Add disco_f411ve

[TomSaw]

Quite an old board i found behind the fridge. Very similar to disco_f407vg despite different clocks and PLL factors.

It's the only board in the modm collection featuring a stm32f411vet6, hence the clock and PLL constants maybe worth being stored.

[salkinium]

Thanks! Do you want to try the USB example on this one? Should be almost identical to the F407 disco.

[salkinium]

Is this correct?

[TomSaw]

I've setup a PWM on Timer10 and Timer11, confirmed the output frequency and looks fine.

But could not make USB / TinyUSB working.
Please give me some advice!

Observations:

• Power on without Usb-Cable, Leds blink period = 2.5s -> Seems to be the initial default
• Connecting an Usb-Cable, the Leds blink period remains at 2.5s -> tud_mount_cb() not invoked.
• However, when disconnecting the Usb-Cable, the blink period changes to 250ms -> tud_umount_cb() invoked!
• Reconnecting the cable again, changes nothing. The blink period remains at 250ms.
• Only a reset gets me back to 2.5s right now.

[salkinium]

That's cos the USB is running at 50MHz and not 48MHz, hence my question about whether this clock is correct ;-P It probably works for a short time, but then gets out of sync.

CubeMX shows this solution running the CPU at 96MHz and USB at 48MHz:

[salkinium]

Actually, the /Q prescaler isn't set at all, so the USB probably runs at 100MHz or something completely wrong.

[TomSaw]

Ok, i have not really tried to iunderstand the clock system yet. So i got a copy of CubeMX as it looks like an usefull reference. Have seen this graphical configurator before but your screenshot finally convinced me to give it a closer look, thanks!

USB now works 😄

[salkinium]

I swapped the prescalers to align with the CubeMX solution, so the CPU now runs at 96MHz and the USB still at 48MHz.

[TomSaw]

The PLL statements in all board.hpp could be moved above the SystemClock struct to calculate
SystemClock::Frequency and SystemClock::Usb

👉🏾 This would document the causality and the "...Usb requires 48Mhz..." assertion somewhere else in modm would have catched me!

Something like this:

static constexpr uint32_t CrystalHSE = 8;
const Rcc::PllFactors pllFactors {
   ...
}

static constexpr uint32_t MainPllClock = CrystalHSE / PllFactors.pllM * PllFactors.pllN;

static constexpr uint32_t SystemClock::Frequency = MainPllClock / PllFactors.pllP;
static constexpr uint32_t SystemClock::Usb = MainPllClock / PllFactors.pllQ;

[salkinium]

Ohhhhhhh, that's an excellent idea!!! I'll merge this first, then prototype it. We can probably also put the AHB/APB prescalers in there.

[TomSaw]

Something easy, to build up 'momentum of success' will also support my motivational chemistry to complete the old graphic related PRs.

[TomSaw]

I've quickly sketched this in #1137