i am using St32f429BITx controller evaluation board. when i programmed it using ST-link then it programmed easily, no problem there but after program when i check the output(even toggle a single PIN) then it not functioning.I dont understand the problem. Also there is no frequency on the Crystal pins, i changed the crystal twice but no effect, if there anyone who knows this problem please tell.
Note that lots of processors supports multiple alternative oscillators. So they may boot with an internal RC oscillator. Then if the program explicitly requests the use of an external crystal oscillator will it be spun up.
So when the crystal doesn't oscillate, the first step is to figure out if the program actually configures the crystal oscillator. It takes less power to run on an RC oscillator - but the RC oscillator has lower precision which is why lots of programs must have a crystal oscillator.
An internal RC oscillator can be exact enough for UART communication, but isn't exact enough for a real-time clock, or for USB or CAN communication.