there's an FPU and it's enabled, hence the error message if you don't enable it. If you want to use it without FPU support, you'll need to change the port or port it yourself.