안녕하세요 제가 STM32F103 을하면서 궁금한점이 생겼는데요
다름이아니고 시스템 클록을 최대치인 72MHZ로 설정을 하려고합니다. 설정하는 방법중 하나로써 HSE 와 PLL 을 사용하여서 HSE의 OSC_IN OSC_OUT 단자에 16 MHZ의 크리스털을 접속시킨뒤 PLL 을 사용해 4.5배로 체배해서 72MHZ의 CLK 을 시스템 클럭으로 사용하려고 하는데요
제가사용하고있는 보드에서 (NUCLEO-F103RB) Datasheet를 참고해보니 OSC_IN 과 OSC_OUT에 기본적으로 16MHZ 의 크리스털이 연결되있지가 않아서 제가 직접 외부 핀헤더로 연결을 시키려고해보니 외부핀헤더에 OSC_IN 과 OSC_OUT 핀이 없는것 같습니다. 그래서 주파수와 관련된 사항들을 읽어보니까 
 
OSC clock supply
There are four ways to configure the pins corresponding to external high-speed clock (HSE):
• MCO from ST-LINK: MCO output of ST-LINK MCU is used as input clock. This
frequency cannot be changed, it is fixed at 8 MHz and connected to
PF0/PD0/PH0-OSC_IN of the STM32 microcontroller.
The following configuration is needed:
– SB55 OFF and SB54 ON
– SB16 and SB50 ON
– R35 and R37 removed
• HSE oscillator on-board from X3 crystal (not provided): for typical frequencies and
its capacitors and resistors, refer to STM32 microcontroller datasheet. Refer to the
AN2867 Application note for oscillator design guide for STM32 microcontrollers.The X3
crystal has the following characteristics: 8 MHz, 16 pF, 20 ppm, and DIP footprint. It is
recommended to use 9SL8000016AFXHF0 manufactured by Hong Kong X'tals
Limited.
The following configuration is needed:
– SB54 and SB55 OFF
– R35 and R37 soldered
– C33 and C34 soldered with 20 pF capacitors
– SB16 and SB50 OFF
• Oscillator from external PF0/PD0/PH0: from an external oscillator through pin 29 of
the CN7 connector.
The following configuration is needed:
– SB55 ON
– SB50 OFF
– R35 and R37 removed
• HSE not used: PF0/PD0/PH0 and PF1/PD1/PH1 are used as GPIO instead of clock
The following configuration is needed:
– SB54 and SB55 ON
– SB16 and SB50 (MCO) OFF
– R35 and R37 removed
There are two possible default configurations of the HSE pins, depending on the version of the STM32 Nucleo board hardware.
The board version MB1136 C-01 or MB1136 C-02 is mentioned on the sticker, placed on the bottom side of the PCB.
The board marking MB1136 C-01 corresponds to a board, configured as HSE not used.
The board marking MB1136 C-02 (or higher) corresponds to a board, configured to use
ST-LINK MCO as clock input.
 
다음과같이 HSE를 사용하려면 보드에 soldering 이 되지않은 부분에 soldering 을 하고 저항이 붙지않은부분에 저항또한 soldering을 하라는것같은데 제가 직접 보드에 알맞는 저항이나 커패시터를 구입을해서 직접 땜을해야되는것인가요?? 아니면 SYSTEMCLK 을 72MHZ로 설정할수있는 다른 방법이 있는지 여쭈어봅니다.