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@Gordon,
Well the USB is actually not used by the F401 side of the board.
The F401 uses a serial link, USART2, to the detachable ST-LINK/V2-1 debugger/programmer.
The later is actually doing all of the USB enumeration and console output on the USB port so as to be an mbed platform...
The HSE, ironically, is not used by the "MB1136 C-01", which, I guess, explains why they run slowly.
This describes what happens at boot time, search for HSI.
I have to admit being reluctant to get this down with clocks on such a board.
You will understand it much better than I, as well as the example joined to speed up the NucleoF401RE without HSE.@Manxome,
Yes it runs at 84 Mhz: didn't check that with an oscilloscope but it keeps time acurately.
If you modify your Nucleo-F401RE to be alike an "MB1136 C-02", I think you should get the expected result: no software to change, just runs as is at 84 Mhz. The differences are explained in the DM00105823.pdf aka UM1724.pdf. Apparently mine is "MB1136 C-02" but it has a slight difference with the manual: SB54 is ON.
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asez73
@Manxome so you're saying that over 60 seconds it's out by 5.25? I guess mine may do the same as I only tested that it was roughly correct.
Interestingly my F401 board has just the black crystal (which is a 32k clock crystal - so not the high speed oscillator).
@asez73 it looks like probably the best method right now is to just use the HSI, which will work on all boards - and which we know the speed of.
I don't think there will be a huge problem - I think HSE is only really used because of USB.