Alarmingly high voltage when no battery installed

I did:

  1. select “battery powered” on my development board.
  2. “forgot” to actually install the battery.
  3. Hooked up the board with the recommended programmer (the one from the cy8ckit-147).
  4. Hit F5 to start debugging
  5. Measured voltage between the arduino headers 3.3v and gnd.

The reading was 3.56v. The USB voltage was 4.95v

One might say the 3.56v is close to the limits of the onethinx module.

It might be a good idea with a level-shifter between programmer and module.

On which pin of the Arduino header did you measure 3.56V?

The arduino header pin labeled 3v3

Dropped a little before I managed to get a shot of it

That’s not okay, should be 3.0V or 3.3V (we had some kits with the 3V regulator).

Can you check the regulator?

:laughing: :rofl:

I experimented a little more and see it doesn’t matter if I have the power pins in battery or programmer mode.

The same happens.

If the programmer is idle - module just plugged in - voltage is stable around 3.02v. But when I start debugging it increases to 3.5v, peaks as high as 3.56v

Yes, now I remember. Could you try this modification on the programmer? It seems voltages of the SWD pins are too high.

Remove D1 from the Kitprog and solder 2x 1N400x in parallel to Vtarg.

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Two pcs 1448 diodes in series solved that. Now programming voltages are just below 3v.

Now, the other programmer I have also is a kitprog2, but the board has a slightly different layout, D1 is located on the top side. Anyway, is appears to have the same connections so I assume it will be safe to mod that one too.

Yes, if D1 is in series with Vbus and Vtarg then it’s okay.