I am using an NUCLEO-F429Zi to read a sensor over I2C. The application works correct. When the ST-Link is removed (cut away) from the board, the I2C connectivity fails. Any idea how to prevent this?

[ISant.1]

I am using an NUCLEO-F429Zi to read a MPU over I2C ( 2C1, PB8, PB9). The applications works correct. The sensor returns the correct values. When the ST-Link is removed (cut away) from the board, the power supply Vin , the I2C connectivity fails. It is still possible to program the board and to set and toggle the I2C pins (PB(, PB9).

[SSone.1]

If you are using external clock as a clock source, as I know there is no crystal in nucleo boards and external clock comes from st-link. So if you cut the st-link connection clock source goes away too. I am not sure too, It doesn't hurt if you just try to use internal clock.

[ISant.1]

Thank you for the answers ! The problem was as you said. A crystal on the board solved the problem.

[Tesla DeLorean]

Make sure it isn't reliant on HSE

Output diagnostics via USART or other means

Check there aren't any timing, or clock/pin settings, that are altered by the ST-LINK

[ISant.1]

Thank you for the answers ! The problem was as you said. A crystal on the board solved the problem.

[ISant.1]

Thank you for the answers ! The problem was as you said. A crystal on the board solved the problem.