VREF issue while linking external board

i’m trying to attack an AES implementation running on a nucleo F401RE (https://www.st.com/en/evaluation-tools/nucleo-f401re.html). I’ve connected the board to the cw308 ufo board via J5 pin but the CW doesn’t detect it. The ufo board is linked to the CW-1200 with the 20-pin connector.

This is the error message from the jupyter:

Failed to detect chip. Check following:

  1. Connections and device power.
  2. Device has valid clock (or remove clock entirely for internal osc).
  3. On Rev -02 CW308T-STM32Fx boards, BOOT0 is routed to PDIC.

The external board is powered with a 5V VCC external supply.

  • should i link something to VREF (A20 pin) instead of default J4 setup?
  • what’s the minimal J5/J8/J13 subset needed to link a 5V external target board?

Thank you,

Hi Angelo,

I’m not familiar with this particular board, but it looks like it has a built-in programmer; have you tried programming your target through that instead of using ChipWhisperer to program it?

Other things to look into: using the CW308 STM32 target as an example, double check that all the connections to your target are correct. Useful links:


Hi Jean-Pierre,
thank you for the rapid answer.

I’ve just programmed the nucleo board through the built-in programmer (st-link) and it looks fine but i think i’m making some mistakes with decive power supply.

Looking on the CW308 Ufo target Wiki i read about the VREF network. It must be set up with the correct voltage level. CW308 targets works with a 3.3V power supply so the VREF is provided by the target… what about 5V targets? Any difference?

Thank you,

Are your target I/Os 5V?
If so you’ll need to use the CW506 for level shifting, as described here.