Nucleo无法连接上STM32的原因？

手上是Nucleo板，发现无法连接上，无法识别该MCU是STM32。

Open On-Chip Debugger 0.8.0 (2014-04-28-08:42)
Licensed under GNU GPL v2
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Info : This adapter doesn't support configurable speed
Info : STLINK v2 JTAG v21 API v2 SWIM v5 VID 0x0483 PID 0x374B
Info : using stlink api v2
Info : Target voltage: 3.250693
Info : stm32f3x.cpu: hardware has 6 breakpoints, 4 watchpoints
Info : accepting 'gdb' connection from 3333
Info : device id = 0x10016439
Warn : Cannot identify target as a STM32 family.
Error: auto_probe failed
Error: Connect failed. Consider setting up a gdb-attach event for the target to prepare target for GDB connect, or use 'gdb_memory_map disable'.
Error: attempted 'gdb' connection rejected