I am not actually using a STM32F4, I’m using a comparable chip by NXP (aka Freescale) from their K22 series.
But I don’t think there is much documentation on using ChipWhisperer with NXP devices, and my general concern was related to whether the ChipWhisperer was able to sample the power fast enough to handle a 120Mhz CPU.
e.g. Normally the STM32F4xx uses a 8 or 16Mhz clock (or similar values) and the internal PLL multplies that up to either 168 or 180Mhz etc depending on the specific F4 device.
So although the ChipWhisperer is providing the external clock, the actual instruction clock is much faster, and its likely to be executing at least 16 instructions for every clock cycle generated by ChipWhisperer
The STM32F4 derives its USB clock from its main clock, so you can’t adjust the external clock freq without changing the PLL settings, and of course thats not possible because memory mapped registers are locked.
So if the ChipWhisperer needs to run the MCU on a slower clock than the firmware is intended to run, then the USB host also needs to be slowed down to match.
I guess I can use another STM32F4 as a USB host, but I was hoping not to need to write host code in order to get the ChipWhisperer to analyze the current
However it looks increasing likely that I’ll need to do that 