STM32F7x[7,8,9] double prec FPU

[alex31]

A new stm32f7 line, with double precision FPU, is now available :
stm32F7X7 line

This line of products bring the long awaited double precision fpu, and (sounds weird to me, but i won't complain) it's cheaper that
the single precision version.

Is the support for this line is planned ? and if it is, for which chibios version is it scheduled ?

We will launch a new openhardware autopilot for opensource paparazzi project, we have prototype board with single prec
F7, but since double prec MCU is pin to pin compatible, it will allow us to run computing intensive filter that need double precision
for numerical stability.

Thanks
Alexandre

[Giovanni]

Hi,

As soon we get a board we will introduce support, the only difference should be in makefiles because the compiler must use another FPU mode.

Giovanni

[alex31]

the only difference should be in makefiles because the compiler must use another FPU mode.

Woah, this simple ?, ok, i can manage to try

I was thinking that something has to be done on the context saving side, fpu registers will be larger so the saving routine has to be adapted no ?

Code: Select all

As soon we get a board we will introduce support

We will order some 100 pins chip as they are available now, if disco boards with that chip are late,
i can send you one autopilot fitted with that chip as soon as we built it.

Alexandre

[Giovanni]

If I remember well double types simply take 2 registers.

Giovanni

[alex31]

You are right, so using fpv5-d16 instead fpv5-sp-d16 should be sufficient.

there will also be a need for a slight modification of .ld file since this new families have 512ko ram instead of 384ko.
With the new organisation of ld file, it will be easy.

ps: ST will soon reach the 640ko limit, does chibios plan to add a himem extension (joking of course)

Alexandre --

[Giovanni]

Of course, you will just need to add some .sys file to the project.

Giovanni

[Giovanni]

Hi,

I added a new option to modify FPU settings in STM32F7 makefiles.

Giovanni

[piers]

Thanks, I'm trying to get my hands on some STM32F767's, seems well worth the upgrade (I'm now using STM32F745).

[alex31]

Hello,

I have tried to port some stuff from nucleo F746 to nucleo F767, using master branch, and
i have met a strange bug : RTC works on F746 but not on F767.

there is infinite loop at init :

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 while ((RTCD1.rtc->ISR & RTC_ISR_INITF) == 0)

So, for a mystery reason, RTC_ISR_INITF bit did not rise.
I have compare cmsys files stm32f746xx.h and stm32f767xx.h, and for the RTC peripheral, it's exactly the same stuff.

To reproduce the bug, just enable RTC in halconf.h of the RT-STM32F767ZI-NUCLEO144 demo and flash it.

What is very strange is that all the fields of RTCD1.rtc structure are zeroed

can be because peripheral (or his RCC) is not enabled ?

Alexandre

[Giovanni]

Is the xtal present on the board? Is the RTC clock enabled?

Giovanni