User manual

Hardware layout and configuration UM1724
22/49 DocID025833 Rev 3
5.7.2 OSC 32 kHz clock supply
There are two ways to manage the external low-speed clock (LSE):
 On-board oscillator (not provided): X2 crystal with the following characteristics:
32.768 kHz, 12.5 PF, 20 PPM, and SM308 footprint
The following configuration is needed:
– SB48, SB49 OFF
– R34 and R36 soldered.
– C31, C32 soldered with 10pF capacitors
Oscillator from external PC14: from external oscillator through the pin 25 of
CN7connector.
The following configuration is needed:
– SB48, SB49 ON
– R34 and R36 removed
If PC14 and PC15 are used as GPIOs instead of being used as clock:
– SB48 and SB49 are ON, and
– R34 and R36 are removed (default configuration).
5.8 USART communication
The USART interface of STM32 microcontroller on STM32 Nucleo board can be connected
to ST-LINK MCU, or STMicroelectronics Morpho connector or to Arduino connector. The
choice can be changed by setting the related solder bridges. By default the USART
communication between the target MCU and ST-LINK MCU is enabled in order to support
Virtual Com Port for mbed (SB13 and SB14 ON, SB62 and SB63 OFF). If the
communication between the target MCU and shield or extension board is required, SB62
and SB63 should be ON, SB13 and SB14 should be OFF.
Part number example: ETMB32.768B125B
Manufacturer: BEIJING JINGYUXING TECHNOLOGY Co., Ltd.
Website: http://en.jfvny.com/