Measurement Probe SMA Connection Prevents STM32F303 Target From Powering on CW308

1

Hello,

I’m using a ChipWhisperer-Lite with a CW308 UFO board and the STM32F303 target, and I’ve run into a problem where the STM32F303 won’t power up if the measurement probe is connected.

Current setup:

  • CW-Lite powered and connected via micro-USB
  • CW308 connected via the 20-pin to the CW-Lite
  • Measurement probe connected from CW-Lite MEASURE to J17 on the CW308
  • No external 5 V DC supply (waiting on one - it nay be a brown out/the CW-Lite can’t supply enough power)
  • Target powered via CW-Lite 3.3 V

CW308 jumper settings:

  • J4 – 3.3V (CW3.3V)
  • J3 – HS2/OUT
  • J14 – FILT/FILT_LP/FILT_HP
  • J16 – No connection
  • S1 – On or Auto
  • 3.3V SRC – J1/CW
  • VADJ SRC – 3.3V
  • 1.2V, 1.8V, 2.5V, 3.3V, LDO SRC – J1/CW
  • 5V SRC – DC

Behavior:

  • With the measurement probe connected: the STM32F303 target does not power up (LED2 and LED3 stay off, no SWD connection possible).
  • With the probe disconnected: the target powers up correctly (LED2/LED3 illuminate) and programming via SWD works.

Question:

  • What is the correct way to connect the measurement probe so I can capture power traces without preventing the STM32F303 target from powering?
  • Should J16 (SH-↔SH+) be populated while programming, and only removed when actually measuring?
  • Are there specific ChipWhisperer-Lite measurement settings (e.g., AC-coupling, high-Z input) required to avoid loading the rail?
  • Is an external 5 V supply required in this setup, or should powering the target from the CW-Lite 3.3 V be sufficient?

Thanks in advance for the guidance!

2

There should be very minimal loading from the measurement port, definitely nothing that would cause this. Could there be some sort of damage to your SMA cable? Can you try:

  1. Programming with the SMA plugged into J17, but not the Lite
  2. Programming with the SMA plugged into the Lite, but not J17

Also if you have a multimeter handy, can you try measuing the voltage between SHUNTL and ground when you’re having power issues?

Alex

3

So both of these are true:

  1. Programming with the SMA plugged into J17, but not the Lite
  2. Programming with the SMA plugged into the Lite, but not J17

It works as long as this connection isn’t made.

When the SMA is connected I get 0 volts between shuntil and ground.
When the SMA is disconnected I get 3.19 between shuntil and ground.

4

So it looks like there is something wrong with the SMA cables. They are pulling themselves to ground. If I wire conductor to conductor I don’t get the issue. Its the same behavior as pulling the conductor to ground.

5

Just validated its both of the cables that came in the kit. Basically both of them have continuity from the connection to the conductor. I’ll get some new cables. Hopefully this helps someone else.