I was designing PCBs with STM32 blue pill, but I need to design without blue pill, so I will need an STM32F103C8T6.

Do I need both resonators? I read that one of them is for LSE and the other is HSE resonator. Do I really need to use both?

My resonator design on EasyEDA

  • 1
    \$\begingroup\$ What does you PCB do? \$\endgroup\$
    – Rodo
    Commented Feb 5 at 17:59
  • \$\begingroup\$ Using temperature values via pt100 and max31865 and controlling 3 each relays \$\endgroup\$
    – Akinci
    Commented Feb 5 at 18:27

1 Answer 1


No, you might not need any crystals, because it depends on what you are using them for, and if you don't need to use them for anything then there is no point adding them to the circuit.

Whether or not you need any crystals is dependent on what your MCU has to do, and how precise clocks it needs to do what it has to do within specs or otherwise properly.

  • \$\begingroup\$ My MCU will control relays and reading temperature values from max31865. I dont think that I will need it. right? \$\endgroup\$
    – Akinci
    Commented Feb 5 at 18:51
  • \$\begingroup\$ @Akinci No, that certainly does not require accurate timing. It would be completely different if you used a communication interface which requires a crystal for accuracy, such as UART or USB. \$\endgroup\$
    – Justme
    Commented Feb 5 at 19:29
  • \$\begingroup\$ I will use FTDI programmer to upload codes. Still doesn' need? \$\endgroup\$
    – Akinci
    Commented Feb 5 at 22:01
  • \$\begingroup\$ @Akinci Factory bootloader does not require a crystal.. It uses the built-in oscillator with autobaud. \$\endgroup\$
    – Justme
    Commented Feb 6 at 5:02

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