When powering a F3Discovery (rev.D) board through the USB-USER port, there is a 2 second gap in the MCO clock signal (coming form the ST-LINK chip). See sceenshot1 (ch1=5V , ch2=MCO at SB12). When power is applied there is about 20ms worth of clock-cycles, then a gap of 2 seconds....
When powering the board with the USB ST-LINK, the gap is much shorter (about 300ms).... see screenshot2.
When using a F3Discovery (rev.B) the MCO clock has no dropout! See screenshot3.
Version of the ST-LINK firmware is latest 'V2.J34.M25 STM Debug + VCP)'.
The rev.B board has 'V2.J25.S0 STM Debugger', that I don't want to update, it might also start dropping the MCO-clock.
Because of this huge gap in the clock, plugging-in a USB-device (in Windows) gives your the dreaded 'Device Not Recognized'-errors. Running the same FW on the rev.b. works perfectly!
Thought I might share this information, anybody seen this as-well?
Best Regards,
Seynen
